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charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Hi Cristian, On 26/10/26 22:23, Cristian Ciocaltea wrote: > Hi Lucas, > > On 2026/10/26, Lucas Tanure wrote: >> HDMI 2.0 asks the source to set TMDS_Bit_Clock_Ratio in the sink while >> the TMDS clock is stopped and to start the clock at least 1 ms later. >> vc4 writes the bit, and enables the scrambler, at the end of the enable >> sequence, long after the PHY has started, and clears it before the PHY >> stops. A sink that samples the bit when the clock appears never locks >> a 4K60 signal from a Raspberry Pi 5, while laptops that follow the >> order work on the same sink. >> >> Patch 3 is the fix. Patch 1 is needed on BCM2712, where phy_disable() >> was an empty stub upstream, so the PHY kept running after disable; the >> Raspberry Pi tree has carried this since 2024. Patch 2 fixes a >> pre-existing race in the scrambling work cancel that the fix would >> otherwise make easier to hit. >> >> v1 was tested on a Raspberry Pi 5 running the Raspberry Pi 6.18 kernel >> with the same change applied, against the sink that showed the >> problem: plain enable at 4K60, 1080p60 to 4K60, 4K30 to 4K60, a sink >> reset and a sink power cycle all lock with zero character errors. v2 >> and v3 carry the same code; the hardware test of the final form is >> still pending and will be reported in this thread. Mainline was not >> booted on the Pi 5. The BCM2711 path is unchanged except for the >> enable order; I have no Pi 4 at hand. > > While converting vc4 to the common HDMI 2.0 scrambling infrastructure, I > ran several tests on the Raspberry Pi 5 and didn't notice any (obvious) > issues. > > Hence, could you please verify whether your problem reproduces with a > recent mainline kernel? If it does, could you also give [1] a try and > report back the actual behavior? > I suspect you didn't hit this on mainline because vc6_hdmi_phy_disable() is a stub, so the TMDS clock never stops between disable and enable. Best regards, - Maíra > [1] https://lore.kernel.org/lkml/20261014-vc4-common-scramb-v3-0-c68d58d959a2@collabora.com/ > > Regards, > Cristian