Re: [Intel-gfx] [RFC PATCH 33/97] drm/i915: Engine relative MMIO

On 06/05/2021 20:13, Matthew Brost wrote:

From: John Harrison John.C.Harrison@Intel.com

With virtual engines, it is no longer possible to know which specific physical engine a given request will be executed on at the time that request is generated. This means that the request itself must be engine agnostic - any direct register writes must be relative to the engine and not absolute addresses.

The LRI command has support for engine relative addressing. However, the mechanism is not transparent to the driver. The scheme for Gen11 (MI_LRI_ADD_CS_MMIO_START) requires the LRI address to have no absolute engine base component. The hardware then adds on the correct engine offset at execution time.

Due to the non-trivial and differing schemes on different hardware, it is not possible to simply update the code that creates the LRI commands to set a remap flag and let the hardware get on with it. Instead, this patch adds function wrappers for generating the LRI command itself and then for constructing the correct address to use with the LRI.

Bspec: 45606 Signed-off-by: John Harrison John.C.Harrison@Intel.com Signed-off-by: Matthew Brost matthew.brost@intel.com CC: Rodrigo Vivi rodrigo.vivi@intel.com CC: Tvrtko Ursulin tvrtko.ursulin@intel.com CC: Chris P Wilson chris.p.wilson@intel.com CC: Daniele Ceraolo Spurio daniele.ceraolospurio@intel.com

---

drivers/gpu/drm/i915/gem/i915_gem_context.c | 7 +++--- drivers/gpu/drm/i915/gt/intel_engine_cs.c | 25 ++++++++++++++++++++ drivers/gpu/drm/i915/gt/intel_engine_types.h | 3 +++ drivers/gpu/drm/i915/gt/intel_gpu_commands.h | 5 ++++ drivers/gpu/drm/i915/i915_perf.c | 6 +++++ 5 files changed, 43 insertions(+), 3 deletions(-)

diff --git a/drivers/gpu/drm/i915/gem/i915_gem_context.c b/drivers/gpu/drm/i915/gem/i915_gem_context.c index 188dee13e017..993faa213b41 100644 --- a/drivers/gpu/drm/i915/gem/i915_gem_context.c +++ b/drivers/gpu/drm/i915/gem/i915_gem_context.c @@ -1211,7 +1211,7 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data) { struct i915_address_space *vm = rq->context->vm; struct intel_engine_cs *engine = rq->engine;

• u32 base = engine->mmio_base;

• u32 base = engine->lri_mmio_base; u32 *cs; int i;

@@ -1223,7 +1223,7 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data) if (IS_ERR(cs)) return PTR_ERR(cs);

• *cs++ = MI_LOAD_REGISTER_IMM(2);
  

• *cs++ = MI_LOAD_REGISTER_IMM(2) | engine->lri_cmd_mode;
  

Would a helper like MI_LOAD_REGISTER_IMM_REL(engine, n) look better?

*cs++ = i915_mmio_reg_offset(GEN8_RING_PDP_UDW(base, 0));
*cs++ = upper_32_bits(pd_daddr);

@@ -1245,7 +1245,8 @@ static int emit_ppgtt_update(struct i915_request *rq, void *data) if (IS_ERR(cs)) return PTR_ERR(cs);

• *cs++ = MI_LOAD_REGISTER_IMM(2 * GEN8_3LVL_PDPES) | MI_LRI_FORCE_POSTED;
  

• *cs++ = MI_LOAD_REGISTER_IMM(2 * GEN8_3LVL_PDPES) |
  

• 	MI_LRI_FORCE_POSTED | engine->lri_cmd_mode;
  

  for (i = GEN8_3LVL_PDPES; i--; ) { const dma_addr_t pd_daddr = i915_page_dir_dma_addr(ppgtt, i);

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_cs.c b/drivers/gpu/drm/i915/gt/intel_engine_cs.c index ec82a7ec0c8d..c88b792c1ab5 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_cs.c +++ b/drivers/gpu/drm/i915/gt/intel_engine_cs.c @@ -16,6 +16,7 @@ #include "intel_engine_pm.h" #include "intel_engine_user.h" #include "intel_execlists_submission.h" +#include "intel_gpu_commands.h" #include "intel_gt.h" #include "intel_gt_requests.h" #include "intel_gt_pm.h" @@ -223,6 +224,28 @@ static u32 __engine_mmio_base(struct drm_i915_private *i915, return bases[i].base; }

