Hi Am 27.02.24 um 23:40 schrieb Dmitry Baryshkov:
Hello, We are currently looking at checking and/or possibly redesigning the way the MSM DRM driver handles the HPD events and link training. After a quick glance at the drivers implementing DP support, I noticed following main approaches: - Perform link training at the atomic_enable time, don't report failures (mtk, analogix, zynqmp, tegra, nouveau) - Perform link training at the atomic_enable time, report errors using link_status property (i915, mhdp8546) - Perform link training on the plug event (msm, it8605). - Perform link training from the DPMS handler, also calling it from the enable callback (AMDGPU, radeon). It looks like the majority wins and we should move HPD to atomic_enable time. Is that assumption correct?
Did you ever receive an answer to this question? I currently investigate ast's DP code, which does link training as part of detecting the connector state (in detect_ctx). But most other drivers do this in atomic_enable. I wonder if ast should follow.
Best regards Thomas
Also two related questions: - Is there a plan to actually make use of the link_status property? Intel presented it at FOSDEM 2018, but since that time it was not picked up by other drivers. - Is there any plan to create generic DP link training helpers? After glancing through the DP drivers there is a lot of similar code in the link training functions, with minor differences here and there. And it's those minor differences that bug me. It means that drivers might respond differently to similar devices. Or that there might be minor bugs here and there.
-- -- Thomas Zimmermann Graphics Driver Developer SUSE Software Solutions Germany GmbH Frankenstrasse 146, 90461 Nuernberg, Germany GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman HRB 36809 (AG Nuernberg)
