Re: [PATCH 1/2] drm: bridge: samsung-dsim: Initialize bridge on attach

[Marek Vasut <marex@denx.de>]

On 5/13/24 9:57 AM, Marek Szyprowski wrote:
> 
> On 13.05.2024 04:16, Marek Vasut wrote:
>> Initialize the bridge on attach already, to force lanes into LP11
>> state, since attach does trigger attach of downstream bridges which
>> may trigger (e)DP AUX channel mode read.
>>
>> This fixes a corner case where DSIM with TC9595 attached to it fails
>> to operate the DP AUX channel, because the TC9595 enters some debug
>> mode when it is released from reset without lanes in LP11 mode. By
>> ensuring the DSIM lanes are in LP11, the TC9595 (tc358767.c driver)
>> can be reset in its attach callback called from DSIM attach callback,
>> and recovered out of the debug mode just before TC9595 performs first
>> AUX channel access later in its attach callback.
>>
>> Signed-off-by: Marek Vasut <marex@denx.de>
> 
> This patch breaks driver operation on Samsung TM2e board with S6E3HF2
> DSI panel. The initialization procedure is very fragile and it looks
> that the changes must be done very carefully. We discussed this many
> times when converting this driver from Exynos DSI to generic Samsung DSI
> used on IMX and other SoCs.

Clearly we need to find a way to support both use cases .

What options do we have ?

Does the panel require DSI lanes in some specific state when it is 
released from reset ?