[Intel-gfx] [PATCH] drm/i915: Transform WaInPlaceDecompressionHang to a simple reg write

[Oscar Mateo]

On 09/06/2017 02:43 PM, Chris Wilson wrote:
> Quoting Oscar Mateo (2017-09-06 22:27:47)
>>
>> On 09/06/2017 02:19 PM, Chris Wilson wrote:
>>> Quoting Oscar Mateo (2017-09-06 22:12:11)
>>>> Afaict, GEN9_GAMT_ECO_REG_RW_IA does not live in the context, so writing
>>>> it on every context creation is overkill (and wrong).
>>>>
>>>> Cc: Mika Kuoppala <mika.kuoppala at intel.com>
>>>> Cc: Rodrigo Vivi <rodrigo.vivi at intel.com>
>>>> Signed-off-by: Oscar Mateo <oscar.mateo at intel.com>
>>>> ---
>>>>    drivers/gpu/drm/i915/intel_engine_cs.c | 25 +++++++++++++++----------
>>>>    1 file changed, 15 insertions(+), 10 deletions(-)
>>>>
>>>> diff --git a/drivers/gpu/drm/i915/intel_engine_cs.c b/drivers/gpu/drm/i915/intel_engine_cs.c
>>>> index 23812ec..9f01a5c 100644
>>>> --- a/drivers/gpu/drm/i915/intel_engine_cs.c
>>>> +++ b/drivers/gpu/drm/i915/intel_engine_cs.c
>>>> @@ -985,8 +985,9 @@ static int skl_init_workarounds(struct intel_engine_cs *engine)
>>>>    
>>>>           /* WaInPlaceDecompressionHang:skl */
>>>>           if (IS_SKL_REVID(dev_priv, SKL_REVID_H0, REVID_FOREVER))
>>>> -               WA_SET_BIT(GEN9_GAMT_ECO_REG_RW_IA,
>>>> -                          GAMT_ECO_ENABLE_IN_PLACE_DECOMPRESS);
>>> Anything using a precalculated RMW value for a ctx register is indeed
>>> fishy. Whilst you are checking this register, can you check whether the
>>> other users of WA_SET_BIT/WA_CLR_BIT are indeed context bound?
>>> -Chris
>> Sure, I'll try to go through all of them (but I'd like to clarify first
>> if I should also be moving those I find to xxx_init_clock_gating).
> The short answer is probably not, init_clock_gating we expect to be
> targetting display w/a. There's not always a clear divide between GT and
> display, but we keep on muttering that we should keep them them as
> cleanly separated as possible so that we know where to look when
> different IP blocks are updated. (And yes the name is one of those
> things that we keep on waiting for someone else to fix.)
> -Chris

It's not only the name, there is even a comment saying non-context, 
non-WABB GT workarounds go here:

/**
  * intel_init_clock_gating_hooks - setup the clock gating hooks
  * @dev_priv: device private
  *
  * Setup the hooks that configure which clocks of a given platform can be
  * gated and also apply various GT and display specific workarounds for 
these
  * platforms. Note that some GT specific workarounds are applied separately
  * when GPU contexts or batchbuffers start their execution.
  */