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

Siluvery, Arun
2015-06-22T16:59:21Z

On 22/06/2015 17:21, Ville Syrjälä wrote:
> On Fri, Jun 19, 2015 at 06:37:15PM +0100, Arun Siluvery wrote:
>> In Per context w/a batch buffer,
>> WaRsRestoreWithPerCtxtBb
>>
>> This WA performs writes to scratch page so it must be valid, this check
>> is performed before initializing the batch with this WA.
>>
>> v2: This patches modifies definitions of MI_LOAD_REGISTER_MEM and
>> MI_LOAD_REGISTER_REG; Add GEN8 specific defines for these instructions
>> so as to not break any future users of existing definitions (Michel)
>>
>> v3: Length defined in current definitions of LRM, LRR instructions was specified
>> as 0. It seems it is common convention for instructions whose length vary between
>> platforms. This is not an issue so far because they are not used anywhere except
>> command parser; now that we use in this patch update them with correct length
>> and also move them out of command parser placeholder to appropriate place.
>> remove unnecessary padding and follow the WA programming sequence exactly
>> as mentioned in spec which is essential for this WA (Dave).
>>
>> 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 | 29 +++++++++++++++++++--
>> drivers/gpu/drm/i915/intel_lrc.c | 54 ++++++++++++++++++++++++++++++++++++++++
>> 2 files changed, 81 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h
>> index 7637e64..208620d 100644
>> --- a/drivers/gpu/drm/i915/i915_reg.h
>> +++ b/drivers/gpu/drm/i915/i915_reg.h
>> @@ -347,6 +347,31 @@
>> #define MI_INVALIDATE_BSD (1<<7)
>> #define MI_FLUSH_DW_USE_GTT (1<<2)
>> #define MI_FLUSH_DW_USE_PPGTT (0<<2)
>> +#define MI_LOAD_REGISTER_MEM MI_INSTR(0x29, 1)
>> +#define MI_LOAD_REGISTER_MEM_GEN8 MI_INSTR(0x29, 2)
>> +#define MI_LRM_USE_GLOBAL_GTT (1<<22)
>> +#define MI_LRM_ASYNC_MODE_ENABLE (1<<21)
>> +#define MI_LOAD_REGISTER_REG MI_INSTR(0x2A, 1)
>> +#define MI_ATOMIC(len) MI_INSTR(0x2F, (len-2))
>> +#define MI_ATOMIC_MEMORY_TYPE_GGTT (1<<22)
>> +#define MI_ATOMIC_INLINE_DATA (1<<18)
>> +#define MI_ATOMIC_CS_STALL (1<<17)
>> +#define MI_ATOMIC_RETURN_DATA_CTL (1<<16)
>> +#define MI_ATOMIC_OP_MASK(op) ((op) << 8)
>> +#define MI_ATOMIC_AND MI_ATOMIC_OP_MASK(0x01)
>> +#define MI_ATOMIC_OR MI_ATOMIC_OP_MASK(0x02)
>> +#define MI_ATOMIC_XOR MI_ATOMIC_OP_MASK(0x03)
>> +#define MI_ATOMIC_MOVE MI_ATOMIC_OP_MASK(0x04)
>> +#define MI_ATOMIC_INC MI_ATOMIC_OP_MASK(0x05)
>> +#define MI_ATOMIC_DEC MI_ATOMIC_OP_MASK(0x06)
>> +#define MI_ATOMIC_ADD MI_ATOMIC_OP_MASK(0x07)
>> +#define MI_ATOMIC_SUB MI_ATOMIC_OP_MASK(0x08)
>> +#define MI_ATOMIC_RSUB MI_ATOMIC_OP_MASK(0x09)
>> +#define MI_ATOMIC_IMAX MI_ATOMIC_OP_MASK(0x0A)
>> +#define MI_ATOMIC_IMIN MI_ATOMIC_OP_MASK(0x0B)
>> +#define MI_ATOMIC_UMAX MI_ATOMIC_OP_MASK(0x0C)
>> +#define MI_ATOMIC_UMIN MI_ATOMIC_OP_MASK(0x0D)
>> +
>> #define MI_BATCH_BUFFER MI_INSTR(0x30, 1)
>> #define MI_BATCH_NON_SECURE (1)
>> /* for snb/ivb/vlv this also means "batch in ppgtt" when ppgtt is enabled. */
>> @@ -451,8 +476,6 @@
>> #define MI_CLFLUSH MI_INSTR(0x27, 0)
>> #define MI_REPORT_PERF_COUNT MI_INSTR(0x28, 0)
>> #define MI_REPORT_PERF_COUNT_GGTT (1<<0)
>> -#define MI_LOAD_REGISTER_MEM MI_INSTR(0x29, 0)
>> -#define MI_LOAD_REGISTER_REG MI_INSTR(0x2A, 0)
>> #define MI_RS_STORE_DATA_IMM MI_INSTR(0x2B, 0)
>> #define MI_LOAD_URB_MEM MI_INSTR(0x2C, 0)
>> #define MI_STORE_URB_MEM MI_INSTR(0x2D, 0)
>> @@ -1799,6 +1822,8 @@ enum skl_disp_power_wells {
>> #define GEN8_RC_SEMA_IDLE_MSG_DISABLE (1 << 12)
>> #define GEN8_FF_DOP_CLOCK_GATE_DISABLE (1<<10)
>>
>> +#define GEN8_RS_PREEMPT_STATUS 0x215C
>> +
>> /* Fuse readout registers for GT */
>> #define CHV_FUSE_GT (VLV_DISPLAY_BASE + 0x2168)
>> #define CHV_FGT_DISABLE_SS0 (1 << 10)
>> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
>> index 664455c..28198c4 100644
>> --- a/drivers/gpu/drm/i915/intel_lrc.c
>> +++ b/drivers/gpu/drm/i915/intel_lrc.c
>> @@ -1215,11 +1215,65 @@ static int gen8_init_perctx_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);
>>
>> + /* Actual scratch location is at 128 bytes offset */
>> + scratch_addr = ring->scratch.gtt_offset + 2*CACHELINE_BYTES;
>> + scratch_addr |= PIPE_CONTROL_GLOBAL_GTT;
>> +
>> /* WaDisableCtxRestoreArbitration:bdw,chv */
>> wa_ctx_emit(batch, MI_ARB_ON_OFF | MI_ARB_ENABLE);
>>
>> + /*
>> + * As per Bspec, to workaround a known HW issue, SW must perform the
>> + * below programming sequence prior to programming MI_BATCH_BUFFER_END.
>> + *
>> + * This is only applicable for Gen8.
>> + */
>> +
>> + /* WaRsRestoreWithPerCtxtBb:bdw,chv */
>
> This w/a doesn't seem to be needed for CHV. Also BDW seems to have
> gained a chicken bit in H0 (FF_SLICE_CS_CHICKEN3[5]) that supposedly
> means we shouldn't need this w/a on BDW either.
>
looks like this chicken bit is applying this WA, if this is working as
expected then we can ignore this patch, I will try to get some
confirmation on this.

