diff options
| author | Ville Syrjälä <ville.syrjala@linux.intel.com> | 2014-05-15 20:20:36 +0300 |
|---|---|---|
| committer | Daniel Vetter <daniel.vetter@ffwll.ch> | 2014-05-22 15:06:37 +0200 |
| commit | f75f3746e801504531bffc9f92e1d4a271705f7e (patch) | |
| tree | ce4b7c66a5c2880670bbd7cf74c9cb0375367d2d /drivers/gpu/drm/i915/i915_irq.c | |
| parent | 0b2a8e09f9b52b72b0436c84af647f1735d9528e (diff) | |
drm/i915: Draw a picture about video timings
The docs are a bit lacking when it comes to describing when certain
timing related events occur in the hardware. Draw a picture which
tries to capture the most important ones.
v2: Clarify a few details (Imre)
v3: Add HSW+ HDMI scanline counter numbers
Acked-by: Imre Deak <imre.deak@intel.com>
Reviewed-by: Akash Goel <akash.goels@gmail.com>
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Reviewed-by: "Sourab Gupta <sourabgupta@gmail.com>"
Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Diffstat (limited to 'drivers/gpu/drm/i915/i915_irq.c')
| -rw-r--r-- | drivers/gpu/drm/i915/i915_irq.c | 50 |
1 files changed, 50 insertions, 0 deletions
diff --git a/drivers/gpu/drm/i915/i915_irq.c b/drivers/gpu/drm/i915/i915_irq.c index 16880cf4c65a..087e76b9ee35 100644 --- a/drivers/gpu/drm/i915/i915_irq.c +++ b/drivers/gpu/drm/i915/i915_irq.c @@ -740,6 +740,56 @@ i915_pipe_enabled(struct drm_device *dev, int pipe) } } +/* + * This timing diagram depicts the video signal in and + * around the vertical blanking period. + * + * Assumptions about the fictitious mode used in this example: + * vblank_start >= 3 + * vsync_start = vblank_start + 1 + * vsync_end = vblank_start + 2 + * vtotal = vblank_start + 3 + * + * start of vblank: + * latch double buffered registers + * increment frame counter (ctg+) + * generate start of vblank interrupt (gen4+) + * | + * | frame start: + * | generate frame start interrupt (aka. vblank interrupt) (gmch) + * | may be shifted forward 1-3 extra lines via PIPECONF + * | | + * | | start of vsync: + * | | generate vsync interrupt + * | | | + * ___xxxx___ ___xxxx___ ___xxxx___ ___xxxx___ ___xxxx___ ___xxxx + * . \hs/ . \hs/ \hs/ \hs/ . \hs/ + * ----va---> <-----------------vb--------------------> <--------va------------- + * | | <----vs-----> | + * -vbs-----> <---vbs+1---> <---vbs+2---> <-----0-----> <-----1-----> <-----2--- (scanline counter gen2) + * -vbs-2---> <---vbs-1---> <---vbs-----> <---vbs+1---> <---vbs+2---> <-----0--- (scanline counter gen3+) + * -vbs-2---> <---vbs-2---> <---vbs-1---> <---vbs-----> <---vbs+1---> <---vbs+2- (scanline counter hsw+ hdmi) + * | | | + * last visible pixel first visible pixel + * | increment frame counter (gen3/4) + * pixel counter = vblank_start * htotal pixel counter = 0 (gen3/4) + * + * x = horizontal active + * _ = horizontal blanking + * hs = horizontal sync + * va = vertical active + * vb = vertical blanking + * vs = vertical sync + * vbs = vblank_start (number) + * + * Summary: + * - most events happen at the start of horizontal sync + * - frame start happens at the start of horizontal blank, 1-4 lines + * (depending on PIPECONF settings) after the start of vblank + * - gen3/4 pixel and frame counter are synchronized with the start + * of horizontal active on the first line of vertical active + */ + static u32 i8xx_get_vblank_counter(struct drm_device *dev, int pipe) { /* Gen2 doesn't have a hardware frame counter */ |