Re: [PATCH v6 5/6] drm/i915/gen8: Add WaClearSlmSpaceAtContextSwitch workaround

From: "Siluvery, Arun" <arun.siluvery@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>,
	intel-gfx@lists.freedesktop.org,
	Dave Gordon <david.s.gordon@intel.com>,
	Rafael Barbalho <rafael.barbalho@intel.com>
Subject: Re: [PATCH v6 5/6] drm/i915/gen8: Add WaClearSlmSpaceAtContextSwitch workaround
Date: Mon, 22 Jun 2015 12:29:05 +0100	[thread overview]
Message-ID: <5587F181.6070003@linux.intel.com> (raw)
In-Reply-To: <20150619180959.GE29508@nuc-i3427.alporthouse.com>

On 19/06/2015 19:09, Chris Wilson wrote:
> On Fri, Jun 19, 2015 at 06:37:14PM +0100, Arun Siluvery wrote:
>> In Indirect context w/a batch buffer,
>> WaClearSlmSpaceAtContextSwitch
>>
>> This WA performs writes to scratch page so it must be valid, this check
>> is performed before initializing the batch with this WA.
>>
>> v2: s/PIPE_CONTROL_FLUSH_RO_CACHES/PIPE_CONTROL_FLUSH_L3 (Ville)
>>
>> Cc: Chris Wilson <chris@chris-wilson.co.uk>
>> Cc: Dave Gordon <david.s.gordon@intel.com>
>> Signed-off-by: Rafael Barbalho <rafael.barbalho@intel.com>
>> Signed-off-by: Arun Siluvery <arun.siluvery@linux.intel.com>
>> ---
>>   drivers/gpu/drm/i915/i915_reg.h  |  1 +
>>   drivers/gpu/drm/i915/intel_lrc.c | 16 ++++++++++++++++
>>   2 files changed, 17 insertions(+)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
>> index d14ad20..7637e64 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -410,6 +410,7 @@
>>   #define   DISPLAY_PLANE_A           (0<<20)
>>   #define   DISPLAY_PLANE_B           (1<<20)
>>   #define GFX_OP_PIPE_CONTROL(len)	((0x3<<29)|(0x3<<27)|(0x2<<24)|(len-2))
>> +#define   PIPE_CONTROL_FLUSH_L3				(1<<27)
>>   #define   PIPE_CONTROL_GLOBAL_GTT_IVB			(1<<24) /* gen7+ */
>>   #define   PIPE_CONTROL_MMIO_WRITE			(1<<23)
>>   #define   PIPE_CONTROL_STORE_DATA_INDEX			(1<<21)
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index 3e7aaa9..664455c 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -1137,6 +1137,7 @@ static int gen8_init_indirectctx_bb(struct intel_engine_cs *ring,
>>   				    uint32_t *const batch,
>>   				    uint32_t *offset)
>>   {
>> +	uint32_t scratch_addr;
>>   	uint32_t index = wa_ctx_start(wa_ctx, *offset, CACHELINE_DWORDS);
>>
>>   	/* WaDisableCtxRestoreArbitration:bdw,chv */
>> @@ -1165,6 +1166,21 @@ static int gen8_init_indirectctx_bb(struct intel_engine_cs *ring,
>>   		wa_ctx_emit(batch, l3sqc4_flush & ~GEN8_LQSC_FLUSH_COHERENT_LINES);
>>   	}
>>
>> +	/* WaClearSlmSpaceAtContextSwitch:bdw,chv */
>> +	/* Actual scratch location is at 128 bytes offset */
>> +	scratch_addr = ring->scratch.gtt_offset + 2*CACHELINE_BYTES;
>> +	scratch_addr |= PIPE_CONTROL_GLOBAL_GTT;
>
> I thought this bit was now mbz - that's how we treat it elsewhere e.g.
> gen8_emit_flush_render, and that the address has to be naturally aligned
> for the target write. (Similar bit in patch 6 fwiw.)
you are correct, this bit is mbz.

Daniel, could you please remove this line when applying patches?
sorry for additional work.

 >> +	scratch_addr |= PIPE_CONTROL_GLOBAL_GTT;

regards
Arun

> -Chris
>

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