Re: [PATCH v2] drm/bridge: waveshare-dsi: Register and attach our DSI device at probe

[Marek Vasut <marek.vasut@mailbox.org>]

On 2/6/26 3:34 PM, Luca Ceresoli wrote:
> Hi Marek,
> 
> On Fri Feb 6, 2026 at 1:57 PM CET, Marek Vasut wrote:
>> In order to avoid any probe ordering issue, the best practice is to move
>> the secondary MIPI-DSI device registration and attachment to the
>> MIPI-DSI host at probe time.
>>
>> Besides solving the probe ordering problems, this makes the bridge work
>> with R-Car DU. The R-Car DU will attempt to locate the DSI host bridge in
>> its own rcar_du_probe()->rcar_du_modeset_init()->rcar_du_encoder_init()
>> by calling of_drm_find_bridge() which calls of_drm_find_and_get_bridge()
>> and iterates over bridge_list to locate the DSI host bridge.
>>
>> However, unless the WS driver calls mipi_dsi_attach() in probe(), the
>> DSI host bridge .attach callback rcar_mipi_dsi_host_attach() is not
>> called and the DSI host bridge is not added into bridge_list. Therefore
>> the of_drm_find_and_get_bridge() called from du_probe() will never find
>> the DSI host bridge and probe will indefinitelly fail with -EPROBE_DEFER.
>>
>> The circular dependency here is, that if rcar_du_encoder_init() would
>> manage to find the DSI host bridge, it would call the WS driver .attach
>> callback ws_bridge_bridge_attach(), but this is too late and can never
>> happen. This change avoids the circular dependency.
>>
>> Reviewed-by: Luca Ceresoli <luca.ceresoli@bootlin.com>
>> Signed-off-by: Marek Vasut <marek.vasut+renesas@mailbox.org>
> 
> Thanks for the very clear description! R-by confirmed.
Can this be applied now ?