On 2018-03-28 01:27, 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 from
Context 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 is
possible, 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 is
active.
Bspec: 18922
Signed-off-by: Tomasz Lis <tomasz.lis@xxxxxxxxx>
---
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.h
index 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.c
index 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.h
index 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.c
index 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...
Yes.. I had mixed feelings about changing needs_preempt_context() now,
as that would mean adding a temporary condition on GuC until the GuC
preemption is merged.
I will add the conditions and disable the allocation in v2 of the patch.
But at any rate, making this an engine->flag would eliminate one pointer
dance.
Could be an interesting idea for a separate patch.
+ 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);
+
+ /* 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.
My arguments for separate function are:
- better code readability
- keeping the symmetry between execlist and GuC flow - GuC preemption
patches will introduce separate function as well
- only 4 lines of the function would be common
- the name inject_preempt_context() wouldn't match the new purpose, so
renaming would be needed
- reduced self-documenting code due to two separate preempt methods not
having distinct names
That's all, I don't have any future plans for it. If you want me to
merge the two, let me know.
@@ -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.
I will check if lack of the change affects test results.
Personally, I would keep this change, even if only for allowing simple
definition of what HWACK flag means.
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
I don't see any way to do that, besides creating separate function for
gen11.
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