regards
Arun

>> + wa_ctx_emit(batch, MI_LOAD_REGISTER_IMM(1));
>> + wa_ctx_emit(batch, INSTPM);
>> + wa_ctx_emit(batch, _MASKED_BIT_DISABLE(INSTPM_FORCE_ORDERING));
>> +
>> + wa_ctx_emit(batch, (MI_ATOMIC(5) |
>> + MI_ATOMIC_MEMORY_TYPE_GGTT |
>> + MI_ATOMIC_INLINE_DATA |
>> + MI_ATOMIC_CS_STALL |
>> + MI_ATOMIC_RETURN_DATA_CTL |
>> + MI_ATOMIC_MOVE));
>> + wa_ctx_emit(batch, scratch_addr);
>> + wa_ctx_emit(batch, 0);
>> + wa_ctx_emit(batch, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));
>> + wa_ctx_emit(batch, _MASKED_BIT_ENABLE(INSTPM_FORCE_ORDERING));
>> +
>> + /*
>> + * BSpec says MI_LOAD_REGISTER_MEM, MI_LOAD_REGISTER_REG and
>> + * MI_BATCH_BUFFER_END instructions in this sequence need to be
>> + * in the same cacheline. To satisfy this case even if more WA are
>> + * added in future, pad current cacheline and start remaining sequence
>> + * in new cacheline.
>> + */
>> + while (index % CACHELINE_DWORDS)
>> + wa_ctx_emit(batch, MI_NOOP);
>> +
>> + wa_ctx_emit(batch, (MI_LOAD_REGISTER_MEM_GEN8 |
>> + MI_LRM_USE_GLOBAL_GTT |
>> + MI_LRM_ASYNC_MODE_ENABLE));
>> + wa_ctx_emit(batch, INSTPM);
>> + wa_ctx_emit(batch, scratch_addr);
>> + wa_ctx_emit(batch, 0);
>> +
>> + /*
>> + * BSpec says there should not be any commands programmed
>> + * between MI_LOAD_REGISTER_REG and MI_BATCH_BUFFER_END so
>> + * do not add any new commands
>> + */
>> + wa_ctx_emit(batch, MI_LOAD_REGISTER_REG);
>> + wa_ctx_emit(batch, GEN8_RS_PREEMPT_STATUS);
>> + wa_ctx_emit(batch, GEN8_RS_PREEMPT_STATUS);
>> +
>> wa_ctx_emit(batch, MI_BATCH_BUFFER_END);
>>
>> return wa_ctx_end(wa_ctx, *offset = index, 1);
>> --
>> 2.3.0
>>
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