On Fri, Jan 12, 2018 at 09:57:06PM +0000, Dhinakaran Pandiyan wrote:
The HW frame counter can get reset if device enters a low power state after vblank interrupts were disabled. This messes up any following vblank count update as a negative diff (huge unsigned diff) is calculated from the HW frame counter change. We cannot ignore negative diffs altogther as there could be legitimate wrap arounds. So, allow drivers to update vblank->count with missed vblanks for the time interrupts were disabled. This is similar to _crtc_vblank_on() except that vblanks interrupts are not enabled at the end as this function is expected to be called from the driver _enable_vblank() vfunc.
v2: drm_crtc_vblank_restore should take crtc as arg. (Chris) Add docs and sprinkle some asserts.
Cc: Daniel Vetter daniel.vetter@ffwll.ch Cc: Chris Wilson chris@chris-wilson.co.uk Cc: Michel Dänzer michel@daenzer.net Signed-off-by: Dhinakaran Pandiyan dhinakaran.pandiyan@intel.com
drivers/gpu/drm/drm_vblank.c | 59 ++++++++++++++++++++++++++++++++++++++++++++ include/drm/drm_vblank.h | 2 ++ 2 files changed, 61 insertions(+)
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 2559d2d7b907..2690966694f0 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1237,6 +1237,65 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc) } EXPORT_SYMBOL(drm_crtc_vblank_on);
+/**
- drm_vblank_restore - estimated vblanks using timestamps and update it.
- Power manamement features can cause frame counter resets between vblank
- disable and enable. Drivers can then use this function in their
- &drm_crtc_funcs.enable_vblank implementation to estimate the vblanks since
- the last &drm_crtc_funcs.disable_vblank.
- This function is the legacy version of drm_crtc_vblank_restore().
- */
+void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) +{
- ktime_t t_vblank;
- struct drm_vblank_crtc *vblank;
- int framedur_ns;
- u64 diff_ns;
- u32 cur_vblank, diff = 1;
- int count = DRM_TIMESTAMP_MAXRETRIES;
- if (WARN_ON(pipe >= dev->num_crtcs))
return;- assert_spin_locked(&dev->vbl_lock);
- assert_spin_locked(&dev->vblank_time_lock);
- vblank = &dev->vblank[pipe];
- WARN_ONCE((drm_debug & DRM_UT_VBL) && !vblank->framedur_ns,
do we really only need this warn on debug vlb?
"Cannot compute missed vblanks without frame duration\n");
The message seems hard... if we *cannot* why do we move fwd?
- framedur_ns = vblank->framedur_ns;
- do {
cur_vblank = __get_vblank_counter(dev, pipe);drm_get_last_vbltimestamp(dev, pipe, &t_vblank, false);- } while (cur_vblank != __get_vblank_counter(dev, pipe) && --count > 0);
Based on the commend of drm_update_vblank_count I don't feel that we have to do the loop here... And if we have maybe we should re-org things to avoid duplication?
- diff_ns = ktime_to_ns(ktime_sub(t_vblank, vblank->time));
- if (framedur_ns)
diff = DIV_ROUND_CLOSEST_ULL(diff_ns, framedur_ns);- DRM_DEBUG_VBL("missed %d vblanks in %lld ns, frame duration=%d ns, hw_diff=%d\n",
diff, diff_ns, framedur_ns, cur_vblank - vblank->last);- store_vblank(dev, pipe, diff, t_vblank, cur_vblank);
hm... I wonder if the simple store_vblank(... __get_vblank_counter(dev, pipe)); wouldn't work here...
+} +EXPORT_SYMBOL(drm_vblank_restore);
+/**
- drm_crtc_vblank_restore - estimate vblanks using timestamps and update it.
- Power manamement features can cause frame counter resets between vblank
- disable and enable. Drivers can then use this function in their
- &drm_crtc_funcs.enable_vblank implementation to estimate the vblanks since
- the last &drm_crtc_funcs.disable_vblank.
- */
+void drm_crtc_vblank_restore(struct drm_crtc *crtc) +{
- drm_vblank_restore(crtc->dev, drm_crtc_index(crtc));
+} +EXPORT_SYMBOL(drm_crtc_vblank_restore);
static void drm_legacy_vblank_pre_modeset(struct drm_device *dev, unsigned int pipe) { diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index a4c3b0a0a197..16d46e2a6854 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -180,6 +180,8 @@ void drm_crtc_vblank_off(struct drm_crtc *crtc); void drm_crtc_vblank_reset(struct drm_crtc *crtc); void drm_crtc_vblank_on(struct drm_crtc *crtc); u64 drm_crtc_accurate_vblank_count(struct drm_crtc *crtc); +void drm_vblank_restore(struct drm_device *dev, unsigned int pipe); +void drm_crtc_vblank_restore(struct drm_crtc *crtc);
bool drm_calc_vbltimestamp_from_scanoutpos(struct drm_device *dev, unsigned int pipe, int *max_error, -- 2.11.0