[RFC] Add genericarm64 MACHINE using upstream defconfig

From: Ross Burton <ross.burton@arm.com>

This is a new 64-bit "generic" Arm machine, that expects the hardware to
be SystemReady IR compatible. This is slightly forward-leaning as there's
not a _lot_ of SystemReady hardware in the wild, but most modern boards
are and the number will only grow.  Also, this is the only way to have a
'generic' machine as without standardised bootloaders and firmware it
would be impossible.

The base machine configuration isn't that exciting: it's a fully featured
machine that supports most things, booting via UEFI and an initramfs.

However, the kernel is more interesting.  This RFC uses the upstream defconfig
because unlike some other platforms, the arm64 defconfig is actively
maintained with the goal of being a 'boots on most hardware' configuration.
My argument is: why would we duplicate that effort?

The "linux-yocto way" is configuration fragments and after a week of
hair-pulling I do actually have fragments that boot on a BeaglePlay, but
to say this was a tiresome and frustrating exercise would be understating it.

So, a request for comments: is it acceptable to use the upstream defconfig in
a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
configs, but repeating the effort to fragmentise the configuration and then
also have it sufficiently modular that it can be used in pieces - instead of
just being a large file split up into smaller files - is a lot of effort for
what might end up being minimal gain.  My fear is we end up with a fragmented
configuration that can't be easily modified without breaking some platforms,
and badly copies what the defconfig already does.

Ross
---
 meta-yocto-bsp/README.hardware.md             |  7 +++++
 meta-yocto-bsp/conf/machine/genericarm64.conf | 26 +++++++++++++++++++
 .../linux/linux-yocto_6.6.bbappend            |  9 +++++++
 meta-yocto-bsp/wic/genericarm64.wks.in        | 11 ++++++++
 4 files changed, 53 insertions(+)
 create mode 100644 meta-yocto-bsp/conf/machine/genericarm64.conf
 create mode 100644 meta-yocto-bsp/wic/genericarm64.wks.in

On Wed, 2024-02-21 at 10:57 +0000, Ross Burton wrote:
> From: Ross Burton <ross.burton@arm.com>
> 
> This is a new 64-bit "generic" Arm machine, that expects the hardware to
> be SystemReady IR compatible. This is slightly forward-leaning as there's
> not a _lot_ of SystemReady hardware in the wild, but most modern boards
> are and the number will only grow.  Also, this is the only way to have a
> 'generic' machine as without standardised bootloaders and firmware it
> would be impossible.
> 
> The base machine configuration isn't that exciting: it's a fully featured
> machine that supports most things, booting via UEFI and an initramfs.
> 
> However, the kernel is more interesting.  This RFC uses the upstream defconfig
> because unlike some other platforms, the arm64 defconfig is actively
> maintained with the goal of being a 'boots on most hardware' configuration.
> My argument is: why would we duplicate that effort?

Can you point at the policy/process which decides how a config option
makes it in there?

> The "linux-yocto way" is configuration fragments and after a week of
> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> to say this was a tiresome and frustrating exercise would be understating it.
> 
> So, a request for comments: is it acceptable to use the upstream defconfig in
> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
> configs, but repeating the effort to fragmentise the configuration and then
> also have it sufficiently modular that it can be used in pieces - instead of
> just being a large file split up into smaller files - is a lot of effort for
> what might end up being minimal gain.  My fear is we end up with a fragmented
> configuration that can't be easily modified without breaking some platforms,
> and badly copies what the defconfig already does.

Let me play devils advocate.

I do understand it is a pain, equally, once you do have it working, it
is something you rarely have to touch again for a given board.

In the context of linux-yocto, I suspect we'd end up with a few board
specific lists of config options (fragments) that board *really* needs.
genericarm64 would end up as the sum of all those configs, plus any
other bits which you really want in a generic machine, presumably the
genericx86 machines have an idea of that.

The advantage here is that you give the users three options:

a) the kitchen sink upstream "systemready" defconfig
b) the genericarm64 machine defconfig which works most places and 
   is 'guaranteed' on our target test platforms
c) a machine targeted defconfig with only what a board needs

Developers/users end up in different places at different points in
there lifecycles. 

For in depth development, you might like to be able to cut the kernel
down so you'd not rebuilding tons of stuff you don't need/use/care
about each time, nor transferring it to a device during updates.

For a specific product release, you again might want to trim it down to
what it needs.

If you're shipping demo software, a full systemready image would be
much more appropriate.

I think it comes down to whether the fragments are usable and testable.
We have a list of targets we want this new machine to run on so lets
start with those, define genericarm64 as that set of fragments combined
plus the generic pieces linux-yocto adds, then go from there. If you
add a new machine to the test matrix, we add a new fragment. If someone
wants to add new config, they need to show a machine using it.

