Quoting Tvrtko Ursulin (2018-01-22 09:50:57)
>
> 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.
Yeah, I didn't care too much about it. Maybe if we include fw into the
trace so we know whether to believe it or not.
-Chris
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