On 2018-03-30 20:23, Daniele Ceraolo Spurio wrote:
The engine->flag which Chris introduced is now used to set I915_SCHEDULER_CAP_PREEMPTION.On 27/03/18 16:27, Chris Wilson wrote:Quoting Tomasz Lis (2018-03-27 16:17:59)The patch adds support of preempt-to-idle requesting by setting a proper bit within Execlist Control Register, and receiving preemption result fromContext Status Buffer.Preemption in previous gens required a special batch buffer to be executed, so the Command Streamer never preempted to idle directly. In Icelake it ispossible, as there is a hardware mechanism to inform the kernel about status of the preemption request.This patch does not cover using the new preemption mechanism when GuC isactive. Bspec: 18922 Signed-off-by: Tomasz Lis <tomasz....@intel.com> --- drivers/gpu/drm/i915/i915_drv.h | 2 ++ drivers/gpu/drm/i915/i915_pci.c | 3 ++- drivers/gpu/drm/i915/intel_device_info.h | 1 +drivers/gpu/drm/i915/intel_lrc.c | 45 +++++++++++++++++++++++++++-----drivers/gpu/drm/i915/intel_lrc.h | 1 + 5 files changed, 45 insertions(+), 7 deletions(-)diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.hindex 800230b..c32580b 100644 --- a/drivers/gpu/drm/i915/i915_drv.h +++ b/drivers/gpu/drm/i915/i915_drv.h@@ -2514,6 +2514,8 @@ intel_info(const struct drm_i915_private *dev_priv)((dev_priv)->info.has_logical_ring_elsq) #define HAS_LOGICAL_RING_PREEMPTION(dev_priv) \ ((dev_priv)->info.has_logical_ring_preemption) +#define HAS_HW_PREEMPT_TO_IDLE(dev_priv) \ + ((dev_priv)->info.has_hw_preempt_to_idle) #define HAS_EXECLISTS(dev_priv) HAS_LOGICAL_RING_CONTEXTS(dev_priv)diff --git a/drivers/gpu/drm/i915/i915_pci.c b/drivers/gpu/drm/i915/i915_pci.cindex 4364922..66b6700 100644 --- a/drivers/gpu/drm/i915/i915_pci.c +++ b/drivers/gpu/drm/i915/i915_pci.c@@ -595,7 +595,8 @@ static const struct intel_device_info intel_cannonlake_info = {GEN(11), \ .ddb_size = 2048, \ .has_csr = 0, \ - .has_logical_ring_elsq = 1 + .has_logical_ring_elsq = 1, \ + .has_hw_preempt_to_idle = 1 static const struct intel_device_info intel_icelake_11_info = { GEN11_FEATURES,diff --git a/drivers/gpu/drm/i915/intel_device_info.h b/drivers/gpu/drm/i915/intel_device_info.hindex 933e316..4eb97b5 100644 --- a/drivers/gpu/drm/i915/intel_device_info.h +++ b/drivers/gpu/drm/i915/intel_device_info.h @@ -98,6 +98,7 @@ enum intel_platform { func(has_logical_ring_contexts); \ func(has_logical_ring_elsq); \ func(has_logical_ring_preemption); \ + func(has_hw_preempt_to_idle); \ func(has_overlay); \ func(has_pooled_eu); \ func(has_psr); \diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.cindex ba7f783..1a22de4 100644 --- a/drivers/gpu/drm/i915/intel_lrc.c +++ b/drivers/gpu/drm/i915/intel_lrc.c @@ -153,6 +153,7 @@ #define GEN8_CTX_STATUS_ACTIVE_IDLE (1 << 3) #define GEN8_CTX_STATUS_COMPLETE (1 << 4) #define GEN8_CTX_STATUS_LITE_RESTORE (1 << 15) +#define GEN11_CTX_STATUS_PREEMPT_IDLE (1 << 29) #define GEN8_CTX_STATUS_COMPLETED_MASK \ (GEN8_CTX_STATUS_COMPLETE | GEN8_CTX_STATUS_PREEMPTED)@@ -183,7 +184,9 @@ static inline bool need_preempt(const struct intel_engine_cs *engine,const struct i915_request *last, int prio) {- return engine->i915->preempt_context && prio > max(rq_prio(last), 0);+ return (engine->i915->preempt_context || + HAS_HW_PREEMPT_TO_IDLE(engine->i915)) &&Well, you haven't actually disabled allocating the preempt_context so... But at any rate, making this an engine->flag would eliminate one pointer dance.Can't we re-use I915_SCHEDULER_CAP_PREEMPTION in engine->i915->caps.scheduler? That btw like here to be set if i915->preempt_context || HAS_HW_PREEMPT_TO_IDLE(i915)
Wow. I have no idea how I was able to test this patch and not trigger this. You are right.+ prio > max(rq_prio(last), 0); } /**@@ -535,6 +538,25 @@ static void inject_preempt_context(struct intel_engine_cs *engine) execlists_set_active(&engine->execlists, EXECLISTS_ACTIVE_PREEMPT);} +static void gen11_preempt_to_idle(struct intel_engine_cs *engine) +{ + struct intel_engine_execlists *execlists = &engine->execlists; + + GEM_TRACE("%s\n", engine->name); + + /* + * hardware which HAS_HW_PREEMPT_TO_IDLE(), always also + * HAS_LOGICAL_RING_ELSQ(), so we can assume ctrl_reg is set + */ + GEM_BUG_ON(execlists->ctrl_reg != NULL);Shouldn't this check be the other way around?
