diff options
author | Daniel Vetter <daniel.vetter@ffwll.ch> | 2016-10-12 08:22:25 +0200 |
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committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2016-10-12 08:22:25 +0200 |
commit | c0c8b9ed1b0c14d91ff73624df6d918bb47c8a5e (patch) | |
tree | 7fb6f2c7c028cd4926b827d3b5937c49afefa63a /drivers/gpu/drm/drm_irq.c | |
parent | 5a920b85f2c6e3fd7d9dd9bb3f3345e9085e2360 (diff) | |
parent | 69405d3da98b48633b78a49403e4f9cdb7c6a0f5 (diff) | |
download | op-kernel-dev-c0c8b9ed1b0c14d91ff73624df6d918bb47c8a5e.zip op-kernel-dev-c0c8b9ed1b0c14d91ff73624df6d918bb47c8a5e.tar.gz |
Merge tag 'drm-for-v4.9' into drm-intel-next-queued
It's been over two months, git definitely lost it's marbles. Conflicts
resolved by picking our version, plus manually checking the diff with
the parent in drm-intel-next-queued to make sure git didn't do
anything stupid. It did, so I removed 2 occasions where it
double-inserted a bit of code. The diff is now just
- kernel-doc changes
- drm format/name changes
- display-info changes
so looks all reasonable.
Signed-off-by: Daniel Vetter <daniel.vetter@intel.com>
Diffstat (limited to 'drivers/gpu/drm/drm_irq.c')
-rw-r--r-- | drivers/gpu/drm/drm_irq.c | 40 |
1 files changed, 34 insertions, 6 deletions
diff --git a/drivers/gpu/drm/drm_irq.c b/drivers/gpu/drm/drm_irq.c index c0c3f20..b969a64 100644 --- a/drivers/gpu/drm/drm_irq.c +++ b/drivers/gpu/drm/drm_irq.c @@ -713,10 +713,10 @@ EXPORT_SYMBOL(drm_calc_timestamping_constants); * Negative value on error, failure or if not supported in current * video mode: * - * -EINVAL - Invalid CRTC. - * -EAGAIN - Temporary unavailable, e.g., called before initial modeset. - * -ENOTSUPP - Function not supported in current display mode. - * -EIO - Failed, e.g., due to failed scanout position query. + * -EINVAL Invalid CRTC. + * -EAGAIN Temporary unavailable, e.g., called before initial modeset. + * -ENOTSUPP Function not supported in current display mode. + * -EIO Failed, e.g., due to failed scanout position query. * * Returns or'ed positive status flags on success: * @@ -1008,6 +1008,31 @@ static void send_vblank_event(struct drm_device *dev, * period. This helper function implements exactly the required vblank arming * behaviour. * + * NOTE: Drivers using this to send out the event in struct &drm_crtc_state + * as part of an atomic commit must ensure that the next vblank happens at + * exactly the same time as the atomic commit is committed to the hardware. This + * function itself does **not** protect again the next vblank interrupt racing + * with either this function call or the atomic commit operation. A possible + * sequence could be: + * + * 1. Driver commits new hardware state into vblank-synchronized registers. + * 2. A vblank happens, committing the hardware state. Also the corresponding + * vblank interrupt is fired off and fully processed by the interrupt + * handler. + * 3. The atomic commit operation proceeds to call drm_crtc_arm_vblank_event(). + * 4. The event is only send out for the next vblank, which is wrong. + * + * An equivalent race can happen when the driver calls + * drm_crtc_arm_vblank_event() before writing out the new hardware state. + * + * The only way to make this work safely is to prevent the vblank from firing + * (and the hardware from committing anything else) until the entire atomic + * commit sequence has run to completion. If the hardware does not have such a + * feature (e.g. using a "go" bit), then it is unsafe to use this functions. + * Instead drivers need to manually send out the event from their interrupt + * handler by calling drm_crtc_send_vblank_event() and make sure that there's no + * possible race with the hardware committing the atomic update. + * * Caller must hold event lock. Caller must also hold a vblank reference for * the event @e, which will be dropped when the next vblank arrives. */ @@ -1030,8 +1055,11 @@ EXPORT_SYMBOL(drm_crtc_arm_vblank_event); * @crtc: the source CRTC of the vblank event * @e: the event to send * - * Updates sequence # and timestamp on event, and sends it to userspace. - * Caller must hold event lock. + * Updates sequence # and timestamp on event for the most recently processed + * vblank, and sends it to userspace. Caller must hold event lock. + * + * See drm_crtc_arm_vblank_event() for a helper which can be used in certain + * situation, especially to send out events for atomic commit operations. */ void drm_crtc_send_vblank_event(struct drm_crtc *crtc, struct drm_pending_vblank_event *e) |