On Wed, Jan 15, 2020 at 01:16:33PM +0100, Thomas Zimmermann wrote:
> VBLANK interrupts can be disabled immediately or with a delay, where the
> latter is the default. The former option can be selected by setting
> get_vblank_timestamp, and enabling vblank_disable_immediate in struct
> drm_device.
>
> The setup is only evaluated once when DRM initializes VBLANKs. Evaluating
> the settings on each use of vblank_disable_immediate will allow for easy
> integration of CRTC VBLANK functions.
>
> Signed-off-by: Thomas Zimmermann <tzimmermann@xxxxxxx>
> ---
> drivers/gpu/drm/drm_vblank.c | 31 ++++++++++++++-----------------
> 1 file changed, 14 insertions(+), 17 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_vblank.c b/drivers/gpu/drm/drm_vblank.c
> index 3f1dd54cc8bb..abb085c67d82 100644
> --- a/drivers/gpu/drm/drm_vblank.c
> +++ b/drivers/gpu/drm/drm_vblank.c
> @@ -481,19 +481,6 @@ int drm_vblank_init(struct drm_device *dev, unsigned int num_crtcs)
>
> DRM_INFO("Supports vblank timestamp caching Rev 2 (21.10.2013).\n");
>
> - /* Driver specific high-precision vblank timestamping supported? */
> - if (dev->driver->get_vblank_timestamp)
> - DRM_INFO("Driver supports precise vblank timestamp query.\n");
> - else
> - DRM_INFO("No driver support for vblank timestamp query.\n");
> -
> - /* Must have precise timestamping for reliable vblank instant disable */
> - if (dev->vblank_disable_immediate && !dev->driver->get_vblank_timestamp) {
> - dev->vblank_disable_immediate = false;
> - DRM_INFO("Setting vblank_disable_immediate to false because "
> - "get_vblank_timestamp == NULL\n");
> - }
Which drivers are so broken they set vblank_disable_immediate to true
without having the vfunc specified? IMO this code should just go away
(or converted to a WARN).
> -
> return 0;
>
> err:
> @@ -1070,6 +1057,15 @@ int drm_crtc_vblank_get(struct drm_crtc *crtc)
> }
> EXPORT_SYMBOL(drm_crtc_vblank_get);
>
> +static bool __vblank_disable_immediate(struct drm_device *dev, unsigned int pipe)
> +{
> + if (!dev->vblank_disable_immediate)
> + return false;
> + if (!dev->driver->get_vblank_timestamp)
> + return false;
> + return true;
> +}
> +
> static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
> {
> struct drm_vblank_crtc *vblank = &dev->vblank[pipe];
> @@ -1086,7 +1082,7 @@ static void drm_vblank_put(struct drm_device *dev, unsigned int pipe)
> return;
> else if (drm_vblank_offdelay < 0)
> vblank_disable_fn(&vblank->disable_timer);
> - else if (!dev->vblank_disable_immediate)
> + else if (__vblank_disable_immediate(dev, pipe))
> mod_timer(&vblank->disable_timer,
> jiffies + ((drm_vblank_offdelay * HZ)/1000));
> }
> @@ -1663,7 +1659,7 @@ int drm_wait_vblank_ioctl(struct drm_device *dev, void *data,
> /* If the counter is currently enabled and accurate, short-circuit
> * queries to return the cached timestamp of the last vblank.
> */
> - if (dev->vblank_disable_immediate &&
> + if (__vblank_disable_immediate(dev, pipe) &&
> drm_wait_vblank_is_query(vblwait) &&
> READ_ONCE(vblank->enabled)) {
> drm_wait_vblank_reply(dev, pipe, &vblwait->reply);
> @@ -1820,7 +1816,7 @@ bool drm_handle_vblank(struct drm_device *dev, unsigned int pipe)
> * been signaled. The disable has to be last (after
> * drm_handle_vblank_events) so that the timestamp is always accurate.
> */
> - disable_irq = (dev->vblank_disable_immediate &&
> + disable_irq = (__vblank_disable_immediate(dev, pipe) &&
> drm_vblank_offdelay > 0 &&
> !atomic_read(&vblank->refcount));
>
> @@ -1893,7 +1889,8 @@ int drm_crtc_get_sequence_ioctl(struct drm_device *dev, void *data,
> pipe = drm_crtc_index(crtc);
>
> vblank = &dev->vblank[pipe];
> - vblank_enabled = dev->vblank_disable_immediate && READ_ONCE(vblank->enabled);
> + vblank_enabled = __vblank_disable_immediate(dev, pipe) &&
> + READ_ONCE(vblank->enabled);
>
> if (!vblank_enabled) {
> ret = drm_crtc_vblank_get(crtc);
> --
> 2.24.1
>
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--
Ville Syrjälä
Intel
