On Wed, Jun 25, 2025 at 11:18:03AM +0300, Jani Nikula wrote: > On Tue, 24 Jun 2025, Ville Syrjälä <[email protected]> wrote: > > On Tue, Jun 24, 2025 at 10:10:53AM +0530, Nautiyal, Ankit K wrote: > >> > >> On 6/23/2025 8:12 PM, Ville Syrjälä wrote: > >> > On Fri, Jun 20, 2025 at 06:14:16PM +0530, Ankit Nautiyal wrote: > >> >> This reverts commit 584cf613c24a4250d9be4819efc841aa2624d5b6. > >> >> Commit 584cf613c24a ("drm/i915/dp: Reject HBR3 when sink doesn't support > >> >> TPS4") introduced a blanket rejection of HBR3 link rate when the sink > >> >> does > >> >> not support TPS4. While this was intended to address instability > >> >> observed > >> >> on certain eDP panels [1], the TPS4 requirement is only mandated for > >> >> DPRX > >> >> and not for eDPRX. > >> > I see no exception given for eDP regarding this rule. The only exception > >> > allowed is that eDP can say DPCD_REV=1.4 + TPS4_SUPPORTED=0. So I still > >> > claim that these eDP sinks are violating the spec. > >> > >> Hmm.. Yes the spec allows eDP sinks to report DPCD_REV=1.4 and > >> TPS4_SUPPORTED, so perhaps eDPs claiming HBR3 with DPCD rev other than > >> rev 1.4 and not supporting TPS4 are indeed violating the spec. > >> > >> Would it make sense to add a condition that checks for DPCD_REV=1.4. > >> > >> Specifically: > >> > >> if DPCD_REV=1.4 and TPS4_SUPPORTED = 0, then do not prune the HBR3 rate? > >> > >> Or otherway if DPCD_REV!=1.4 and TPS4_SUPPORTER = 0, prune the HBR3 rate > >> > >> This way the patch need not be reverted, but modified to address > >> instability issues for eDP panels that are not aligned with the spec. > >> > >> That said, the gitlab issue#5969 [1] will still need another solution > >> since it seems to have DPCD rev 14 as per logs: > >> > >> DPCD: 14 1e 44 41 00 00 01 80 02 00 02 00 00 0b 80 > > > > I think we do need the quirk. But the commit message should IMO be > > adjusted so that it doesn't claim that these panels are 100% legal. > > Right. But are you okay with reverting 584cf613c24a ("drm/i915/dp: > Reject HBR3 when sink doesn't support TPS4") i.e. allowing HBR3 > *without* TPS4 by default, and quirking the panel that can't handle > HBR3?
Yeah, I think the revert+quirk for the one known bad system is the way to go. > > No matter what the spec says, this seems to be common. More regressing > systems are cropping up, e.g. [1]. > > > BR, > Jani. > > > [1] https://gitlab.freedesktop.org/drm/i915/kernel/-/issues/14517 > > > > > -- > Jani Nikula, Intel -- Ville Syrjälä Intel
