On Tue, 19 Apr 2011 12:12:38 -0700, Jesse Barnes <jbar...@virtuousgeek.org> wrote: > Figuring out which pipe bpp to use is a bit painful. It depends on both > the encoder and display configuration attached to a pipe. For instance, > to drive a 24bpp framebuffer out to an 18bpp panel, we need to use 6bpc > on the pipe but also enable dithering. But driving that same > framebuffer to a DisplayPort output on another pipe means using 8bpc and > no dithering. > > So split out and enhance the code to handle the various cases, returning > an appropriate pipe bpp as well as whether dithering should be enabled. > > Save the resulting pipe bpp in the intel_crtc struct for use by encoders > in calculating bandwidth requirements (defaults to 24bpp on pre-ILK). > > Signed-off-by: Jesse Barnes <jbar...@virtuousgeek.org> > --- > drivers/gpu/drm/i915/intel_display.c | 181 > ++++++++++++++++++++++++++-------- > drivers/gpu/drm/i915/intel_drv.h | 1 + > 2 files changed, 140 insertions(+), 42 deletions(-) > > diff --git a/drivers/gpu/drm/i915/intel_display.c > b/drivers/gpu/drm/i915/intel_display.c > index 8ef0c39..e81e418 100644 > --- a/drivers/gpu/drm/i915/intel_display.c > +++ b/drivers/gpu/drm/i915/intel_display.c > @@ -4232,6 +4232,120 @@ static inline bool intel_panel_use_ssc(struct > drm_i915_private *dev_priv) > return dev_priv->lvds_use_ssc && i915_panel_use_ssc; > } > > +/** > + * intel_choose_pipe_bpp - figure out what color depth the pipe should send > + * @crtc: CRTC structure > + * > + * A pipe may be connected to one or more outputs. Based on the depth of the > + * attached framebuffer, choose a good color depth to use on the pipe. > + * > + * If possible, match the pipe depth to the fb depth. In some cases, this > + * isn't ideal, because the connected output supports a lesser or restricted > + * set of depths. Resolve that here: > + * LVDS typically supports only 6bpc, so clamp down in that case > + * HDMI supports only 8bpc or 12bpc, so clamp to 8bpc with dither for > 10bpc > + * Displays may support a restricted set as well, check EDID and clamp as > + * appropriate. > + * > + * RETURNS: > + * Dithering requirement (i.e. false if display bpc and pipe bpc match, > + * true if they don't match). > + */ > +static bool intel_choose_pipe_bpp(struct drm_crtc *crtc, unsigned int > *pipe_bpp)
Should mention dithering in the name, perhaps
choose_pipe_bpp_and_dithering or some such? Perhaps returning the
dithering in another by-reference parameter?
> +{
> + struct drm_device *dev = crtc->dev;
> + struct drm_i915_private *dev_priv = dev->dev_private;
> + struct drm_encoder *encoder;
> + struct drm_connector *connector;
> + unsigned int display_bpc = UINT_MAX, fb_bpc, bpc;
> +
> + fb_bpc = crtc->fb->depth / 3;
> +
> + /* Walk the encoders & connectors on this crtc, get min bpc */
Don't you want the max bpc?
> +
> + /*
> + * We could just drive the pipe at the highest bpc all the time and
> + * enable dithering as needed, but that costs bandwidth. So choose
> + * the minimum value that expresses the full color range of the fb but
> + * also stays within the max display bpc discovered above.
> + */
> +
> + switch (crtc->fb->depth) {
> + case 8:
> + case 15:
> + case 16:
> + bpc = 6; /* min is 18bpp */
> + break;
> + case 24:
> + bpc = min((unsigned int)8, display_bpc);
> + break;
> + case 30:
> + bpc = min((unsigned int)10, display_bpc);
> + break;
> + case 48:
> + bpc = min((unsigned int)12, display_bpc);
> + break;
> + default:
> + DRM_DEBUG("unsupported depth, assuming 24 bits\n");
> + bpc = min((unsigned int)8, display_bpc);
> + break;
> + }
Hrm. 8-bit through a colormap should probably use 8 bpc? We can probably
ignore 15/16-bit direct color (which might want 8bpc as well).
The simple fix would be to use 8bpc on 8bpp and otherwise leave things alone.
--
keith.pack...@intel.com
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