Re: [Intel-gfx] [PATCH 09/10] drm/i915/dg2: Enable Wa_14014475959 - RCS / CCS context exit

[John Harrison <john.c.harrison@intel.com>]

On 4/13/2022 12:27, Umesh Nerlige Ramappa wrote:
> From: Matthew Brost <matthew.brost@intel.com>
>
> There is bug in DG2 where if the CCS contexts switches out while the RCS
> is running it can cause memory corruption. To workaround this add an
> atomic to a memory address with a value 1 and semaphore wait to the same
> address for a value of 0. The GuC firmware is responsible for writing 0
> to the memory address when it is safe for the context to switch out.
>
> v2: Add atomic GPU instructions
> v3: Add w/a number (JohnH)
> v4: Set DW length to 9 atomic GPU instruction with inline data
> v5: Rebase (Umesh)
> v6: Split MI_ATOMIC definition into 2 (Daniele)
> v7: (Daniele)
> - For non-inline MI_ATOMIC, len should be 1
> - Make INLINE flag part of MI_ATOMIC_INLINE definition
>
> Signed-off-by: Matthew Brost <matthew.brost@intel.com>
Reviewed-by: John Harrison <John.C.Harrison@Intel.com>

> ---
>   drivers/gpu/drm/i915/gt/gen8_engine_cs.c      | 41 +++++++++++++++++++
>   drivers/gpu/drm/i915/gt/intel_engine_types.h  |  8 ++++
>   drivers/gpu/drm/i915/gt/intel_gpu_commands.h  |  7 ++++
>   drivers/gpu/drm/i915/gt/uc/intel_guc.c        |  4 ++
>   drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h   |  1 +
>   .../gpu/drm/i915/gt/uc/intel_guc_submission.c |  4 ++
>   6 files changed, 65 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> index 047b5a710149..9529c5455bc3 100644
> --- a/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> +++ b/drivers/gpu/drm/i915/gt/gen8_engine_cs.c
> @@ -583,6 +583,43 @@ static u32 *gen12_emit_preempt_busywait(struct i915_request *rq, u32 *cs)
>   	return cs;
>   }
>   
> +/* Wa_14014475959:dg2 */
> +#define CCS_SEMAPHORE_PPHWSP_OFFSET	0x540
> +static u32 ccs_semaphore_offset(struct i915_request *rq)
> +{
> +	return i915_ggtt_offset(rq->context->state) +
> +		(LRC_PPHWSP_PN * PAGE_SIZE) + CCS_SEMAPHORE_PPHWSP_OFFSET;
> +}
> +
> +/* Wa_14014475959:dg2 */
> +static u32 *ccs_emit_wa_busywait(struct i915_request *rq, u32 *cs)
> +{
> +	int i;
> +
> +	*cs++ = MI_ATOMIC_INLINE | MI_ATOMIC_GLOBAL_GTT | MI_ATOMIC_CS_STALL |
> +		MI_ATOMIC_MOVE;
> +	*cs++ = ccs_semaphore_offset(rq);
> +	*cs++ = 0;
> +	*cs++ = 1;
> +
> +	/*
> +	 * When MI_ATOMIC_INLINE_DATA set this command must be 11 DW + (1 NOP)
> +	 * to align. 4 DWs above + 8 filler DWs here.
> +	 */
> +	for (i = 0; i < 8; ++i)
> +		*cs++ = 0;
> +
> +	*cs++ = MI_SEMAPHORE_WAIT |
> +		MI_SEMAPHORE_GLOBAL_GTT |
> +		MI_SEMAPHORE_POLL |
> +		MI_SEMAPHORE_SAD_EQ_SDD;
> +	*cs++ = 0;
> +	*cs++ = ccs_semaphore_offset(rq);
> +	*cs++ = 0;
> +
> +	return cs;
> +}
> +
>   static __always_inline u32*
>   gen12_emit_fini_breadcrumb_tail(struct i915_request *rq, u32 *cs)
>   {
> @@ -593,6 +630,10 @@ gen12_emit_fini_breadcrumb_tail(struct i915_request *rq, u32 *cs)
>   	    !intel_uc_uses_guc_submission(&rq->engine->gt->uc))
>   		cs = gen12_emit_preempt_busywait(rq, cs);
>   
> +	/* Wa_14014475959:dg2 */
> +	if (intel_engine_uses_wa_hold_ccs_switchout(rq->engine))
> +		cs = ccs_emit_wa_busywait(rq, cs);
> +
>   	rq->tail = intel_ring_offset(rq, cs);
>   	assert_ring_tail_valid(rq->ring, rq->tail);
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> index eac20112709c..298f2cc7a879 100644
> --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h
> +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h
