[PATCH v3 1/1] drm/vblank: drop use of DRM_WAIT_ON()

[Michel Dänzer]

On 2019-07-26 11:06 p.m., Sam Ravnborg wrote:
> DRM_WAIT_ON() is from the deprecated drm_os_linux header and
> the modern replacement is the wait_event_*.
> 
> The return values differ, so a conversion is needed to
> keep the original interface towards userspace.
> Introduced a switch/case to make code obvious.
> 
> Analysis from Michel Dänzer:
> 
> The waiting condition rely on all relevant places where vblank_count
> is modified calls wake_up(&vblank->queue).
> 
> drm_handle_vblank():
> - Calls wake_up(&vblank->queue)
> 
> drm_vblank_enable():
> - There is no need here because there can be no sleeping waiters
>   in the queue, because vblank->enabled == false immediately
>   terminates any waits.
> 
> drm_crtc_accurate_vblank_count():
> - This is called from interrupt handlers, at least from
>   amdgpu_dm.c:dm_pflip_high_irq(). Not sure it needs to wake up
>   the queue though, the driver should call
>   drm_(crtc_)_handle_vblank anyway.
> 
> drm_vblank_disable_and_save():
> - It can be called from an interrupt, via drm_handle_vblank ->
>   vblank_disable_fn. However, the only place where
>   drm_vblank_disable_and_save can be called with sleeping waiters
>   in the queue is in drm_crtc_vblank_off, which wakes up the queue
>   afterwards (which terminates all waits, because
>   vblank->enabled == false at this point).
> 
> v3:
> - Added analysis to changelog from Michel Dänzer
> - Moved return result handling inside if (req_seq != seq) (Daniel V)
> - Reused more of the former logic - resulting in simpler code
> - Dropped Reviewed-by from Sean Paul as this is a new implmentation
> 
> v2:
> - Fix so the case where req_seq equals seq was handled properly
> - quick hack to check if IGT became happy
> - Only sent to igt, not to dri-devel
> 
> Signed-off-by: Sam Ravnborg <sam at ravnborg.org>
> Cc: "Michel Dänzer" <michel at daenzer.net>
> Cc: Sean Paul <sean at poorly.run>
> Cc: Maarten Lankhorst <maarten.lankhorst at linux.intel.com>
> Cc: Maxime Ripard <maxime.ripard at bootlin.com>
> Cc: David Airlie <airlied at linux.ie>
> Cc: Daniel Vetter <daniel at ffwll.ch>

Reviewed-by: Michel Dänzer <michel.daenzer at amd.com>


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Earthling Michel Dänzer               |              https://www.amd.com
Libre software enthusiast             |             Mesa and X developer