+static bool i915_engine_has_relative_lri(const struct intel_engine_cs *engine) +{

• if (INTEL_GEN(engine->i915) < 11)

• return false;
  

• if (engine->class == COPY_ENGINE_CLASS)

• return false;
  

• return true;

+}

+static void lri_init(struct intel_engine_cs *engine) +{

• if (i915_engine_has_relative_lri(engine)) {

• engine->lri_cmd_mode = MI_LRI_LRM_CS_MMIO;
  

• engine->lri_mmio_base = 0;
  

• } else {

• engine->lri_cmd_mode = 0;
  

• engine->lri_mmio_base = engine->mmio_base;
  

• }

+}

• static void __sprint_engine_name(struct intel_engine_cs *engine) { /*

@@ -327,6 +350,8 @@ static int intel_engine_setup(struct intel_gt *gt, enum intel_engine_id id) if (engine->context_size) DRIVER_CAPS(i915)->has_logical_contexts = true;

• lri_init(engine);
• ewma__engine_latency_init(&engine->latency); seqcount_init(&engine->stats.lock);

diff --git a/drivers/gpu/drm/i915/gt/intel_engine_types.h b/drivers/gpu/drm/i915/gt/intel_engine_types.h index 93aa22680db0..86302e6d86b2 100644 --- a/drivers/gpu/drm/i915/gt/intel_engine_types.h +++ b/drivers/gpu/drm/i915/gt/intel_engine_types.h @@ -281,6 +281,9 @@ struct intel_engine_cs { u32 context_size; u32 mmio_base;

• u32 lri_mmio_base;
• u32 lri_cmd_mode;
• /*
  • Some w/a require forcewake to be held (which prevents RC6) while
  • a particular engine is active. If so, we set fw_domain to which

diff --git a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h index 14e2ffb6c0e5..887d59897bc2 100644 --- a/drivers/gpu/drm/i915/gt/intel_gpu_commands.h +++ b/drivers/gpu/drm/i915/gt/intel_gpu_commands.h @@ -134,6 +134,11 @@

• simply ignores the register load under certain conditions.
• • One can actually load arbitrary many arbitrary registers: Simply issue x
• address/value pairs. Don't overdue it, though, x <= 2^4 must hold!

• • • Newer hardware supports engine relative addressing but older hardware does
• • not. This is required for hw engine load balancing. Hence the MI_LRI
• • instruction itself is prefixed with '__' and should only be used on
• • legacy hardware code paths. Generic code must always use the MI_LRI
• • and i915_get_lri_reg() helper functions instead.

Stale comment.

*/ #define MI_LOAD_REGISTER_IMM(x) MI_INSTR(0x22, 2*(x)-1) /* Gen11+. addr = base + (ctx_restore ? offset & GENMASK(12,2) : offset) */ diff --git a/drivers/gpu/drm/i915/i915_perf.c b/drivers/gpu/drm/i915/i915_perf.c index 66f1f25119b5..b9cc3f0a616f 100644 --- a/drivers/gpu/drm/i915/i915_perf.c +++ b/drivers/gpu/drm/i915/i915_perf.c @@ -2118,6 +2118,11 @@ gen8_update_reg_state_unlocked(const struct intel_context *ce, u32 *reg_state = ce->lrc_reg_state; int i;

• /*

• * NB: The LRI instruction is generated by the hardware.
  

• * Should we read it in and assert that the offset flag is set?
  

• */
  

• reg_state[ctx_oactxctrl + 1] = (stream->period_exponent << GEN8_OA_TIMER_PERIOD_SHIFT) | (stream->periodic ? GEN8_OA_TIMER_ENABLE : 0) |

@@ -2174,6 +2179,7 @@ gen8_load_flex(struct i915_request *rq,

*cs++ = MI_LOAD_REGISTER_IMM(count); do {

• /* FIXME: Is this table LRI remap/offset friendly? */
  

  *cs++ = i915_mmio_reg_offset(flex->reg); *cs++ = flex->value; } while (flex++, --count);

NB and FIXME would ideally be resolved before merging.

Regards,

Tvrtko