Michael Walle ff3d5d04db drm: bridge: samsung-dsim: Don't use FORCE_STOP_STATE ... The FORCE_STOP_STATE bit is unsuitable to force the DSI link into LP-11 mode. It seems the bridge internally queues DSI packets and when the FORCE_STOP_STATE bit is cleared, they are sent in close succession without any useful timing (this also means that the DSI lanes won't go into LP-11 mode). The length of this gibberish varies between 1ms and 5ms. This sometimes breaks an attached bridge (TI SN65DSI84 in this case). In our case, the bridge will fail in about 1 per 500 reboots. The FORCE_STOP_STATE handling was introduced to have the DSI lanes in LP-11 state during the .pre_enable phase. But as it turns out, none of this is needed at all. Between samsung_dsim_init() and samsung_dsim_set_display_enable() the lanes are already in LP-11 mode. The code as it was before commit 20c827683d ("drm: bridge: samsung-dsim: Fix init during host transfer") and 0c14d31306 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") was correct in this regard. This patch basically reverts both commits. It was tested on an i.MX8M SoC with an SN65DSI84 bridge. The signals were probed and the DSI packets were decoded during initialization and link start-up. After this patch the first DSI packet on the link is a VSYNC packet and the timing is correct. Command mode between .pre_enable and .enable was also briefly tested by a quick hack. There was no DSI link partner which would have responded, but it was made sure the DSI packet was send on the link. As a side note, the command mode seems to just work in HS mode. I couldn't find that the bridge will handle commands in LP mode. Fixes: 20c827683d ("drm: bridge: samsung-dsim: Fix init during host transfer") Fixes: 0c14d31306 ("drm: bridge: samsung-dsim: Fix i.MX8M enable flow to meet spec") Signed-off-by: Michael Walle <mwalle@kernel.org> Signed-off-by: Inki Dae <inki.dae@samsung.com> Link: https://patchwork.freedesktop.org/patch/msgid/20231113164344.1612602-1-mwalle@kernel.org		2024-01-26 22:48:47 +09:00
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drm	drm: bridge: samsung-dsim: Don't use FORCE_STOP_STATE	2024-01-26 22:48:47 +09:00
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