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| author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-02-09 11:15:23 +0100 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2021-02-10 12:38:55 +0100 |
| commit | f66aaab828e726986d9d5daa2b637b2712464a15 (patch) | |
| tree | e6ae581e30780c387b21a44bf8189f8cd51c4781 | |
| parent | c0f6f0c471a378a6da5ac99a086ba63e1a8570bb (diff) | |
| download | linux-f66aaab828e726986d9d5daa2b637b2712464a15.tar.gz linux-f66aaab828e726986d9d5daa2b637b2712464a15.tar.bz2 linux-f66aaab828e726986d9d5daa2b637b2712464a15.zip | |
drm/vblank: Document drm_crtc_vblank_restore constraints
I got real badly confused when trying to review a fix from Ville for
this. Let's try to document better what's required for this, and check
the minimal settings at runtime - we can't check ofc that there's
indeed no races in the driver callback.
Also noticed that the drm_vblank_restore version is unused, so lets
unexport that while at it.
Reviewed-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Cc: Ville Syrjala <ville.syrjala@linux.intel.com>
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20210209101523.2954281-1-daniel.vetter@ffwll.ch
| -rw-r--r-- | drivers/gpu/drm/drm_vblank.c | 25 | ||||
| -rw-r--r-- | include/drm/drm_vblank.h | 1 |
2 files changed, 10 insertions, 16 deletions
diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 893165eeddf3..2bd989688eae 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1470,20 +1470,7 @@ void drm_crtc_vblank_on(struct drm_crtc *crtc) } EXPORT_SYMBOL(drm_crtc_vblank_on); -/** - * drm_vblank_restore - estimate missed vblanks and update vblank count. - * @dev: DRM device - * @pipe: CRTC index - * - * Power manamement features can cause frame counter resets between vblank - * disable and enable. Drivers can use this function in their - * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since - * the last &drm_crtc_funcs.disable_vblank using timestamps and update the - * vblank counter. - * - * This function is the legacy version of drm_crtc_vblank_restore(). - */ -void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) +static void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) { ktime_t t_vblank; struct drm_vblank_crtc *vblank; @@ -1519,7 +1506,6 @@ void drm_vblank_restore(struct drm_device *dev, unsigned int pipe) diff, diff_ns, framedur_ns, cur_vblank - vblank->last); store_vblank(dev, pipe, diff, t_vblank, cur_vblank); } -EXPORT_SYMBOL(drm_vblank_restore); /** * drm_crtc_vblank_restore - estimate missed vblanks and update vblank count. @@ -1530,9 +1516,18 @@ EXPORT_SYMBOL(drm_vblank_restore); * &drm_crtc_funcs.enable_vblank implementation to estimate missed vblanks since * the last &drm_crtc_funcs.disable_vblank using timestamps and update the * vblank counter. + * + * Note that drivers must have race-free high-precision timestamping support, + * i.e. &drm_crtc_funcs.get_vblank_timestamp must be hooked up and + * &drm_driver.vblank_disable_immediate must be set to indicate the + * time-stamping functions are race-free against vblank hardware counter + * increments. */ void drm_crtc_vblank_restore(struct drm_crtc *crtc) { + WARN_ON_ONCE(!crtc->funcs->get_vblank_timestamp); + WARN_ON_ONCE(!crtc->dev->vblank_disable_immediate); + drm_vblank_restore(crtc->dev, drm_crtc_index(crtc)); } EXPORT_SYMBOL(drm_crtc_vblank_restore); diff --git a/include/drm/drm_vblank.h b/include/drm/drm_vblank.h index dd125f8c766c..733a3e2d1d10 100644 --- a/include/drm/drm_vblank.h +++ b/include/drm/drm_vblank.h @@ -247,7 +247,6 @@ 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); void drm_calc_timestamping_constants(struct drm_crtc *crtc, |