+ + /* trigger preemption to idle */ + writel(EL_CTRL_PREEMPT_TO_IDLE, execlists->ctrl_reg);Future plans? Because just inserting the branch into the setter of inject_preempt_context() resolves a lot of conflicts with other work.@@ -962,10 +987,13 @@ static void execlists_submission_tasklet(unsigned long data)status, buf[2*head + 1], execlists->active); - if (status & (GEN8_CTX_STATUS_IDLE_ACTIVE | - GEN8_CTX_STATUS_PREEMPTED))+ /* Check if switched to active or preempted to active */+ if ((status & (GEN8_CTX_STATUS_IDLE_ACTIVE | + GEN8_CTX_STATUS_PREEMPTED)) && + !(status & GEN11_CTX_STATUS_PREEMPT_IDLE))Setting HWACK here is harmless as it gets cleared again. Unless, there is some oddity in the code flow.There is actually some oddity, but it is more on the HW side. A preempt to idle can potentially land on an already idle HW, in which case GEN8_CTX_STATUS_ACTIVE_IDLE is not set and GEN8_CTX_STATUS_IDLE_ACTIVE is set instead. In this case without this check on GEN11_CTX_STATUS_PREEMPT_IDLE we would set the HWACK here but we wouldn't call the clear below. Not sure if we end up clearing the flag elsewhere, but that doesn't look too nice IMHO.BTW, the relevant CSB bits coming out in the 2 preempt to idle cases are as follows:preempt active HW:GEN11_CTX_STATUS_PREEMPT_IDLE | GEN8_CTX_STATUS_ACTIVE_IDLE | GEN8_CTX_STATUS_PREEMPTEDPreempt idle HW: GEN11_CTX_STATUS_PREEMPT_IDLE | GEN8_CTX_STATUS_IDLE_ACTIVE Daniele
Thanks Daniele, this makes things a lot clearer.Considering also HWACK description from Chris, I will add a condition to execlists_clear_active() below instead of here.
-Tomasz
execlists_set_active(execlists, EXECLISTS_ACTIVE_HWACK); + if (status & GEN8_CTX_STATUS_ACTIVE_IDLE) execlists_clear_active(execlists, EXECLISTS_ACTIVE_HWACK);@@ -976,8 +1004,13 @@ static void execlists_submission_tasklet(unsigned long data) /* We should never get a COMPLETED | IDLE_ACTIVE! */ GEM_BUG_ON(status & GEN8_CTX_STATUS_IDLE_ACTIVE);- if (status & GEN8_CTX_STATUS_COMPLETE &&- buf[2*head + 1] == execlists->preempt_complete_status) {+ /*+ * Check if preempted to real idle, either directly or + * the preemptive context already finished executing+ */ + if ((status & GEN11_CTX_STATUS_PREEMPT_IDLE) || + (status & GEN8_CTX_STATUS_COMPLETE &&+ buf[2*head + 1] == execlists->preempt_complete_status)) { GEM_TRACE("%s preempt-idle\n", engine->name);Hmm. I was hoping that we would be able to engineer a single check to cover all sins. Might have been overly optimistic, but I can dream. -Chris _______________________________________________ Intel-gfx mailing list Intel-gfx@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gfx
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