Cheers,

Richard

I'm quite simply a hard NACK on this.

Everyone can feel free to overrule me here, but I won't be able to
maintain this along with the other board that I test each -dev,
variant and -stable bump with.

There are tools, etc, that while gathering dust can help chop up a
config, and that's where we can spend the time, along with making sure
the fragments make sense and are usable.

We all agreed to hold the reference boards to a higher standard, and
now I see this. So as tired and frustrated as you say you are,
multiply that by two with me.

Cheers,

Bruce


On Wed, Feb 21, 2024 at 5:57 AM Ross Burton <ross.burton@arm.com> wrote:
>
> From: Ross Burton <ross.burton@arm.com>
>
> This is a new 64-bit "generic" Arm machine, that expects the hardware to
> be SystemReady IR compatible. This is slightly forward-leaning as there's
> not a _lot_ of SystemReady hardware in the wild, but most modern boards
> are and the number will only grow.  Also, this is the only way to have a
> 'generic' machine as without standardised bootloaders and firmware it
> would be impossible.
>
> The base machine configuration isn't that exciting: it's a fully featured
> machine that supports most things, booting via UEFI and an initramfs.
>
> However, the kernel is more interesting.  This RFC uses the upstream defconfig
> because unlike some other platforms, the arm64 defconfig is actively
> maintained with the goal of being a 'boots on most hardware' configuration.
> My argument is: why would we duplicate that effort?
>
> The "linux-yocto way" is configuration fragments and after a week of
> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> to say this was a tiresome and frustrating exercise would be understating it.
>
> So, a request for comments: is it acceptable to use the upstream defconfig in
> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
> configs, but repeating the effort to fragmentise the configuration and then
> also have it sufficiently modular that it can be used in pieces - instead of
> just being a large file split up into smaller files - is a lot of effort for
> what might end up being minimal gain.  My fear is we end up with a fragmented
> configuration that can't be easily modified without breaking some platforms,
> and badly copies what the defconfig already does.
>
> Ross
> ---
>  meta-yocto-bsp/README.hardware.md             |  7 +++++
>  meta-yocto-bsp/conf/machine/genericarm64.conf | 26 +++++++++++++++++++
>  .../linux/linux-yocto_6.6.bbappend            |  9 +++++++
>  meta-yocto-bsp/wic/genericarm64.wks.in        | 11 ++++++++
>  4 files changed, 53 insertions(+)
>  create mode 100644 meta-yocto-bsp/conf/machine/genericarm64.conf
>  create mode 100644 meta-yocto-bsp/wic/genericarm64.wks.in
>
> diff --git a/meta-yocto-bsp/README.hardware.md b/meta-yocto-bsp/README.hardware.md
> index a8f38cb21a6..58ebc328b56 100644
> --- a/meta-yocto-bsp/README.hardware.md
> +++ b/meta-yocto-bsp/README.hardware.md
> @@ -29,6 +29,7 @@ The following boards are supported by the meta-yocto-bsp layer:
>
>    * Texas Instruments Beaglebone (beaglebone-yocto)
>    * General IA platforms (genericx86 and genericx86-64)
> +  * General 64-bit Arm SystemReady platforms (genericarm64)
>
>  For more information see the board's section below. The appropriate MACHINE
>  variable value corresponding to the board is given in brackets.
> @@ -126,6 +127,12 @@ USB Device:
>         dd command to write the image to a USB stick.
>
>
> +SystemReady Arm Platforms
> +=========================
> +
> +TODO
> +
> +
>  Texas Instruments Beaglebone (beaglebone-yocto)
>  ===============================================
>
> diff --git a/meta-yocto-bsp/conf/machine/genericarm64.conf b/meta-yocto-bsp/conf/machine/genericarm64.conf
> new file mode 100644
> index 00000000000..2ea270d8b06
> --- /dev/null
> +++ b/meta-yocto-bsp/conf/machine/genericarm64.conf
> @@ -0,0 +1,26 @@
> +#@TYPE: Machine
> +#@NAME: genericarm64
> +#@DESCRIPTION: Generic Arm64 machine for typical SystemReady platforms, which
> +#have working firmware and boot via EFI.
> +
> +require conf/machine/include/arm/arch-armv8a.inc
> +
> +# Arm Base System Architecture says v8.0+ is allowed, but FEAT_CRC32 is required
> +DEFAULTTUNE = "armv8a-crc"
> +
> +MACHINE_FEATURES = "acpi alsa bluetooth efi keyboard pci qemu-usermode rtc screen usbhost vfat wifi"
> +
> +# Install all the kernel modules and all the firmware
> +MACHINE_EXTRA_RRECOMMENDS += "kernel-modules linux-firmware"
> +
> +KERNEL_IMAGETYPE = "Image"
> +PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
> +INITRAMFS_IMAGE ?= "core-image-initramfs-boot"
> +
> +IMAGE_FSTYPES ?= "wic"
> +WKS_FILE ?= "genericarm64.wks.in"
> +
> +EFI_PROVIDER ?= "${@bb.utils.contains("DISTRO_FEATURES", "systemd", "systemd-boot", "grub-efi", d)}"
> +
> +# Try to bring up one physical serial console, or a virtualized serial console
> +SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
> diff --git a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> index 8e465c241e8..18f95de348f 100644
> --- a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> +++ b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> @@ -1,19 +1,28 @@
>  KBRANCH:genericx86  = "v6.6/standard/base"
> +KBRANCH:genericarm64  = "v6.6/standard/base"
>  KBRANCH:genericx86-64  = "v6.6/standard/base"
>  KBRANCH:beaglebone-yocto = "v6.6/standard/beaglebone"
>
> +KMACHINE:genericarm64 ?= "genericarm64"
>  KMACHINE:genericx86 ?= "common-pc"
>  KMACHINE:genericx86-64 ?= "common-pc-64"
>  KMACHINE:beaglebone-yocto ?= "beaglebone"
>
> +SRCREV_machine:genericarm64 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:genericx86 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:genericx86-64 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:beaglebone-yocto ?= "332d4668fcc32826907d4f3c4938845206006089"
>
> +COMPATIBLE_MACHINE:genericarm64 = "genericarm64"
>  COMPATIBLE_MACHINE:genericx86 = "genericx86"
>  COMPATIBLE_MACHINE:genericx86-64 = "genericx86-64"
>  COMPATIBLE_MACHINE:beaglebone-yocto = "beaglebone-yocto"
>
> +LINUX_VERSION:genericarm64 = "6.6.15"
>  LINUX_VERSION:genericx86 = "6.6.15"
>  LINUX_VERSION:genericx86-64 = "6.6.15"
>  LINUX_VERSION:beaglebone-yocto = "6.6.15"
> +
> +# Use upstream defconfig for genericarm64
> +KBUILD_DEFCONFIG:genericarm64 = "defconfig"
> +KCONFIG_MODE:genericarm64 = "--alldefconfig"
> diff --git a/meta-yocto-bsp/wic/genericarm64.wks.in b/meta-yocto-bsp/wic/genericarm64.wks.in
> new file mode 100644
> index 00000000000..417d4d88104
> --- /dev/null
> +++ b/meta-yocto-bsp/wic/genericarm64.wks.in
> @@ -0,0 +1,11 @@
> +# short-description: Create an EFI disk image
> +# long-description: Creates a partitioned EFI disk image that the user
> +# can directly dd to boot media.
> +
> +part /boot --source bootimg-efi --sourceparams="loader=${EFI_PROVIDER},initrd=${INITRAMFS_IMAGE}-${MACHINE}.${INITRAMFS_FSTYPES}" --label boot --active --align 1024 --use-uuid
> +
> +part / --source rootfs --fstype=ext4 --label root --align 1024 --use-uuid
> +
> +part swap --size 44 --label swap --fstype=swap --use-uuid
> +
> +bootloader --ptable gpt --timeout=5 --append="rootwait rootfstype=ext4"
> --
> 2.34.1
>
>
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>

