From d0bb96b4be69feea97f16de5306c35e280658931 Mon Sep 17 00:00:00 2001 From: Dhinakaran Pandiyan Date: Fri, 2 Feb 2018 21:13:01 -0800 Subject: drm/vblank: Restoring vblank counts after device PM events. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Cc: Chris Wilson Cc: Michel Dänzer Signed-off-by: Dhinakaran Pandiyan Reviewed-by: Rodrigo Vivi Acked-by: Daniel Vetter Signed-off-by: Rodrigo Vivi Link: https://patchwork.freedesktop.org/patch/msgid/20180203051302.9974-9-dhinakaran.pandiyan@intel.com --- drivers/gpu/drm/drm_vblank.c | 59 ++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 59 insertions(+) (limited to 'drivers/gpu/drm/drm_vblank.c') diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c index 913954765d9e..c781cb426bf1 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, + "Cannot compute missed vblanks without frame duration\n"); + 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); + + 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); +} +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) { -- cgit v1.2.3