Re: [PATCH v10] drm/i915: Replaced Blitter ring based flips with MMIO flips

["Gupta, Sourab" <sourab.gupta@intel.com>]

On Mon, 2014-06-02 at 06:56 +0000, Chris Wilson wrote:
> On Sun, Jun 01, 2014 at 04:43:13PM +0530, sourab.gupta@intel.com wrote:
> > From: Sourab Gupta <sourab.gupta@intel.com>
> > 
> > This patch enables the framework for using MMIO based flip calls,
> > in contrast with the CS based flip calls which are being used currently.
> > 
> > MMIO based flip calls can be enabled on architectures where
> > Render and Blitter engines reside in different power wells. The
> > decision to use MMIO flips can be made based on workloads to give
> > 100% residency for Media power well.
> > 
> > v2: The MMIO flips now use the interrupt driven mechanism for issuing the
> > flips when target seqno is reached. (Incorporating Ville's idea)
> > 
> > v3: Rebasing on latest code. Code restructuring after incorporating
> > Damien's comments
> > 
> > v4: Addressing Ville's review comments
> >     -general cleanup
> >     -updating only base addr instead of calling update_primary_plane
> >     -extending patch for gen5+ platforms
> > 
> > v5: Addressed Ville's review comments
> >     -Making mmio flip vs cs flip selection based on module parameter
> >     -Adding check for DRIVER_MODESET feature in notify_ring before calling
> >      notify mmio flip.
> >     -Other changes mostly in function arguments
> > 
> > v6: -Having a seperate function to check condition for using mmio flips (Ville)
> >     -propogating error code from i915_gem_check_olr (Ville)
> > 
> > v7: -Adding __must_check with i915_gem_check_olr (Chris)
> >     -Renaming mmio_flip_data to mmio_flip (Chris)
> >     -Rebasing on latest nightly
> > 
> > v8: -Rebasing on latest code
> >     -squash 3rd patch in series(mmio setbase vs page flip race) with this patch
> >     -Added new tiling mode update in intel_do_mmio_flip (Chris)
> > 
> > v9: -check for obj->last_write_seqno being 0 instead of obj->ring being NULL in
> > intel_postpone_flip, as this is a more restrictive condition (Chris)
> > 
> > v10: -Applied Chris's suggestions for squashing patches 2,3 into this patch.
> > These patches make the selection of CS vs MMIO flip at the page flip time, and
> > make the module parameter for using mmio flips as tristate, the states being
> > 'force CS flips', 'force mmio flips', 'driver discretion'.
> > Changed the logic for driver discretion (Chris)
> > 
> > Reviewed-by: Chris Wilson <chris@chris-wilson.co.uk>
> > Signed-off-by: Sourab Gupta <sourab.gupta@intel.com>
> > Signed-off-by: Akash Goel <akash.goel@intel.com>
> Tested-by: Chris Wilson <chris@chris-wilson.co.uk> # snb, ivb
> 
> Really happy with this now, just a few irrelevant bikesheds.
> 
> > -static int
> > +__must_check int
> >  i915_gem_check_olr(struct intel_engine_cs *ring, u32 seqno)
> >  {
> 
> Only the declaration requires the __must_check attribute, we don't need
> it here as well.
> 
> >  	int ret;
> > diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c
> > index 4ef6423..e0edb1f 100644
> > --- a/drivers/gpu/drm/i915/i915_irq.c
> > +++ b/drivers/gpu/drm/i915/i915_irq.c
> > @@ -1218,6 +1218,9 @@ static void notify_ring(struct drm_device *dev,
> >  
> >  	trace_i915_gem_request_complete(ring);
> >  
> > +	if (drm_core_check_feature(dev, DRIVER_MODESET))
> > +		intel_notify_mmio_flip(ring);
> > +
> 
> I wish Ville had suggested making UMS do the extra work of setting up
> the spinlock instead.
> 
> > +static bool use_mmio_flip(struct intel_engine_cs *ring,
> > +			  struct drm_i915_gem_object *obj)
> > +{
> > +	 /* This is not being used for older platforms, because
> > +	 * non-availability of flip done interrupt forces us to use
> > +	 * CS flips. Older platforms derive flip done using some clever
> > +	 * tricks involving the flip_pending status bits and vblank irqs.
> > +	 * So using MMIO flips there would disrupt this mechanism.
> > +	 */
> > +
> > +	if (INTEL_INFO(ring->dev)->gen < 5)
> > +		return false;
> > +
> > +	if (i915.use_mmio_flip < 0)
> > +		return false;
> > +	else if (i915.use_mmio_flip > 0)
> > +		return true;
> > +	else
> > +		return ring != obj->ring;
> > +}
> 
> Check whitespace.
> 
Hi Chris,
Couldn't get the whitespace error here, and at other places. Also,
checkpatch.pl doesn't show any. Can you please point out the error.
