[PATCH 1/2] drm/i915: limit double GT reset to pre-MTL

[Andi Shyti]

Hi Daniele,

On Mon, Mar 20, 2023 at 02:10:38PM -0700, Daniele Ceraolo Spurio wrote:
> Commit 3db9d590557d ("drm/i915/gt: Reset twice") modified the code to
> always hit the GDRST register twice when doing a reset, with the
> reported aim to fix invalid post-reset engine state on some platforms
> (Jasperlake being the only one actually mentioned).
> 
> This is a problem on MTL, due to the fact that we have to apply a time
> consuming WA (coming in the next patch) every time we hit the GDRST
> register in a way that can include the GSC engine. Even post MTL, the
> expectation is that we'll have some work to do before and after hitting
> the GDRST if the GSC is involved.
> 
> Since the issue requiring the double reset seems to be limited to older
> platforms, instead of trying to handle the double-reset on MTL and
> future platforms it is just easier to turn it off. The default on MTL is
> also for GuC to own engine reset, with i915 only covering full-GT reset.
> 
> Signed-off-by: Daniele Ceraolo Spurio <daniele.ceraolospurio at intel.com>
> Cc: Chris Wilson <chris at chris-wilson.co.uk>
> Cc: Andi Shyti <andi.shyti at linux.intel.com>
> Cc: Mika Kuoppala <mika.kuoppala at linux.intel.com>
> Cc: Gwan-gyeong Mun <gwan-gyeong.mun at intel.com>
> Cc: John Harrison <John.C.Harrison at Intel.com>

Reviewed-by: Andi Shyti <andi.shyti at linux.intel.com>

Andi