Since Haswell we have no color range indication either in the pipe or port registers for DP. Instead, there's a separate register for setting the DP Main Stream Attributes (MSA) directly. The MSA register definition makes no references to colorimetry, just a vague reference to the DP spec. The connection to the color range was lost.
Apparently we've failed to set the proper MSA bit for limited, or CEA, range ever since the first DDI platforms. We've started setting other MSA parameters since commit dae847991a43 ("drm/i915: add intel_ddi_set_pipe_settings").
Without the crucial bit of information, the DP sink has no way of knowing the source is actually transmitting limited range RGB, leading to "washed out" colors. With the colorimetry information, compliant sinks should be able to handle the limited range properly. Native (i.e. non-LSPCON) HDMI was not affected because we do pass the color range via AVI infoframes.
Though not the root cause, the problem was made worse for DDI platforms with commit 55bc60db5988 ("drm/i915: Add "Automatic" mode for the "Broadcast RGB" property"), which selects limited range RGB automatically based on the mode, as per the DP, HDMI and CEA specs.
After all these years, the fix boils down to flipping one bit.
[Per testing reports, this fixes DP sinks, but not the LSPCON. My educated guess is that the LSPCON fails to turn the CEA range MSA into AVI infoframes for HDMI.]
Reported-by: Michał Kopeć mkopec12@gmail.com Reported-by: N. W. nw9165-3201@yahoo.com Reported-by: Nicholas Stommel nicholas.stommel@gmail.com Reported-by: Tom Yan tom.ty89@gmail.com Tested-by: Nicholas Stommel nicholas.stommel@gmail.com References: https://bugs.freedesktop.org/show_bug.cgi?id=100023 Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=107476 Bugzilla: https://bugzilla.kernel.org/show_bug.cgi?id=94921 Cc: Paulo Zanoni paulo.r.zanoni@intel.com Cc: Rodrigo Vivi rodrigo.vivi@intel.com Cc: Ville Syrjälä ville.syrjala@linux.intel.com Cc: stable@vger.kernel.org # v3.9+ Signed-off-by: Jani Nikula jani.nikula@intel.com --- drivers/gpu/drm/i915/i915_reg.h | 1 + drivers/gpu/drm/i915/intel_ddi.c | 4 ++++ 2 files changed, 5 insertions(+)
diff --git a/drivers/gpu/drm/i915/i915_reg.h b/drivers/gpu/drm/i915/i915_reg.h index 17575cfc22b5..0c9f03dda569 100644 --- a/drivers/gpu/drm/i915/i915_reg.h +++ b/drivers/gpu/drm/i915/i915_reg.h @@ -9246,6 +9246,7 @@ enum skl_power_gate { #define TRANS_MSA_10_BPC (2 << 5) #define TRANS_MSA_12_BPC (3 << 5) #define TRANS_MSA_16_BPC (4 << 5) +#define TRANS_MSA_CEA_RANGE (1 << 3)
/* LCPLL Control */ #define LCPLL_CTL _MMIO(0x130040) diff --git a/drivers/gpu/drm/i915/intel_ddi.c b/drivers/gpu/drm/i915/intel_ddi.c index 0adc043529f2..6f7be066c8f2 100644 --- a/drivers/gpu/drm/i915/intel_ddi.c +++ b/drivers/gpu/drm/i915/intel_ddi.c @@ -1685,6 +1685,10 @@ void intel_ddi_set_pipe_settings(const struct intel_crtc_state *crtc_state) WARN_ON(transcoder_is_dsi(cpu_transcoder));
temp = TRANS_MSA_SYNC_CLK; + + if (crtc_state->limited_color_range) + temp |= TRANS_MSA_CEA_RANGE; + switch (crtc_state->pipe_bpp) { case 18: temp |= TRANS_MSA_6_BPC;