I should add that if just doing this for qemu is acceptable, I can take
over the task of creating the configuration fragments with what remains
for the week.

Are the MACHINE configs and everything else I need already in OE-core
or available somewhere that I can find ?

Bruce

On Wed, Feb 21, 2024 at 8:34 AM Bruce Ashfield via
lists.openembedded.org
<bruce.ashfield=gmail.com@lists.openembedded.org> wrote:
>
> I'm quite simply a hard NACK on this.
>
> Everyone can feel free to overrule me here, but I won't be able to
> maintain this along with the other board that I test each -dev,
> variant and -stable bump with.
>
> There are tools, etc, that while gathering dust can help chop up a
> config, and that's where we can spend the time, along with making sure
> the fragments make sense and are usable.
>
> We all agreed to hold the reference boards to a higher standard, and
> now I see this. So as tired and frustrated as you say you are,
> multiply that by two with me.
>
> Cheers,
>
> Bruce
>
>
> On Wed, Feb 21, 2024 at 5:57 AM Ross Burton <ross.burton@arm.com> wrote:
> >
> > From: Ross Burton <ross.burton@arm.com>
> >
> > This is a new 64-bit "generic" Arm machine, that expects the hardware to
> > be SystemReady IR compatible. This is slightly forward-leaning as there's
> > not a _lot_ of SystemReady hardware in the wild, but most modern boards
> > are and the number will only grow.  Also, this is the only way to have a
> > 'generic' machine as without standardised bootloaders and firmware it
> > would be impossible.
> >
> > The base machine configuration isn't that exciting: it's a fully featured
> > machine that supports most things, booting via UEFI and an initramfs.
> >
> > However, the kernel is more interesting.  This RFC uses the upstream defconfig
> > because unlike some other platforms, the arm64 defconfig is actively
> > maintained with the goal of being a 'boots on most hardware' configuration.
> > My argument is: why would we duplicate that effort?
> >
> > The "linux-yocto way" is configuration fragments and after a week of
> > hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> > to say this was a tiresome and frustrating exercise would be understating it.
> >
> > So, a request for comments: is it acceptable to use the upstream defconfig in
> > a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
> > configs, but repeating the effort to fragmentise the configuration and then
> > also have it sufficiently modular that it can be used in pieces - instead of
> > just being a large file split up into smaller files - is a lot of effort for
> > what might end up being minimal gain.  My fear is we end up with a fragmented
> > configuration that can't be easily modified without breaking some platforms,
> > and badly copies what the defconfig already does.
> >
> > Ross
> > ---
> >  meta-yocto-bsp/README.hardware.md             |  7 +++++
> >  meta-yocto-bsp/conf/machine/genericarm64.conf | 26 +++++++++++++++++++
> >  .../linux/linux-yocto_6.6.bbappend            |  9 +++++++
> >  meta-yocto-bsp/wic/genericarm64.wks.in        | 11 ++++++++
> >  4 files changed, 53 insertions(+)
> >  create mode 100644 meta-yocto-bsp/conf/machine/genericarm64.conf
> >  create mode 100644 meta-yocto-bsp/wic/genericarm64.wks.in
> >
> > diff --git a/meta-yocto-bsp/README.hardware.md b/meta-yocto-bsp/README.hardware.md
> > index a8f38cb21a6..58ebc328b56 100644
> > --- a/meta-yocto-bsp/README.hardware.md
> > +++ b/meta-yocto-bsp/README.hardware.md
> > @@ -29,6 +29,7 @@ The following boards are supported by the meta-yocto-bsp layer:
> >
> >    * Texas Instruments Beaglebone (beaglebone-yocto)
> >    * General IA platforms (genericx86 and genericx86-64)
> > +  * General 64-bit Arm SystemReady platforms (genericarm64)
> >
> >  For more information see the board's section below. The appropriate MACHINE
> >  variable value corresponding to the board is given in brackets.
> > @@ -126,6 +127,12 @@ USB Device:
> >         dd command to write the image to a USB stick.
> >
> >
> > +SystemReady Arm Platforms
> > +=========================
> > +
> > +TODO
