Re: [PATCH] drm/i915: Kick waiters on resetting legacy rings

[Mika Kuoppala <mika.kuoppala@linux.intel.com>]

Chris Wilson <chris@chris-wilson.co.uk> writes:

> This reapplies commit 39f3be162c46 ("drm/i915: Kick waiters on resetting
> legacy rings") after the improved gem_eio was run across all machines we
> found that gen3 and early gen4 still lost the immediate interrupt
> following reset, and the HWSTAM w/a applied to gen6+ is inadequate.
>
> Unlike the later gen, on gen3/4 the principle (and only tests to fail so
> far) are the wait vs reset test cases, whereas the reset stress case
> works fine (which was the predominantly failing case for gen6+). That is
> enough to suggest the underlying issue is sufficiently different to
> support the difference in HWSTAM efficacy.
>
> Testcase: igt/gem_eio/wait-10ms
> References: 39f3be162c46 ("drm/i915: Kick waiters on resetting legacy rings")
> References: a69ab52b0358 ("drm/i915: Remove extra waiter kick on legacy resets")
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Matthew Auld <matthew.auld@intel.com>
> Cc: Mika Kuoppala <mika.kuoppala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 2 ++
>  1 file changed, 2 insertions(+)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index b65cf7832b39..d40f55a8dc34 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -537,6 +537,8 @@ static int init_ring_common(struct intel_engine_cs *engine)
>  	if (INTEL_GEN(dev_priv) > 2)
>  		I915_WRITE_MODE(engine, _MASKED_BIT_DISABLE(STOP_RING));
>  
> +	/* Papering over lost _interrupts_ immediately following the restart */
> +	intel_engine_wakeup(engine);

We came, we toggled, we learned. Onwards!

Reviewed-by: Mika Kuoppala <mika.kuoppala@linux.intel.com>

>  out:
>  	intel_uncore_forcewake_put(dev_priv, FORCEWAKE_ALL);
>  
> -- 
> 2.18.0
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