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

Chris Wilson
2015-06-19T18:10:05Z

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.)
-Chris

--
Chris Wilson, Intel Open Source Technology Centre