> > +
> > +
> >  Texas Instruments Beaglebone (beaglebone-yocto)
> >  ===============================================
> >
> > diff --git a/meta-yocto-bsp/conf/machine/genericarm64.conf b/meta-yocto-bsp/conf/machine/genericarm64.conf
> > new file mode 100644
> > index 00000000000..2ea270d8b06
> > --- /dev/null
> > +++ b/meta-yocto-bsp/conf/machine/genericarm64.conf
> > @@ -0,0 +1,26 @@
> > +#@TYPE: Machine
> > +#@NAME: genericarm64
> > +#@DESCRIPTION: Generic Arm64 machine for typical SystemReady platforms, which
> > +#have working firmware and boot via EFI.
> > +
> > +require conf/machine/include/arm/arch-armv8a.inc
> > +
> > +# Arm Base System Architecture says v8.0+ is allowed, but FEAT_CRC32 is required
> > +DEFAULTTUNE = "armv8a-crc"
> > +
> > +MACHINE_FEATURES = "acpi alsa bluetooth efi keyboard pci qemu-usermode rtc screen usbhost vfat wifi"
> > +
> > +# Install all the kernel modules and all the firmware
> > +MACHINE_EXTRA_RRECOMMENDS += "kernel-modules linux-firmware"
> > +
> > +KERNEL_IMAGETYPE = "Image"
> > +PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
> > +INITRAMFS_IMAGE ?= "core-image-initramfs-boot"
> > +
> > +IMAGE_FSTYPES ?= "wic"
> > +WKS_FILE ?= "genericarm64.wks.in"
> > +
> > +EFI_PROVIDER ?= "${@bb.utils.contains("DISTRO_FEATURES", "systemd", "systemd-boot", "grub-efi", d)}"
> > +
> > +# Try to bring up one physical serial console, or a virtualized serial console
> > +SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
> > diff --git a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> > index 8e465c241e8..18f95de348f 100644
> > --- a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> > +++ b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> > @@ -1,19 +1,28 @@
> >  KBRANCH:genericx86  = "v6.6/standard/base"
> > +KBRANCH:genericarm64  = "v6.6/standard/base"
> >  KBRANCH:genericx86-64  = "v6.6/standard/base"
> >  KBRANCH:beaglebone-yocto = "v6.6/standard/beaglebone"
> >
> > +KMACHINE:genericarm64 ?= "genericarm64"
> >  KMACHINE:genericx86 ?= "common-pc"
> >  KMACHINE:genericx86-64 ?= "common-pc-64"
> >  KMACHINE:beaglebone-yocto ?= "beaglebone"
> >
> > +SRCREV_machine:genericarm64 ?= "332d4668fcc32826907d4f3c4938845206006089"
> >  SRCREV_machine:genericx86 ?= "332d4668fcc32826907d4f3c4938845206006089"
> >  SRCREV_machine:genericx86-64 ?= "332d4668fcc32826907d4f3c4938845206006089"
> >  SRCREV_machine:beaglebone-yocto ?= "332d4668fcc32826907d4f3c4938845206006089"
> >
> > +COMPATIBLE_MACHINE:genericarm64 = "genericarm64"
> >  COMPATIBLE_MACHINE:genericx86 = "genericx86"
> >  COMPATIBLE_MACHINE:genericx86-64 = "genericx86-64"
> >  COMPATIBLE_MACHINE:beaglebone-yocto = "beaglebone-yocto"
> >
> > +LINUX_VERSION:genericarm64 = "6.6.15"
> >  LINUX_VERSION:genericx86 = "6.6.15"
> >  LINUX_VERSION:genericx86-64 = "6.6.15"
> >  LINUX_VERSION:beaglebone-yocto = "6.6.15"
> > +
> > +# Use upstream defconfig for genericarm64
> > +KBUILD_DEFCONFIG:genericarm64 = "defconfig"
> > +KCONFIG_MODE:genericarm64 = "--alldefconfig"
> > diff --git a/meta-yocto-bsp/wic/genericarm64.wks.in b/meta-yocto-bsp/wic/genericarm64.wks.in
> > new file mode 100644
> > index 00000000000..417d4d88104
> > --- /dev/null
> > +++ b/meta-yocto-bsp/wic/genericarm64.wks.in
> > @@ -0,0 +1,11 @@
> > +# short-description: Create an EFI disk image
> > +# long-description: Creates a partitioned EFI disk image that the user
> > +# can directly dd to boot media.
> > +
> > +part /boot --source bootimg-efi --sourceparams="loader=${EFI_PROVIDER},initrd=${INITRAMFS_IMAGE}-${MACHINE}.${INITRAMFS_FSTYPES}" --label boot --active --align 1024 --use-uuid
> > +
> > +part / --source rootfs --fstype=ext4 --label root --align 1024 --use-uuid
> > +
> > +part swap --size 44 --label swap --fstype=swap --use-uuid
> > +
> > +bootloader --ptable gpt --timeout=5 --append="rootwait rootfstype=ext4"
> > --
> > 2.34.1
> >
> >
> >
> >
>
>
> --
> - Thou shalt not follow the NULL pointer, for chaos and madness await
> thee at its end
> - "Use the force Harry" - Gandalf, Star Trek II
>
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> -=-=-=-=-=-=-=-=-=-=-=-
>

