Re: [PATCH v2 4/4] drm/i915/gen9: Add WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken

[Dave Gordon <david.s.gordon@intel.com>]

On 13/07/15 14:16, Mika Kuoppala wrote:
> Arun Siluvery <arun.siluvery@linux.intel.com> writes:
>
>> In Indirect context w/a batch buffer,
>> +WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken
>>
>> v2: SKL revision id was used for BXT, copy paste error found during
>> internal review (Bob Beckett).
>>
>> Cc: Robert Beckett <robert.beckett@intel.com>
>> Cc: Imre Deak <imre.deak@intel.com>
>> Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/intel_lrc.c        | 9 +++++++++
>>   drivers/gpu/drm/i915/intel_ringbuffer.c | 7 +++++--
>>   2 files changed, 14 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index 58247f0..61ed92b 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -1302,6 +1302,15 @@ static int gen9_init_perctx_bb(struct intel_engine_cs *ring,
>>   	struct drm_device *dev = ring->dev;
>>   	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
>>
>> +	/* WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken:skl,bxt */
>> +	if ((IS_SKYLAKE(dev) && (INTEL_REVID(dev) <= SKL_REVID_B0)) ||
>> +	    (IS_BROXTON(dev) && (INTEL_REVID(dev) == BXT_REVID_A0))) {
>> +		wa_ctx_emit(batch, MI_LOAD_REGISTER_IMM(1));
>> +		wa_ctx_emit(batch, GEN9_SLICE_COMMON_ECO_CHICKEN0);
>> +		wa_ctx_emit(batch, _MASKED_BIT_ENABLE(DISABLE_PIXEL_MASK_CAMMING));
>> +		wa_ctx_emit(batch, MI_NOOP);
>> +	}
>> +
>>   	/* WaDisableCtxRestoreArbitration:skl,bxt */
>>   	if ((IS_SKYLAKE(dev) && (INTEL_REVID(dev) <= SKL_REVID_D0)) ||
>>   	    (IS_BROXTON(dev) && (INTEL_REVID(dev) == BXT_REVID_A0)))
>> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> index af7c12e..66dde7f 100644
>> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
>> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
>> @@ -946,8 +946,11 @@ static int gen9_init_workarounds(struct intel_engine_cs *ring)
>>   		/* WaSetDisablePixMaskCammingAndRhwoInCommonSliceChicken:skl,bxt */
>>   		WA_SET_BIT_MASKED(GEN7_COMMON_SLICE_CHICKEN1,
>>   				  GEN9_RHWO_OPTIMIZATION_DISABLE);
>> -		WA_SET_BIT_MASKED(GEN9_SLICE_COMMON_ECO_CHICKEN0,
>> -				  DISABLE_PIXEL_MASK_CAMMING);
>> +		/*
>> +		 * WA also requires GEN9_SLICE_COMMON_ECO_CHICKEN0[14] to be set,
>> +		 * but that register is write only hence it is set
>> +		 * in per ctx batch buffer
>
> Why the need to move to per ctx bb? Why the write would not stick
> with this? Is the rationale that we get fails with the gem_workarounds?
>
> If so, perhaps we need a write_only marker for workaround list?
>
> -Mika

Surely it's the fact that it's a context-saved register that matters, 
rather than it being write-only (generally we treat masked registers as 
write-only anyway, since the masking means that you can set or clear a 
bit without having to read the other bits first).

Whereas AFAICS GEN7_COMMON_SLICE_CHICKEN1 is a global non-context 
register, so it can be set directly rather than having to be done in a 
batchbuffer.

.Dave.

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