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Re: [Xen-devel] [PATCH v2] xen/arm: platform: fix Raspberry Pi compatible string



Hi,

On 10/9/19 5:59 PM, Stewart Hildebrand wrote:
On Wednesday, October 9, 2019 11:30 AM, Julien Grall <julien.grall@xxxxxxx> 
wrote:
On 04/10/2019 01:47, Stewart Hildebrand wrote:
Both upstream [1] and downstream [2] Linux kernels use "brcm,bcm2711"
as the compatible string for Raspberry Pi 4. Add this string to our
platform compatible list.

Did the RPI foundation released any kernel with the old binding?

Sure, I see the following tags in their linux tree since initial RPi4
support until the binding was updated:
raspberrypi-kernel_1.20190709-1
raspberrypi-kernel_1.20190718-1
raspberrypi-kernel_1.20190819-1
raspberrypi-kernel_1.20190925-1

These correspond with their binary releases at [3], except the binary
releases also have an earlier 1.20190620+1 tag with RPi4 support.

However, even with Xen looking for bcm2838, you wouldn't be able to
grab one of those releases and boot without running into other issues.
You'd still need a couple of additional patches at [4]. Currently the
only way that I'm aware of to successfully boot into dom0 and launch
domU is to build the dom0 kernel from source with the extra patches
applied found at [4].

Is there any plan to upstream those patches?


If so, I am ok if we don't support the compatible in Xen (we don't have a
release with it yet!), but it would be worth mentioning in the commit message
that this is going to break for some users (TBD) so they need to upgrade.

See below for suggestion.

@Juergen: I would like to consider this patch for Xen 4.13. This is limited to
RPI4 and would avoid us to ship it with a compatible that is going to disappear.


The brcm,bcm2838 convention is abandoned. Remove it.

Rename the variables within the file to a rpi4_* prefix since the file
is meant to cover the Raspberry Pi 4 platform.

"If you are using a device tree with the old compatible string
brcm,bcm2838, you will need to upgrade your device tree to one that has
the new brcm,bcm2711 compatible string."

That's fine with me.

Cheers,

--
Julien Grall

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