> @@ -529,6 +529,7 @@ struct intel_engine_cs {
>   #define I915_ENGINE_HAS_RCS_REG_STATE  BIT(9)
>   #define I915_ENGINE_HAS_EU_PRIORITY    BIT(10)
>   #define I915_ENGINE_FIRST_RENDER_COMPUTE BIT(11)
> +#define I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT BIT(12)
>   	unsigned int flags;
>   
>   	/*
> @@ -629,6 +630,13 @@ intel_engine_has_relative_mmio(const struct intel_engine_cs * const engine)
>   	return engine->flags & I915_ENGINE_HAS_RELATIVE_MMIO;
>   }
>   
> +/* Wa_14014475959:dg2 */
> +static inline bool
> +intel_engine_uses_wa_hold_ccs_switchout(struct intel_engine_cs *engine)
> +{
> +	return engine->flags & I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT;
> +}
> +
>   #define instdone_has_slice(dev_priv___, sseu___, slice___) \
>   	((GRAPHICS_VER(dev_priv___) == 7 ? 1 : ((sseu___)->slice_mask)) & BIT(slice___))
>   
> diff --git a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
> index 4243be030bc1..f3fe7d4c3234 100644
> --- a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
> +++ b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h
> @@ -134,6 +134,13 @@
>   #define   MI_MEM_VIRTUAL	(1 << 22) /* 945,g33,965 */
>   #define   MI_USE_GGTT		(1 << 22) /* g4x+ */
>   #define MI_STORE_DWORD_INDEX	MI_INSTR(0x21, 1)
> +#define MI_ATOMIC		MI_INSTR(0x2f, 1)
> +#define MI_ATOMIC_INLINE	(MI_INSTR(0x2f, 9) | MI_ATOMIC_INLINE_DATA)
> +#define   MI_ATOMIC_GLOBAL_GTT		(1 << 22)
> +#define   MI_ATOMIC_INLINE_DATA		(1 << 18)
> +#define   MI_ATOMIC_CS_STALL		(1 << 17)
> +#define	  MI_ATOMIC_MOVE		(0x4 << 8)
> +
>   /*
>    * Official intel docs are somewhat sloppy concerning MI_LOAD_REGISTER_IMM:
>    * - Always issue a MI_NOOP _before_ the MI_LOAD_REGISTER_IMM - otherwise hw
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc.c b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> index 830889349756..228070e31ef0 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc.c
> @@ -296,6 +296,10 @@ static u32 guc_ctl_wa_flags(struct intel_guc *guc)
>   	if (IS_DG2_GRAPHICS_STEP(gt->i915, G10, STEP_A0, STEP_B0))
>   		flags |= GUC_WA_GAM_CREDITS;
>   
> +	/* Wa_14014475959:dg2 */
> +	if (IS_DG2(gt->i915))
> +		flags |= GUC_WA_HOLD_CCS_SWITCHOUT;
> +
>   	/*
>   	 * Wa_14012197797:dg2_g10:a0,dg2_g11:a0
>   	 * Wa_22011391025:dg2_g10,dg2_g11,dg2_g12
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> index 126e67ea1619..e389a3a041a2 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_fwif.h
> @@ -102,6 +102,7 @@
>   #define   GUC_WA_DUAL_QUEUE		BIT(11)
>   #define   GUC_WA_RCS_RESET_BEFORE_RC6	BIT(13)
>   #define   GUC_WA_PRE_PARSER		BIT(14)
> +#define   GUC_WA_HOLD_CCS_SWITCHOUT	BIT(17)
>   #define   GUC_WA_POLLCS			BIT(18)
>   
>   #define GUC_CTL_FEATURE			2
> diff --git a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> index 38ba9f783312..1cb88e99b040 100644
> --- a/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> +++ b/drivers/gpu/drm/i915/gt/uc/intel_guc_submission.c
> @@ -3897,6 +3897,10 @@ static void guc_default_vfuncs(struct intel_engine_cs *engine)
>   	engine->flags |= I915_ENGINE_HAS_PREEMPTION;
>   	engine->flags |= I915_ENGINE_HAS_TIMESLICES;
>   
> +	/* Wa_14014475959:dg2 */
> +	if (IS_DG2(engine->i915) && engine->class == COMPUTE_CLASS)
> +		engine->flags |= I915_ENGINE_USES_WA_HOLD_CCS_SWITCHOUT;
> +
>   	/*
>   	 * TODO: GuC supports timeslicing and semaphores as well, but they're
>   	 * handled by the firmware so some minor tweaks are required before