On Tue, Feb 09, 2021 at 05:36:07PM +0200, Ville Syrjälä wrote:

On Tue, Feb 09, 2021 at 11:15:23AM +0100, Daniel Vetter wrote:

...

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.

Cc: Ville Syrjala ville.syrjala@linux.intel.com Signed-off-by: Daniel Vetter daniel.vetter@intel.com

---

drivers/gpu/drm/drm_vblank.c | 25 ++++++++++--------------- 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 c914b14cfb43..05f4d4c078fd 100644 --- a/drivers/gpu/drm/drm_vblank.c +++ b/drivers/gpu/drm/drm_vblank.c @@ -1471,20 +1471,7 @@ 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; @@ -1520,7 +1507,6 @@ 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.

@@ -1531,9 +1517,18 @@ 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.

Looks good. Might prevent someone from shooting themselves in the foot.

Yeah hopefully, maybe even me :-)

Reviewed-by: Ville Syrjälä ville.syrjala@linux.intel.com

Thanks for your review, I pushed to drm-misc-next. -Daniel

...

*/ 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,

2.30.0

-- Ville Syrjälä Intel