On Thu, Dec 07, 2017 at 10:24:34PM +0000, Chris Wilson wrote:
> Currently on every submission, we recalculate the ELSP register offset
> for the engine, after chasing the pointers to find the iomem base. Since
> this is fixed for the lifetime of the driver record the offset in the
> execlists struct.
>
> In practice the difference is negligible, it just happens to remove 27
> bytes of eyesore pointer dancing from next to the hottest instruction
> (which is itself due to stalling for a cache miss) in perf profiles of
> the execlists_submission_tasklet().
>
> v2: Trim off one more elsp local.
>
> Signed-off-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
> Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
> Cc: Mika Kuoppala <mika.kuoppala@xxxxxxxxxxxxxxx>
> Reviewed-by: Michel Thierry <michel.thierry@xxxxxxxxx>
Reviewed-by: Rodrigo Vivi <rodrigo.vivi@xxxxxxxxx>
would this be useful somehow on error state?
> ---
> drivers/gpu/drm/i915/intel_lrc.c | 13 ++++++-------
> drivers/gpu/drm/i915/intel_ringbuffer.h | 5 +++++
> 2 files changed, 11 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_lrc.c b/drivers/gpu/drm/i915/intel_lrc.c
> index 2a8160f603ab..2e38fbfdf08f 100644
> --- a/drivers/gpu/drm/i915/intel_lrc.c
> +++ b/drivers/gpu/drm/i915/intel_lrc.c
> @@ -431,8 +431,6 @@ static inline void elsp_write(u64 desc, u32 __iomem *elsp)
> static void execlists_submit_ports(struct intel_engine_cs *engine)
> {
> struct execlist_port *port = engine->execlists.port;
> - u32 __iomem *elsp =
> - engine->i915->regs + i915_mmio_reg_offset(RING_ELSP(engine));
> unsigned int n;
>
> for (n = execlists_num_ports(&engine->execlists); n--; ) {
> @@ -458,7 +456,7 @@ static void execlists_submit_ports(struct intel_engine_cs *engine)
> desc = 0;
> }
>
> - elsp_write(desc, elsp);
> + elsp_write(desc, engine->execlists.elsp);
> }
> execlists_clear_active(&engine->execlists, EXECLISTS_ACTIVE_HWACK);
> }
> @@ -496,8 +494,6 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
> {
> struct intel_context *ce =
> &engine->i915->preempt_context->engine[engine->id];
> - u32 __iomem *elsp =
> - engine->i915->regs + i915_mmio_reg_offset(RING_ELSP(engine));
> unsigned int n;
>
> GEM_BUG_ON(engine->i915->preempt_context->hw_id != PREEMPT_ID);
> @@ -510,9 +506,9 @@ static void inject_preempt_context(struct intel_engine_cs *engine)
>
> GEM_TRACE("\n");
> for (n = execlists_num_ports(&engine->execlists); --n; )
> - elsp_write(0, elsp);
> + elsp_write(0, engine->execlists.elsp);
>
> - elsp_write(ce->lrc_desc, elsp);
> + elsp_write(ce->lrc_desc, engine->execlists.elsp);
> execlists_clear_active(&engine->execlists, EXECLISTS_ACTIVE_HWACK);
> }
>
> @@ -1509,6 +1505,9 @@ static int gen8_init_common_ring(struct intel_engine_cs *engine)
> execlists->csb_head = -1;
> execlists->active = 0;
>
> + execlists->elsp =
> + dev_priv->regs + i915_mmio_reg_offset(RING_ELSP(engine));
> +
> /* After a GPU reset, we may have requests to replay */
> if (execlists->first)
> tasklet_schedule(&execlists->tasklet);
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.h b/drivers/gpu/drm/i915/intel_ringbuffer.h
> index c68ab3ead83c..183165b9b3fb 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.h
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.h
> @@ -199,6 +199,11 @@ struct intel_engine_execlists {
> */
> bool no_priolist;
>
> + /**
> + * @elsp: the ExecList Submission Port register
> + */
> + u32 __iomem *elsp;
> +
> /**
> * @port: execlist port states
> *
> --
> 2.15.1
>
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