On 21/02/2024 10:57, Ross Burton wrote:
> From: Ross Burton <ross.burton@arm.com>
> 
> This is a new 64-bit "generic" Arm machine, that expects the hardware to
> be SystemReady IR compatible. This is slightly forward-leaning as there's
> not a _lot_ of SystemReady hardware in the wild, but most modern boards
> are and the number will only grow.  Also, this is the only way to have a
> 'generic' machine as without standardised bootloaders and firmware it
> would be impossible.
> 
> The base machine configuration isn't that exciting: it's a fully featured
> machine that supports most things, booting via UEFI and an initramfs.
> 
> However, the kernel is more interesting.  This RFC uses the upstream defconfig
> because unlike some other platforms, the arm64 defconfig is actively
> maintained with the goal of being a 'boots on most hardware' configuration.
> My argument is: why would we duplicate that effort?
> 
> The "linux-yocto way" is configuration fragments and after a week of
> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> to say this was a tiresome and frustrating exercise would be understating it.
> 
> So, a request for comments: is it acceptable to use the upstream defconfig in
> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
> configs, but repeating the effort to fragmentise the configuration and then
> also have it sufficiently modular that it can be used in pieces - instead of
> just being a large file split up into smaller files - is a lot of effort for
> what might end up being minimal gain.  My fear is we end up with a fragmented
> configuration that can't be easily modified without breaking some platforms,
> and badly copies what the defconfig already does.

