Re: [PATCH 0/3] media: imx8mq-mipi-csi2: Simplify power management handling

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

On Mon, Sep 30, 2024 at 07:08:09AM +0000, G.N. Zhou (OSS) wrote:
> On Sunday, September 29, 2024 9:44 PM, Laurent Pinchart wrote:
> > 
> > Hello,
> > 
> > This small patch series is a reaction to "[PATCH] media: nxp:
> > imx8mq-mipi-csi2: Fix CSI clocks always enabled issue" ([1]). Instead of making
> > the PM handling more complex, I think it can be greatly simplified.
> > 
> > I have only compile-tested the patches. Guoniu, could you give this a try ?
> 
> After applying the patches and test both on iMX8ULP.
> 
> For iMX8ULP, it will cause kernel dump when access CSI registers and
> system hang during do suspend/resume while streaming
> Need to add system suspend/resume handlers and call
> pm_runtime_force_suspend/resume in the handlers.
> 
> I tried to debug this issue and found pm runtime callback won't be
> called when system resume. The state of power domain won't enabled.

Thank you for testing.

I wonder if this could be caused by the CSI bridge being resumed from
system sleep before the CSI-2 receiver. Could you check if that's the
case ? If so, does the following change fix the issue ?

diff --git a/drivers/media/platform/nxp/imx7-media-csi.c b/drivers/media/platform/nxp/imx7-media-csi.c
index 9566ff738818..c66b0621e395 100644
--- a/drivers/media/platform/nxp/imx7-media-csi.c
+++ b/drivers/media/platform/nxp/imx7-media-csi.c
@@ -2057,9 +2057,22 @@ static int imx7_csi_notify_bound(struct v4l2_async_notifier *notifier,
 {
 	struct imx7_csi *csi = imx7_csi_notifier_to_dev(notifier);
 	struct media_pad *sink = &csi->sd.entity.pads[IMX7_CSI_PAD_SINK];
+	struct device_link *link;
 
 	csi->src_sd = sd;
 
+	/*
+	 * Enforce suspend/resume ordering between the source (supplier) and
+	 * the CSI (consumer). The source will be suspended before and resume
+	 * after the CSI.
+	 */
+	link = device_link_add(csi->dev, sd->dev, DL_FLAG_STATELESS);
+	if (!link) {
+		dev_err(csi->dev,
+			"Failed to create device link to source %s\n", sd->name);
+		return -EINVAL;
+	}
+
 	return v4l2_create_fwnode_links_to_pad(sd, sink, MEDIA_LNK_FL_ENABLED |
 					       MEDIA_LNK_FL_IMMUTABLE);
 }

> > [1] https://lore.kernel.org/r/20240929101635.1648234-1-guoniu.zhou@oss.nxp.com
> > 
> > Laurent Pinchart (3):
> >   media: imx8mq-mipi-csi2: Drop stream stop/restart at suspend/resume
> >     time
> >   media: imx8mq-mipi-csi2: Drop ST_SUSPENDED guard
> >   media: imx8mq-mipi-csi2: Drop system suspend/resume handlers
> > 
> >  drivers/media/platform/nxp/imx8mq-mipi-csi2.c | 113 ++----------------
> >  1 file changed, 10 insertions(+), 103 deletions(-)
> > 
> > 
> > base-commit: 81ee62e8d09ee3c7107d11c8bbfd64073ab601ad

-- 
Regards,

Laurent Pinchart