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Date:   Fri, 12 May 2023 12:20:12 +0300
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Subject: Re: [PATCH v6 0/8] drm/tidss: Use new connector model for tidss
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To:     Aradhya Bhatia <a-bhatia1@ti.com>, Jyri Sarha <jyri.sarha@iki.fi>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
        Andrzej Hajda <andrzej.hajda@intel.com>,
        Neil Armstrong <neil.armstrong@linaro.org>,
        Robert Foss <rfoss@kernel.org>,
        Jonas Karlman <jonas@kwiboo.se>,
        Jernej Skrabec <jernej.skrabec@gmail.com>,
        Rahul T R <r-ravikumar@ti.com>,
        Swapnil Jakhade <sjakhade@cadence.com>,
        Boris Brezillon <boris.brezillon@collabora.com>,
        Francesco Dolcini <francesco@dolcini.it>
Cc:     DRI Development List <dri-devel@lists.freedesktop.org>,
        Linux Kernel List <linux-kernel@vger.kernel.org>,
        Nishanth Menon <nm@ti.com>,
        Vignesh Raghavendra <vigneshr@ti.com>,
        Devarsh Thakkar <devarsht@ti.com>,
        Jayesh Choudhary <j-choudhary@ti.com>
References: <20230509093036.3303-1-a-bhatia1@ti.com>
From:   Tomi Valkeinen <tomi.valkeinen@ideasonboard.com>
In-Reply-To: <20230509093036.3303-1-a-bhatia1@ti.com>
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On 09/05/2023 12:30, Aradhya Bhatia wrote:
> Hi all,
> 
> I have picked up this long standing series from Nikhil Devshatwar[1].
> 
> This series moves the tidss to using new connectoe model, where the SoC
> driver (tidss) creates the connector and all the bridges are attached
> with the flag DRM_BRIDGE_ATTACH_NO_CONNECTOR. It also now creates bridge
> to support format negotiation and and 'simple' encoder to expose it to
> the userspace.
> 
> Since the bridges do not create the connector, the bus_format and
> bus_flag is set via atomic hooks.
> 
> Support format negotiations in the tfp410, sii902x and mhdp-8546 bridge
> drivers as a first step before moving the connector model.
> 
> These patches were tested on AM625-SK EVM, AM625 SoC based BeaglePlay,
> and J721E-SK. Display support for AM625 SoC has not been added upstream
> and is a WIP. To test this series on AM625 based platforms, basic
> display support patches, (for driver + devicetree), can be found in
> the "next_AttachNoConn" branch on my github fork[2].

Not exactly related to this series, but I was testing this with J7 EVM 
and a Dell DP monitor.

I'm seeing DPCD errors quite often, which also sometimes cause link 
training errors. E.g.:

cdns-mhdp8546 a000000.dp-bridge: Failed to read DPCD addr 0

cdns-mhdp8546 a000000.dp-bridge: Failed to adjust Link Training.

I tested retrying the read/write when it fails, and that seemed to help 
a bit, but not always. Are you using the firmware that's on the upstream 
linux-firmware repo?

  Tomi