drm/i915: set DP Main Stream Attribute for color range on DDI platforms
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 dae84799 ("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 55bc60db ("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: NMichał Kopeć <mkopec12@gmail.com> Reported-by: NN. W. <nw9165-3201@yahoo.com> Reported-by: NNicholas Stommel <nicholas.stommel@gmail.com> Reported-by: NTom Yan <tom.ty89@gmail.com> Tested-by: NNicholas 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+ Reviewed-by: NRodrigo Vivi <rodrigo.vivi@intel.com> Signed-off-by: NJani Nikula <jani.nikula@intel.com> Link: https://patchwork.freedesktop.org/patch/msgid/20180814060001.18224-1-jani.nikula@intel.com
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