Re: [PATCH v2 2/2] media: staging: imx: configure src_mux in csi_start

[Philipp Zabel <p.zabel@pengutronix.de>]

On Fr, 2025-11-07 at 11:34 +0100, Michael Tretter wrote:
> After media_pipeline_start() was called, the media graph is assumed to
> be validated. It won't be validated again if a second stream starts.
> 
> The imx-media-csi driver, however, changes hardware configuration in the
> link_validate() callback. This can result in started streams with
> misconfigured hardware.
> 
> In the concrete example, the ipu2_csi1 is driven by a parallel video
> input. After the media pipeline has been started with this
> configuration, a second stream is configured to use ipu1_csi0 with
> MIPI-CSI input from imx6-mipi-csi2. This may require the reconfiguration
> of ipu1_csi0 with ipu_set_csi_src_mux(). Since the media pipeline is
> already running, link_validate won't be called, and the ipu1_csi0 won't
> be reconfigured. The resulting video is broken, because the ipu1_csi0 is
> misconfigured, but no error is reported.
> 
> Move ipu_set_csi_src_mux from csi_link_validate to csi_start to ensure
> that input to ipu1_csi0 is configured correctly when starting the
> stream. This is a local reconfiguration in ipu1_csi0 and is possible
> while the media pipeline is running.
> 
> Since csi_start() is called with priv->lock already locked,
> csi_set_src() must not lock priv->lock again. Thus, the mutex_lock() is
> dropped.
> 
> Signed-off-by: Michael Tretter <m.tretter@pengutronix.de>
> Fixes: 4a34ec8e470c ("[media] media: imx: Add CSI subdev driver")
> Cc: stable@vger.kernel.org

Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>

regards
Philipp