On Fri, Jan 17, 2014 at 01:51:12PM -0200, Paulo Zanoni wrote:
> From: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
>
> Add a nice comment explaining why we shouldn't wait for a vblank on
> all cases, wait based on the HW gen, and add a comment saying we
> should probably skip that wait on some of the previous HW gens.
>
> Signed-off-by: Paulo Zanoni <paulo.r.zanoni@xxxxxxxxx>
Reviewed-by: Damien Lespiau <damien.lespiau@xxxxxxxxx>
Looking at BSpec for info on this, I didn't find any mention of having
to wait of a vblank indeed. There's a nice workaround we don't seem to
implement though (underrun when switching from one to multi-pipes,
display buffer related). I'm sure that's somewhere in a TODO list :)
--
Damien
> ---
> drivers/gpu/drm/i915/intel_display.c | 21 ++++++++++++++-------
> 1 file changed, 14 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
> index b110da8..9f356f9 100644
> --- a/drivers/gpu/drm/i915/intel_display.c
> +++ b/drivers/gpu/drm/i915/intel_display.c
> @@ -1745,12 +1745,11 @@ static void lpt_disable_pch_transcoder(struct drm_i915_private *dev_priv)
> /**
> * intel_enable_pipe - enable a pipe, asserting requirements
> * @crtc: crtc responsible for the pipe
> - * @wait_for_vblank: whether we should for a vblank or not after enabling it
> *
> * Enable @crtc's pipe, making sure that various hardware specific requirements
> * are met, if applicable, e.g. PLL enabled, LVDS pairs enabled, etc.
> */
> -static void intel_enable_pipe(struct intel_crtc *crtc, bool wait_for_vblank)
> +static void intel_enable_pipe(struct intel_crtc *crtc)
> {
> struct drm_device *dev = crtc->base.dev;
> struct drm_i915_private *dev_priv = dev->dev_private;
> @@ -1797,7 +1796,15 @@ static void intel_enable_pipe(struct intel_crtc *crtc, bool wait_for_vblank)
>
> I915_WRITE(reg, val | PIPECONF_ENABLE);
> POSTING_READ(reg);
> - if (wait_for_vblank)
> +
> + /*
> + * There's no guarantee the pipe will really start running now. It
> + * depends on the Gen, the output type and the relative order between
> + * pipe and plane enabling. Avoid waiting on HSW+ since it's not
> + * necessary.
> + * TODO: audit the previous gens.
> + */
> + if (INTEL_INFO(dev)->gen <= 7 && !IS_HASWELL(dev))
> intel_wait_for_vblank(dev_priv->dev, pipe);
> }
>
> @@ -3561,7 +3568,7 @@ static void ironlake_crtc_enable(struct drm_crtc *crtc)
> intel_crtc_load_lut(crtc);
>
> intel_update_watermarks(crtc);
> - intel_enable_pipe(intel_crtc, true);
> + intel_enable_pipe(intel_crtc);
> intel_enable_primary_plane(dev_priv, plane, pipe);
> intel_enable_planes(crtc);
> intel_crtc_update_cursor(crtc, true);
> @@ -3706,7 +3713,7 @@ static void haswell_crtc_enable(struct drm_crtc *crtc)
> intel_ddi_enable_transcoder_func(crtc);
>
> intel_update_watermarks(crtc);
> - intel_enable_pipe(intel_crtc, false);
> + intel_enable_pipe(intel_crtc);
>
> if (intel_crtc->config.has_pch_encoder)
> lpt_pch_enable(crtc);
> @@ -4131,7 +4138,7 @@ static void valleyview_crtc_enable(struct drm_crtc *crtc)
> intel_crtc_load_lut(crtc);
>
> intel_update_watermarks(crtc);
> - intel_enable_pipe(intel_crtc, true);
> + intel_enable_pipe(intel_crtc);
> intel_enable_primary_plane(dev_priv, plane, pipe);
> intel_enable_planes(crtc);
> intel_crtc_update_cursor(crtc, true);
> @@ -4169,7 +4176,7 @@ static void i9xx_crtc_enable(struct drm_crtc *crtc)
> intel_crtc_load_lut(crtc);
>
> intel_update_watermarks(crtc);
> - intel_enable_pipe(intel_crtc, true);
> + intel_enable_pipe(intel_crtc);
> intel_enable_primary_plane(dev_priv, plane, pipe);
> intel_enable_planes(crtc);
> /* The fixup needs to happen before cursor is enabled */
> --
> 1.8.4.2
>
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