Re: [PATCH 12/15] drm/i915: Interrupt routing for GuC submission

[Dave Gordon <david.s.gordon@intel.com>]

On 17/06/15 13:41, Daniel Vetter wrote:
> On Wed, Jun 17, 2015 at 02:22:19PM +0200, Daniel Vetter wrote:
>> On Wed, Jun 17, 2015 at 09:20:44AM +0100, Dave Gordon wrote:
>>> On 16/06/15 10:24, Chris Wilson wrote:
>>>> On Mon, Jun 15, 2015 at 07:36:30PM +0100, Dave Gordon wrote:
>>>>> +static void direct_interrupts_to_guc(struct drm_i915_private *dev_priv)
>>>>> +{
>>>>> +	struct intel_engine_cs *ring;
>>>>> +	int i, irqs;
>>>>> +
>>>>> +	/* tell all command streamers to forward interrupts and vblank to GuC */
>>>>> +	irqs = _MASKED_FIELD(GFX_FORWARD_VBLANK_MASK, GFX_FORWARD_VBLANK_ALWAYS);
>>>>> +	irqs |= _MASKED_BIT_ENABLE(GFX_INTERRUPT_STEERING);
>>>>> +	for_each_ring(ring, dev_priv, i)
>>>>> +		I915_WRITE(RING_MODE_GEN7(ring), irqs);
>>>>> +
>>>>> +	/* tell DE to send (all) flip_done to GuC */
>>>>> +	irqs = DERRMR_PIPEA_PRI_FLIP_DONE | DERRMR_PIPEA_SPR_FLIP_DONE |
>>>>> +	       DERRMR_PIPEB_PRI_FLIP_DONE | DERRMR_PIPEB_SPR_FLIP_DONE |
>>>>> +	       DERRMR_PIPEC_PRI_FLIP_DONE | DERRMR_PIPEC_SPR_FLIP_DONE;
>>>>> +	/* Unmasked bits will cause GuC response message to be sent */
>>>>> +	I915_WRITE(DE_GUCRMR, ~irqs);
>>>>
>>>> That's scary since userspace depends on a few more DERRMR events
>>>> (wait-for-scanline). Where will they end up?
>>>> -Chris
>>>
>>> This doesn't change any bits in DE_RRMR, or set the VBLANK or SCANLINE
>>> bits in the DE_GUCRMR, so those events should be unaffected. The GuC
>>> isn't interested in those, only in flip done.
>>
>> Why does the guc care about flip_done? With atomic it'll get exactly none
>> of those, ever ...
> 
> Well I forgot that mmio writes also generate interrupts. Still strange
> that GuC is interested in this. Would be really interesting to know what
> GuC is up to here.
> -Daniel

Maybe Alex knows ... otherwise we can ask the GuC f/w team ...

.Dave.

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