media: staging: imx: configure src_mux in csi_start

media: staging: imx: configure src_mux in csi_start

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: Frank Li <Frank.Li@nxp.com>
Reviewed-by: Philipp Zabel <p.zabel@pengutronix.de>
Signed-off-by: Frank Li <Frank.Li@nxp.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>