Part Number: AM62P
Hi Apps team,
posting on customer behalv who is working on the bring up of the MIPI-DSI panel on an product with the AM62P using TI Linux 6.12.y. They previously had a working panel driver for the same dislpay on a different SOC, but on the AM62P they observe that the dislpay sporadically remains black after boot. Once the e2e Thread is assigned, I'll send you the files via e-mail. But here is the request:
After making substantial changes to the panel driver and moving the panel DCS initialization into prepare(), we found that prepare-time direct DSI transfers were not reliable on our setup. As a result, the system could start the video pipeline while the panel remained uninitialized, leading to a black screen.
Our current understanding is that it cannot be solved from the display panel driver only.
Our local Cadence-side change does the following:
- cdns_dsi_transfer(): pm_runtime_resume_and_get() -> cdns_dsi_init_link() -> cdns_dsi_hs_init() -> cdns_dsi_wait_for_lane_ready() -> transfer -> pm_runtime_put()
- cdns_dsi_hs_init() now returns int and propagates phy_init(), phy_configure(), and phy_power_on() failures
- PLL lock polling was extended
- atomic_pre_enable() now uses the same link/HS/lane-ready sequence
- runtime suspend powers off the PHY and clears phy_initialized / link_initialized
Without this ordering, the first prepare-time DSI commands did not reliably take effect on our setup, which could leave the panel uninitialized while video still started.
With the above changes and some major panel driver modifications, we were able to mitigate the issue fully.
Could you please advise:
- Does this match a known issue or recommended sequencing in TI Linux 6.12.y for direct transfers before video enabled?
- Do you see any concern or regression risk with this runtime PM / PHY / lane-ready handling?
- If the approach looks correct, would TI prefer us to keep it downstream or send it as a patch series for the TI tree?
Please find our current drivers attached.
I can send the Cadence host-side changes as a patch or with any other method if that is easier to review. And if anything, else is needed from our side feel free to reach me.
Thank you,
Marinus
