[Freedreno] Whether A200 driver is supported by Linux Mainline Kernel

[Rob Clark]

On Wed, May 31, 2017 at 3:42 AM, abhijit <abhijitnaik27 at gmail.com> wrote:
> Hi,
>
> We are working on iMx53 Quick start board based on iMx53 application
> processor. As you know this has A200 GPU.
>
> If I see in the mainline kernel 4.11.3, there are no source files for A2XX
> GPU. Based on this I am assuming that the mainline doesn't have support for
> A2XX.
>
> However in kernel-msm git checkout from Freedreno, there are A2XX related
> source code. I wanted to know whether this code is tested one and reason for
> non-inclusion of this code in mainline kernel.

With the kgsl backend in libdrm_freedreno, the userspace mesa driver
can work with some specific of kgsl (drivers/gpu/msm) from downstream
kernel-msm tree.. that kind of involves some hacks that don't work
perfectly to fake implicit-sync.  And I think downstream api changed
over time, I don't think many have had much luck getting that working
on newer android kernel branches.

As far as upstream driver (drivers/gpu/drm/msm), no one has sent
patches, yet.  Someone would need to study the a2xx parts in
downstream kernel and figure out how to add that in drm/msm/adreno.
Since the gpummu is part of the gpu (rather than a separate iommu
block with iommu driver outside of drm/msm), that would also need to
be ported.  If you have a setup w/ the downstream kernel driver
working (for example on an old kernel), doing something approximately
like this[1] could be useful to log clock/regulator/register access.
The demsm tool in freedreno envytools tree[2] can decode the logged
registers to make it easier to read.

Note, there have been some mesa patches on userspace side to make
things work better on a20x variants (previously I only had a22x
devices), although I don't think I've seen those posted to mesa-devel
yet.

[1] https://github.com/freedreno/kernel-msm/commit/814a28f5cedc8621fe746b601dd51d5869931845
[2] https://github.com/freedreno/envytools/blob/master/rnn/demsm.c

BR,
-R

> Are there any pointers how I can go about it.
>
> Thank you very much :)
>
> Regards,
>     Abhijit
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