I am in favour of this - I think the "genericarm64" machine should use
the in-tree defconfig so that it can support the widest array of
hardware. If someone wants to trim down the kernel for a particular
platform then they should probably create a specific MACHINE anyway.

If we take the other approach of building up the kernel config from
fragments, how would we know that all SystemReady IR capable systems
will be supported? Yocto Project doesn't have the resources to test
every platform.

For the Renesas RZ SoCs I work on these days, the in-tree defconfig is
the configuration we test with the mainline kernel.

Thanks,

From: Paul Gortmaker <paulg@kernel.org>

[[RFC PATCH] Add genericarm64 MACHINE using upstream defconfig] On 21/02/2024 (Wed 10:57) ross.burton@arm.com wrote:

> From: Ross Burton <ross.burton@arm.com>
> 
> This is a new 64-bit "generic" Arm machine, that expects the hardware to
> be SystemReady IR compatible. This is slightly forward-leaning as there's
> not a _lot_ of SystemReady hardware in the wild, but most modern boards
> are and the number will only grow.  Also, this is the only way to have a
> 'generic' machine as without standardised bootloaders and firmware it
> would be impossible.
> 
> The base machine configuration isn't that exciting: it's a fully featured
> machine that supports most things, booting via UEFI and an initramfs.
> 
> However, the kernel is more interesting.  This RFC uses the upstream defconfig
> because unlike some other platforms, the arm64 defconfig is actively
> maintained with the goal of being a 'boots on most hardware' configuration.
> My argument is: why would we duplicate that effort?

I have no problem with the idea of a genericarm64, but the defconfig
approach is not the way to go.

> The "linux-yocto way" is configuration fragments and after a week of
> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
> to say this was a tiresome and frustrating exercise would be understating it.

Yes, if you start with a giant "defconfig" file and try and slowly chip
away at it, it can be frustrating and time consuming.  I never do that.

It is the same problem space as trying to turn core-image-full-cmdline
into core-image-minimal by removing one package at a time.  Always
easier to start with the bare minimum and then add stuff.

> So, a request for comments: is it acceptable to use the upstream defconfig in
> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic

In a word, the answer is "no".

Let me insert a bit of history here - darn near 20y ago now - when we
were just starting out with linux, we had BSPs on different kernel
versions, and worse - the use of flat monolithic "defconfig" type files
on a per BSP basis.  The latter was to be blunt, just crap.  There was
no uniformity across BSPs in the same "family" - where family would be
something like CGL back in the 2005 era.

One BSP might have built iso9660 fs, another one not. Or one enabled
some debug option and another one didn't.  The inconsistency was just
horrible and unbearable.  BSPs were screwing with options they had no
business touching.

After a couple years of that mess, I believe several of us (which
included Bruce and myself) had just about enough.  What we came up with
was isolating the board config to a select subset of hardware/driver
Kconfig options and the "platform" would handle "non-harware" options.

That largely is still what exists in Yocto today, even though we were
not using Yocto waaay back then.  It immediately brought consistency
across platforms, and a stark clarity to exactly what the board required
for Kconfig settings - typically less than a screen full - choose the
CPU and the driver for video and disk/flash and USB chip etc.  Compare
that to the unreadable 10,000+ lines in a defconfig now.

So, yes I'll grant you that making that one screen full of core hardware
settings can be frustrating.  But at the same time, it has also served
as a valuable filter.  If a person can't distill a BSP down into the
core options it *really* needs, then they typically either don't
understand the hardware, or are just not invested enough to go that
extra mile.  I'm not saying either is the case here - just in general.

On top of all that - we've had similar discussions before along similar
lines - where Yocto/OE are not RedHat or Ubuntu - where we try and
deliver a distro with "one config works everywhere" kind of stuff.

I'm fine with genericarm64 - but please please don't encourage the chaos
and madness associated with random unmaintainable defconfigs!  Just
because it exists upstream doesn't mean it is good.

Thanks,
Paul.

