[Intel-gfx] [PATCH] drm/i915/gt: Limit VFE threads based on GT

[rwright at hpe.com]

On Fri, Oct 16, 2020 at 06:54:11PM +0100, Chris Wilson wrote:

> MEDIA_STATE_VFE only accepts the 'maximum number of threads' in the
> range [0, n-1] where n is #EU * (#threads/EU) with the number of threads
> based on plaform and the number of EU based on the number of slices and
> subslices. This is a fixed number per platform/gt, so appropriately
> limit the number of threads we spawn to match the device.
> 
> Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2024
> Fixes: 47f8253d2b89 ("drm/i915/gen7: Clear all EU/L3 residual contexts")
> Signed-off-by: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Prathap Kumar Valsan <prathap.kumar.valsan at intel.com>
> Cc: Akeem G Abodunrin <akeem.g.abodunrin at intel.com>
> Cc: Balestrieri Francesco <francesco.balestrieri at intel.com>
> Cc: Bloomfield Jon <jon.bloomfield at intel.com>
> Cc: <stable at vger.kernel.org> # v5.7+
> ---
> ...

I tested this patch and found that it prevents the GPU hang I had
reported on the HP Pavilion Mini 300-020 in
https://gitlab.freedesktop.org/drm/intel/-/issues/2413.

In more detail: I built linux-next at tag next-20201106 without
the patch, and booted the result on an Ubuntu 20.04 base system.  As
expected, I observed the hang that I had previously reported as soon as
Cinnnamon started when I entered graphical.target.

I then applied this patch - that being the only change to my kernel -
and I was able to boot to graphical.target 5 times consecutively without
any GPU hang.

You may add my endorsements:

Tested-by: Randy Wright <rwright at hpe.com>
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2413
Closes: https://gitlab.freedesktop.org/drm/intel/-/issues/2106

-- 
Randy Wright            Hewlett Packard Enterprise
Phone: (970) 898-0998   Mail: rwright at hpe.com