Cc: Ville and Daniel for archeology...
On Fri, 11 Jun 2021, Nischal Varide <[email protected]> wrote: > If the panel is 12bpc then Dithering is not enabled in the Legacy > dithering block , instead its Enabled after the C1 CC1 pipe post > color space conversion.For a 6bpc pannel Dithering is enabled in > Legacy block. Currently, we only ever enable dithering for 6 bpc displays. See commit e8fa4270536d ("drm/i915: Only dither on 6bpc panels"). This is decided at the end of intel_modeset_pipe_config(). The big question here is if we want to expand the use of dithering. I guess we could be able to reduce banding if we did? > Signed-off-by: Nischal Varide <[email protected]> > --- > drivers/gpu/drm/i915/display/intel_color.c | 7 +++++++ > drivers/gpu/drm/i915/display/intel_display.c | 11 ++++++++++- > drivers/gpu/drm/i915/i915_reg.h | 1 + > 3 files changed, 18 insertions(+), 1 deletion(-) > > diff --git a/drivers/gpu/drm/i915/display/intel_color.c > b/drivers/gpu/drm/i915/display/intel_color.c > index dab892d2251b..c7af583200c4 100644 > --- a/drivers/gpu/drm/i915/display/intel_color.c > +++ b/drivers/gpu/drm/i915/display/intel_color.c > @@ -1574,6 +1574,7 @@ static int glk_color_check(struct intel_crtc_state > *crtc_state) > static u32 icl_gamma_mode(const struct intel_crtc_state *crtc_state) > { > u32 gamma_mode = 0; > + struct drm_i915_private *i915 = to_i915(crtc_state->uapi.crtc->dev); > > if (crtc_state->hw.degamma_lut) > gamma_mode |= PRE_CSC_GAMMA_ENABLE; > @@ -1588,6 +1589,12 @@ static u32 icl_gamma_mode(const struct > intel_crtc_state *crtc_state) > else > gamma_mode |= GAMMA_MODE_MODE_12BIT_MULTI_SEGMENTED; > > + if (DISPLAY_VER(i915) >= 13) { > + if (!crtc_state->dither_force_disable && > + (crtc_state->pipe_bpp == 36)) > + gamma_mode |= POST_CC1_DITHER_ENABLE; > + } This enables dithering independent of crtc_state->dither. That doesn't seem like a good idea. I think the decision should be made at the end of intel_modeset_pipe_config(). if (DISPLAY_VER(i915) >= 13 && crtc_state->dither && crtc_state->pipe_bpp == 36) gamma_mode |= POST_CC1_DITHER_ENABLE; Obviously, as we currently only enable dithering for 6 bpc, this would become a nop if it looked at crtc_state->dither and pipe_bpp only. > + > return gamma_mode; > } > > diff --git a/drivers/gpu/drm/i915/display/intel_display.c > b/drivers/gpu/drm/i915/display/intel_display.c > index 362bff9beb5c..3a7feb246745 100644 > --- a/drivers/gpu/drm/i915/display/intel_display.c > +++ b/drivers/gpu/drm/i915/display/intel_display.c > @@ -5762,7 +5762,16 @@ static void bdw_set_pipemisc(const struct > intel_crtc_state *crtc_state) > break; > } > > - if (crtc_state->dither) > + /* > + * If 12bpc panel then, Enables dithering after the CC1 pipe > + * post color space conversion and not here for display_ver > + * greater than or equal to thirteen. > + */ > + > + if (crtc_state->dither && (crtc_state->pipe_bpp != 36)) > + val |= PIPEMISC_DITHER_ENABLE | PIPEMISC_DITHER_TYPE_SP; > + > + if (crtc_state->dither && (crtc_state->pipe_bpp == 36) && > (DISPLAY_VER(dev_priv) < 13)) > val |= PIPEMISC_DITHER_ENABLE | PIPEMISC_DITHER_TYPE_SP; This is what you're trying to say: /* 12 bpc dithering is done at post CSC gamma for display 13+ */ if (crtc_state->dither && (crtc_state->pipe_bpp != 36 || DISPLAY_VER(dev_priv) < 13)) val |= PIPEMISC_DITHER_ENABLE | PIPEMISC_DITHER_TYPE_SP; Again, this is a nop until we decide to use dithering more. > > if (crtc_state->output_format == INTEL_OUTPUT_FORMAT_YCBCR420 || > diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h > index e915ec034c98..33dba13fa94d 100644 > --- a/drivers/gpu/drm/i915/i915_reg.h > +++ b/drivers/gpu/drm/i915/i915_reg.h > @@ -7743,6 +7743,7 @@ enum { > #define GAMMA_MODE(pipe) _MMIO_PIPE(pipe, _GAMMA_MODE_A, _GAMMA_MODE_B) > #define PRE_CSC_GAMMA_ENABLE (1 << 31) > #define POST_CSC_GAMMA_ENABLE (1 << 30) > +#define POST_CC1_DITHER_ENABLE (1 << 26) > #define GAMMA_MODE_MODE_MASK (3 << 0) > #define GAMMA_MODE_MODE_8BIT (0 << 0) > #define GAMMA_MODE_MODE_10BIT (1 << 0) -- Jani Nikula, Intel Open Source Graphics Center _______________________________________________ Intel-gfx mailing list [email protected] https://lists.freedesktop.org/mailman/listinfo/intel-gfx
