Re: [PATCH 1/2] drm/i915: Unmask user interrupts writes into HWSP on snb/ivb/vlv/hsw

From: Mika Kuoppala <mika.kuoppala@linux.intel.com>
To: Chris Wilson <chris@chris-wilson.co.uk>, intel-gfx@lists.freedesktop.org
Subject: Re: [PATCH 1/2] drm/i915: Unmask user interrupts writes into HWSP on snb/ivb/vlv/hsw
Date: Wed, 08 Aug 2018 11:35:51 +0300	[thread overview]
Message-ID: <87tvo545nc.fsf@gaia.fi.intel.com> (raw)
In-Reply-To: <20180807222358.16366-1-chris@chris-wilson.co.uk>

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

> An oddity occurs on Sandybridge, Ivybridge and Haswell (and presumably
> Valleyview) in that for the period following the GPU restart after a
> reset, there are no GT interrupts received. From Ville's notes, bit 0 in
> the HWSTAM corresponds to the render interrupt, and if we unmask it we
> do see immediate resumption of GT interrupt delivery (via the master irq
> handler) after the reset.
>
> Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107500
> Fixes: c5498089463b ("drm/i915: Mask everything in ring HWSTAM on gen6+ in ringbuffer mode")
> References: d420a50c21ef ("drm/i915: Clean up the HWSTAM mess")
> Testcase: igt/gem_eio/reset-stress
> Signed-off-by: Chris Wilson <chris@chris-wilson.co.uk>
> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com>
> ---
>  drivers/gpu/drm/i915/intel_ringbuffer.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_ringbuffer.c b/drivers/gpu/drm/i915/intel_ringbuffer.c
> index 8003cef767ba..9b526b0f755a 100644
> --- a/drivers/gpu/drm/i915/intel_ringbuffer.c
> +++ b/drivers/gpu/drm/i915/intel_ringbuffer.c
> @@ -388,7 +388,7 @@ static void intel_ring_setup_status_page(struct intel_engine_cs *engine)
>  	}
>  
>  	if (INTEL_GEN(dev_priv) >= 6)
> -		I915_WRITE(RING_HWSTAM(engine->mmio_base), 0xffffffff);
> +		I915_WRITE(RING_HWSTAM(engine->mmio_base), 0xfffffffe);

Yeah bit 0 is MI_USER_INTERRUPT on render. And execlists keeps all masked.

There are bits for other engines too so add more paranoia?
-Mika
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