Thanks,
Sourab
> > +
> > +static void intel_do_mmio_flip(struct intel_crtc *intel_crtc)
> > +{
> > +	struct drm_device *dev = intel_crtc->base.dev;
> > +	struct drm_i915_private *dev_priv = dev->dev_private;
> > +	struct intel_framebuffer *intel_fb =
> > +		to_intel_framebuffer(intel_crtc->base.primary->fb);
> > +	struct drm_i915_gem_object *obj = intel_fb->obj;
> > +	u32 dspcntr;
> > +	u32 reg;
> > +
> > +	intel_mark_page_flip_active(intel_crtc);
> > +
> > +	reg = DSPCNTR(intel_crtc->plane);
> > +	dspcntr = I915_READ(reg);
> > +
> > +	if (INTEL_INFO(dev)->gen >= 4) {
> > +		if (obj->tiling_mode != I915_TILING_NONE)
> > +			dspcntr |= DISPPLANE_TILED;
> > +		else
> > +			dspcntr &= ~DISPPLANE_TILED;
> > +	}
> > +	I915_WRITE(reg, dspcntr);
> > +
> > +	I915_WRITE(DSPSURF(intel_crtc->plane),
> > +			intel_crtc->unpin_work->gtt_offset);
> > +	POSTING_READ(DSPSURF(intel_crtc->plane));
> > +}
> > +
> > +static int intel_postpone_flip(struct drm_i915_gem_object *obj)
> > +{
>         struct intel_engine_cs *ring = obj->ring; // will save our eyes
> > +	int ret;
> > +
> 
>         // I had to go back and check the locking, so save the
> 	// next person the same task.
>         lockdep_assert_held(&obj->base.dev->struct_mutex);
> 
> > +	if (!obj->last_write_seqno)
> > +		return 0;
> > +
> > +	if (i915_seqno_passed(obj->ring->get_seqno(obj->ring, true),
> > +				obj->last_write_seqno))
> > +		return 0;
> > +
> > +	ret = i915_gem_check_olr(obj->ring, obj->last_write_seqno);
> > +	if (ret)
> > +		return ret;
> > +
> > +	if (WARN_ON(!obj->ring->irq_get(obj->ring)))
> > +		return 0;
> > +
> > +	return 1;
> > +}
> > +
> > +void intel_notify_mmio_flip(struct intel_engine_cs *ring)
> > +{
> > +	struct drm_i915_private *dev_priv = ring->dev->dev_private;
> 
> 	struct drm_i915_private *dev_priv = to_i915(ring->dev);
> 
> > +	struct intel_crtc *intel_crtc;
> > +	unsigned long irq_flags;
> > +	u32 seqno;
> > +
> > +	seqno = ring->get_seqno(ring, false);
> > +
> > +	spin_lock_irqsave(&dev_priv->mmio_flip_lock, irq_flags);
> > +	for_each_intel_crtc(ring->dev, intel_crtc) {
> > +		struct intel_mmio_flip *mmio_flip;
> > +
> > +		mmio_flip = &intel_crtc->mmio_flip;
> > +		if (mmio_flip->seqno == 0)
> > +			continue;
> > +
> > +		if (ring->id != mmio_flip->ring_id)
> > +			continue;
> > +
> > +		if (i915_seqno_passed(seqno, mmio_flip->seqno)) {
> > +			intel_do_mmio_flip(intel_crtc);
> > +			mmio_flip->seqno = 0;
> > +			ring->irq_put(ring);
> > +		}
> > +	}
> > +	spin_unlock_irqrestore(&dev_priv->mmio_flip_lock, irq_flags);
> > +}
> > +
> > +static int intel_queue_mmio_flip(struct drm_device *dev,
> > +		struct drm_crtc *crtc,
> > +		struct drm_framebuffer *fb,
> > +		struct drm_i915_gem_object *obj,
> > +		struct intel_engine_cs *ring,
> > +		uint32_t flags)
> > +{
> > +	struct drm_i915_private *dev_priv = dev->dev_private;
> > +	struct intel_crtc *intel_crtc = to_intel_crtc(crtc);
> > +	unsigned long irq_flags;
> > +	int ret;
> > +
> > +	if (WARN_ON(intel_crtc->mmio_flip.seqno))
> > +		return -EBUSY;
> > +
> > +	ret = intel_postpone_flip(obj);
> > +	if (ret < 0)
> > +		return ret;
> > +	 if (ret == 0) {
> > +		intel_do_mmio_flip(intel_crtc);
> > +		return 0;
> > +	}
> > +
> > +	spin_lock_irqsave(&dev_priv->mmio_flip_lock, irq_flags);
> > +	intel_crtc->mmio_flip.seqno = obj->last_write_seqno;
> > +	intel_crtc->mmio_flip.ring_id = obj->ring->id;
> > +	spin_unlock_irqrestore(&dev_priv->mmio_flip_lock, irq_flags);
> > +
> > +	/* Double check to catch cases where irq fired before
> > +	 * mmio flip data was ready
> > +	 */
> > +	intel_notify_mmio_flip(obj->ring);
> > +	return 0;
> > +}
> 
> Check whitespace.
> -Chris
>