linux-kernel - Re: [PATCH v2 0/2] drm/bridge: tc358767: Fix DRM_BRIDGE_ATTACH_NO

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Message-ID: <5afdf107-9063-4eec-a88c-0ca3e722e0bc@ideasonboard.com>
Date:   Wed, 8 Nov 2023 15:06:41 +0200
From:   Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To:     Alexander Stein <alexander.stein@...tq-group.com>,
        Aradhya Bhatia <a-bhatia1@...com>,
        Jan Kiszka <jan.kiszka@...mens.com>,
        Andrzej Hajda <andrzej.hajda@...el.com>,
        Neil Armstrong <neil.armstrong@...aro.org>,
        Robert Foss <rfoss@...nel.org>,
        Laurent Pinchart <Laurent.pinchart@...asonboard.com>,
        Jonas Karlman <jonas@...boo.se>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
        Maxime Ripard <mripard@...nel.org>,
        Thomas Zimmermann <tzimmermann@...e.de>,
        David Airlie <airlied@...il.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Sam Ravnborg <sam@...nborg.org>,
        dri-devel@...ts.freedesktop.org
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] drm/bridge: tc358767: Fix
 DRM_BRIDGE_ATTACH_NO_CONNECTOR case

On 08/11/2023 14:45, Alexander Stein wrote:
> Hi Tomi,
> 
> Am Mittwoch, 8. November 2023, 12:27:21 CET schrieb Tomi Valkeinen:
>> These two patches are needed to make tc358767 work in the
>> DRM_BRIDGE_ATTACH_NO_CONNECTOR case, at least when using a DP connector.
>>
>> I have tested this with TI AM654 EVM with a tc358767 add-on card
>> connected to a DP monitor.
> 
> Just a question regarding the usage of this DSI-DP bridge.
> What is the state of the DSI lanes after the DSI host has been initialized,
> but before calling atomic_pre_enable? AFAIK this bridge requires LP-11 on DSI
> at any time for accessing the AUX channel.

Good question. I don't know, as we use it in DPI mode (DPI-DP bridge). I 
guess the DSI state is undefined, as it might well be that the DSI host 
driver's (pre-)enable is the place where the DSI is powered up and 
initialized.

So you think in DSI mode this might fail, as AUX (possibly) won't work 
when calling tc_get_edid()? We could add a check there, and skip the 
tc_get_display_props() if in DSI mode. But tc_get_edid() surely won't 
work then.

It would be good if someone with a board where tc358767 is used in DSI 
mode could test this. But, of course, it'll only be testing that 
particular DSI host behavior...

  Tomi

> 
> Best regards,
> Alexander
> 
>> Signed-off-by: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
>> ---
>> Changes in v2:
>> - Update the format negotiation patch as discussed in
>> https://lore.kernel.org/all/7ddf0edb-2925-4b7c-ad07-27c030dd0232@ti.com/ -
>> Link to v1:
>> https://lore.kernel.org/r/20231031-tc358767-v1-0-392081ad9f4b@ideasonboard.
>> com
>>
>> ---
>> Aradhya Bhatia (1):
>>        drm/bridge: tc358767: Add format negotiation hooks for DPI/DSI to
>> (e)DP
>>
>> Tomi Valkeinen (1):
>>        drm/bridge: tc358767: Fix link properties discovery
>>
>>   drivers/gpu/drm/bridge/tc358767.c | 32 ++++++++++++++++++++++++++++++++
>>   1 file changed, 32 insertions(+)
>> ---
>> base-commit: 9d7c8c066916f231ca0ed4e4fce6c4b58ca3e451
>> change-id: 20231031-tc358767-58e3ebdf95f0
>>
>> Best regards,
> 
>