> configs, but repeating the effort to fragmentise the configuration and then
> also have it sufficiently modular that it can be used in pieces - instead of
> just being a large file split up into smaller files - is a lot of effort for
> what might end up being minimal gain.  My fear is we end up with a fragmented
> configuration that can't be easily modified without breaking some platforms,
> and badly copies what the defconfig already does.
> 
> Ross
> ---
>  meta-yocto-bsp/README.hardware.md             |  7 +++++
>  meta-yocto-bsp/conf/machine/genericarm64.conf | 26 +++++++++++++++++++
>  .../linux/linux-yocto_6.6.bbappend            |  9 +++++++
>  meta-yocto-bsp/wic/genericarm64.wks.in        | 11 ++++++++
>  4 files changed, 53 insertions(+)
>  create mode 100644 meta-yocto-bsp/conf/machine/genericarm64.conf
>  create mode 100644 meta-yocto-bsp/wic/genericarm64.wks.in
> 
> diff --git a/meta-yocto-bsp/README.hardware.md b/meta-yocto-bsp/README.hardware.md
> index a8f38cb21a6..58ebc328b56 100644
> --- a/meta-yocto-bsp/README.hardware.md
> +++ b/meta-yocto-bsp/README.hardware.md
> @@ -29,6 +29,7 @@ The following boards are supported by the meta-yocto-bsp layer:
>  
>    * Texas Instruments Beaglebone (beaglebone-yocto)
>    * General IA platforms (genericx86 and genericx86-64)
> +  * General 64-bit Arm SystemReady platforms (genericarm64)
>  
>  For more information see the board's section below. The appropriate MACHINE
>  variable value corresponding to the board is given in brackets.
> @@ -126,6 +127,12 @@ USB Device:
>         dd command to write the image to a USB stick.
>  
>  
> +SystemReady Arm Platforms
> +=========================
> +
> +TODO
> +
> +
>  Texas Instruments Beaglebone (beaglebone-yocto)
>  ===============================================
>  
> diff --git a/meta-yocto-bsp/conf/machine/genericarm64.conf b/meta-yocto-bsp/conf/machine/genericarm64.conf
> new file mode 100644
> index 00000000000..2ea270d8b06
> --- /dev/null
> +++ b/meta-yocto-bsp/conf/machine/genericarm64.conf
> @@ -0,0 +1,26 @@
> +#@TYPE: Machine
> +#@NAME: genericarm64
> +#@DESCRIPTION: Generic Arm64 machine for typical SystemReady platforms, which
> +#have working firmware and boot via EFI.
> +
> +require conf/machine/include/arm/arch-armv8a.inc
> +
> +# Arm Base System Architecture says v8.0+ is allowed, but FEAT_CRC32 is required
> +DEFAULTTUNE = "armv8a-crc"
> +
> +MACHINE_FEATURES = "acpi alsa bluetooth efi keyboard pci qemu-usermode rtc screen usbhost vfat wifi"
> +
> +# Install all the kernel modules and all the firmware
> +MACHINE_EXTRA_RRECOMMENDS += "kernel-modules linux-firmware"
> +
> +KERNEL_IMAGETYPE = "Image"
> +PREFERRED_PROVIDER_virtual/kernel ?= "linux-yocto"
> +INITRAMFS_IMAGE ?= "core-image-initramfs-boot"
> +
> +IMAGE_FSTYPES ?= "wic"
> +WKS_FILE ?= "genericarm64.wks.in"
> +
> +EFI_PROVIDER ?= "${@bb.utils.contains("DISTRO_FEATURES", "systemd", "systemd-boot", "grub-efi", d)}"
> +
> +# Try to bring up one physical serial console, or a virtualized serial console
> +SERIAL_CONSOLES ?= "115200;ttyAMA0 115200;hvc0"
> diff --git a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> index 8e465c241e8..18f95de348f 100644
> --- a/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> +++ b/meta-yocto-bsp/recipes-kernel/linux/linux-yocto_6.6.bbappend
> @@ -1,19 +1,28 @@
>  KBRANCH:genericx86  = "v6.6/standard/base"
> +KBRANCH:genericarm64  = "v6.6/standard/base"
>  KBRANCH:genericx86-64  = "v6.6/standard/base"
>  KBRANCH:beaglebone-yocto = "v6.6/standard/beaglebone"
>  
> +KMACHINE:genericarm64 ?= "genericarm64"
>  KMACHINE:genericx86 ?= "common-pc"
>  KMACHINE:genericx86-64 ?= "common-pc-64"
>  KMACHINE:beaglebone-yocto ?= "beaglebone"
>  
> +SRCREV_machine:genericarm64 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:genericx86 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:genericx86-64 ?= "332d4668fcc32826907d4f3c4938845206006089"
>  SRCREV_machine:beaglebone-yocto ?= "332d4668fcc32826907d4f3c4938845206006089"
>  
> +COMPATIBLE_MACHINE:genericarm64 = "genericarm64"
>  COMPATIBLE_MACHINE:genericx86 = "genericx86"
>  COMPATIBLE_MACHINE:genericx86-64 = "genericx86-64"
>  COMPATIBLE_MACHINE:beaglebone-yocto = "beaglebone-yocto"
>  
> +LINUX_VERSION:genericarm64 = "6.6.15"
>  LINUX_VERSION:genericx86 = "6.6.15"
>  LINUX_VERSION:genericx86-64 = "6.6.15"
>  LINUX_VERSION:beaglebone-yocto = "6.6.15"
> +
> +# Use upstream defconfig for genericarm64
> +KBUILD_DEFCONFIG:genericarm64 = "defconfig"
> +KCONFIG_MODE:genericarm64 = "--alldefconfig"
> diff --git a/meta-yocto-bsp/wic/genericarm64.wks.in b/meta-yocto-bsp/wic/genericarm64.wks.in
> new file mode 100644
> index 00000000000..417d4d88104
> --- /dev/null
> +++ b/meta-yocto-bsp/wic/genericarm64.wks.in
> @@ -0,0 +1,11 @@
> +# short-description: Create an EFI disk image
> +# long-description: Creates a partitioned EFI disk image that the user
> +# can directly dd to boot media.
> +
> +part /boot --source bootimg-efi --sourceparams="loader=${EFI_PROVIDER},initrd=${INITRAMFS_IMAGE}-${MACHINE}.${INITRAMFS_FSTYPES}" --label boot --active --align 1024 --use-uuid
> +
> +part / --source rootfs --fstype=ext4 --label root --align 1024 --use-uuid
> +
> +part swap --size 44 --label swap --fstype=swap --use-uuid
> +
> +bootloader --ptable gpt --timeout=5 --append="rootwait rootfstype=ext4"
> -- 
> 2.34.1
> 
>

