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

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Date:   Mon, 11 Dec 2023 09:42:37 +0100
From:   Alexander Stein <alexander.stein@...tq-group.com>
To:     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,
        Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
Cc:     linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] drm/bridge: tc358767: Fix DRM_BRIDGE_ATTACH_NO_CONNECTOR case

Hi Tomi,

Am Mittwoch, 6. Dezember 2023, 13:11:59 CET schrieb Tomi Valkeinen:
> Hi,
> 
> 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.
> 
> We haven't received any test reports for the DSI-DP case... I was
> looking at the datasheet, and I wonder, why do you say the bridge
> requires DSI to be up for the AUX transactions?

Looking at Figure 4.20 (Power On Sequence) in the datasheet TC9595XBG (Rev 1.1 
2021-06-23) you can see that RESX can be released (only) after DSI lanes went 
to LP-11 state. I got information, down from the support, that LP-11 must be 
up in order to use AUX channel. This also matches our observations, DSI hosts 
often enable LP-11 only in atomic_prepare. That's too late so we used some 
hacks to enable LP-11 right from the beginning just to get access to AUX 
channel.

Best regards
Alexander

> 
>   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@ideasonboar
> >> d.
> >> 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,


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