On 20/01/2018 09:31, Chris Wilson wrote:
Now that we can read the CSB from the HWSP, we may avoid having to
perform mmio reads entirely and so forgo the rigmarole of the forcewake
dance.
Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
---
drivers/gpu/drm/i915/intel_lrc.c | 12 +++++++++---
1 file changed, 9 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
index ff25f209d0a5..7d2df72e68d3 100644
--- a/drivers/gpu/drm/i915/intel_lrc.c
+++ b/drivers/gpu/drm/i915/intel_lrc.c
@@ -778,6 +778,7 @@ static void execlists_submission_tasklet(unsigned long data)
struct intel_engine_execlists * const execlists = &engine->execlists;
struct execlist_port * const port = execlists->port;
struct drm_i915_private *dev_priv = engine->i915;
+ bool fw = false;
/* We can skip acquiring intel_runtime_pm_get() here as it was taken
* on our behalf by the request (see i915_gem_mark_busy()) and it will
@@ -788,8 +789,6 @@ static void execlists_submission_tasklet(unsigned long data)
*/
GEM_BUG_ON(!dev_priv->gt.awake);
- intel_uncore_forcewake_get(dev_priv, execlists->fw_domains);
-
/* Prefer doing test_and_clear_bit() as a two stage operation to avoid
* imposing the cost of a locked atomic transaction when submitting a
* new request (outside of the context-switch interrupt).
@@ -818,6 +817,12 @@ static void execlists_submission_tasklet(unsigned long data)
*/
__clear_bit(ENGINE_IRQ_EXECLIST, &engine->irq_posted);
if (unlikely(execlists->csb_head == -1)) { /* following a reset */
+ if (!fw) {
+ intel_uncore_forcewake_get(dev_priv,
+ execlists->fw_domains);
+ fw = true;
+ }
+
head = readl(dev_priv->regs + i915_mmio_reg_offset(RING_CONTEXT_STATUS_PTR(engine)));
tail = GEN8_CSB_WRITE_PTR(head);
head = GEN8_CSB_READ_PTR(head);
There's a GEM_TRACE which does a readl a line below, outside the if.
Then there's a writel down lower, under "if (head != execlists->csb_head)".
@@ -943,7 +948,8 @@ static void execlists_submission_tasklet(unsigned long data)
if (!execlists_is_active(execlists, EXECLISTS_ACTIVE_PREEMPT))
execlists_dequeue(engine);
- intel_uncore_forcewake_put(dev_priv, execlists->fw_domains);
+ if (fw)
+ intel_uncore_forcewake_put(dev_priv, execlists->fw_domains);
}
static void insert_request(struct intel_engine_cs *engine,
I had a similar patch, which also did some other tweaks, some of which I
think you recently also sent. So I support it in principle.
Regards,
Tvrtko
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