On 2/21/24 9:06 AM, Paul Barker wrote:
> On 21/02/2024 10:57, Ross Burton wrote:
>> From: Ross Burton <ross.burton@arm.com>
>>
>> This is a new 64-bit "generic" Arm machine, that expects the hardware to
>> be SystemReady IR compatible. This is slightly forward-leaning as there's
>> not a _lot_ of SystemReady hardware in the wild, but most modern boards
>> are and the number will only grow.  Also, this is the only way to have a
>> 'generic' machine as without standardised bootloaders and firmware it
>> would be impossible.
>>
>> The base machine configuration isn't that exciting: it's a fully featured
>> machine that supports most things, booting via UEFI and an initramfs.
>>
>> However, the kernel is more interesting.  This RFC uses the upstream defconfig
>> because unlike some other platforms, the arm64 defconfig is actively
>> maintained with the goal of being a 'boots on most hardware' configuration.
>> My argument is: why would we duplicate that effort?
>>
>> The "linux-yocto way" is configuration fragments and after a week of
>> hair-pulling I do actually have fragments that boot on a BeaglePlay, but
>> to say this was a tiresome and frustrating exercise would be understating it.
>>
>> So, a request for comments: is it acceptable to use the upstream defconfig in
>> a reference BSP?  Personally I'm torn: the Yocto way is fragments not monolithic
>> configs, but repeating the effort to fragmentise the configuration and then
>> also have it sufficiently modular that it can be used in pieces - instead of
>> just being a large file split up into smaller files - is a lot of effort for
>> what might end up being minimal gain.  My fear is we end up with a fragmented
>> configuration that can't be easily modified without breaking some platforms,
>> and badly copies what the defconfig already does.
> 
> I am in favour of this - I think the "genericarm64" machine should use
> the in-tree defconfig so that it can support the widest array of
> hardware. If someone wants to trim down the kernel for a particular
> platform then they should probably create a specific MACHINE anyway.
> 
> If we take the other approach of building up the kernel config from
> fragments, how would we know that all SystemReady IR capable systems
> will be supported? Yocto Project doesn't have the resources to test
> every platform.

I disagree here.  I think it would be MUCH better to have a 'SystemReady IR' 
hardware configuration.  So if SystemReady IR is desired, it is something that 
anyone can enable (starting with genericarm64).  Remember the defconfig is going 
to have more then hardware configs in it.  Will it have the right systemd 
configurations?  Will is have the magic filesystem a random user wants?  Will 
avoid having some other filesystem type that another user doesn't want?

Building up the kernel, and considering SystemReady IR as a 'hardware feature', 
and then add in the additional things that are needed for whatever reason is a 
much more reasonable way to do this and make it useful to otthers.

> For the Renesas RZ SoCs I work on these days, the in-tree defconfig is
> the configuration we test with the mainline kernel.

AMD does the same thing, for the kernel development it makes sense.  Kernel is 
built and tested standalone from userspace.

But with that said, I think it's the wrong way to do Yocto Project development. 
Yocto Project development needs further control and the separation of hardware 
and software configurations is pretty essential to having a system that can be 
customized appropriately.

The defconfig can be used as a guide to the other configurations, but separating 
hardware and software configs is a necessary first step in my opinion.

--Mark

> Thanks,
> 
> 
> 
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