[PATCH 24/26] drm/i915: wait for a vblank instead of 50ms when enabling FBC

Paulo Zanoni
2015-10-27T16:51:15Z

Instead of waiting for 50ms, just wait until the next vblank, since
it's the minimum requirement.

This moves PC7 residency on my specific BDW machine running Cinnamon
from 60-70% to 84-89%. Without FBC, I get 20-25%. I'm using a
3200x1800 eDP panel.

Signed-off-by: Paulo Zanoni <paulo.r.zanoni@intel.com>
---
drivers/gpu/drm/i915/i915_drv.h | 2 +-
drivers/gpu/drm/i915/intel_fbc.c | 12 +++---------
2 files changed, 4 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_drv.h b/drivers/gpu/drm/i915/i915_drv.h
index fdbe068..784ce2e 100644
--- a/drivers/gpu/drm/i915/i915_drv.h
+++ b/drivers/gpu/drm/i915/i915_drv.h
@@ -918,9 +918,9 @@ struct i915_fbc {

struct intel_fbc_work {
bool scheduled;
+ u32 scheduled_vblank;
struct work_struct work;
struct drm_framebuffer *fb;
- unsigned long enable_jiffies;
} work;

const char *no_fbc_reason;
diff --git a/drivers/gpu/drm/i915/intel_fbc.c b/drivers/gpu/drm/i915/intel_fbc.c
index a7192dd..cbdf2f3 100644
--- a/drivers/gpu/drm/i915/intel_fbc.c
+++ b/drivers/gpu/drm/i915/intel_fbc.c
@@ -448,7 +448,6 @@ static void intel_fbc_work_fn(struct work_struct *__work)
container_of(__work, struct drm_i915_private, fbc.work.work);
struct intel_fbc_work *work = &dev_priv->fbc.work;
struct intel_crtc *crtc = dev_priv->fbc.crtc;
- unsigned long delay_jiffies = msecs_to_jiffies(50);

retry:
/* Delay the actual enabling to let pageflipping cease and the
@@ -457,14 +456,9 @@ retry:
* vblank to pass after disabling the FBC before we attempt
* to modify the control registers.
*
- * A more complicated solution would involve tracking vblanks
- * following the termination of the page-flipping sequence
- * and indeed performing the enable as a co-routine and not
- * waiting synchronously upon the vblank.
- *
* WaFbcWaitForVBlankBeforeEnable:ilk,snb
*/
- wait_remaining_ms_from_jiffies(work->enable_jiffies, delay_jiffies);
+ intel_wait_for_vblank(dev_priv->dev, crtc->pipe);

mutex_lock(&dev_priv->fbc.lock);

@@ -473,7 +467,7 @@ retry:
goto out;

/* Were we delayed again while this function was sleeping? */
- if (time_after(work->enable_jiffies + delay_jiffies, jiffies)) {
+ if (drm_crtc_vblank_get(&crtc->base) == work->scheduled_vblank) {
mutex_unlock(&dev_priv->fbc.lock);
goto retry;
}
@@ -506,7 +500,7 @@ static void intel_fbc_schedule_activation(struct intel_crtc *crtc)
* jiffy count. */
work->fb = crtc->base.primary->fb;
work->scheduled = true;
- work->enable_jiffies = jiffies;
+ work->scheduled_vblank = drm_crtc_vblank_count(&crtc->base);

schedule_work(&work->work);