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HDMI 2.0 section 6.1.3.1 specifies that after enabling Scrambling_Enable and starting scrambled video transmission, the source should poll Scrambling_Status until it reads 1 or until a timeout of 200 ms expires. Add a polling step after enabling the HDMI port to check the scrambling status when HDMI scrambling is enabled. On some HDMI 2.0 sinks, omitting this check can result in 4K@60Hz (594 MHz) failing to come up correctly because the sink has not yet finished its scrambling setup. In practice, waiting for the scrambling status here fixes such sinks. While this synchronous polling is not itself explicitly required for correct modeset sequencing, HDMI 2.0 section 6.1.3.1 does recommend it as the way for the source to verify that the TMDS link is functioning correctly with scrambling enabled. v3: - Add explicit HDMI 2.0 section reference in code comment - Clarify commit message around the observed sink fix v2: - Poll TMDS_Scrambler_Status for up to 200 ms instead of using a fixed delay Reported-by: Jerome Tollet <jtollet@cisco.com> Closes: https://gitlab.freedesktop.org/drm/xe/kernel/-/issues/6868 Link: https://lore.kernel.org/dri-devel/20251230091037.5603-1-jerome.tollet@gmail.com/ Signed-off-by: Jerome Tollet <jerome.tollet@gmail.com> Signed-off-by: Ankit Nautiyal <ankit.k.nautiyal@intel.com> Reviewed-by: Arun R Murthy <arun.r.murthy@intel.com> Link: https://patch.msgid.link/20260520022544.3097252-1-ankit.k.nautiyal@intel.com