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

Message ID 20240929134354.20735-1-laurent.pinchart@ideasonboard.com (mailing list archive)
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Series media: imx8mq-mipi-csi2: Simplify power management handling | expand

Message

Laurent Pinchart Sept. 29, 2024, 1:43 p.m. UTC 
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 ?

[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

Comments

G.N. Zhou (OSS) Sept. 30, 2024, 7:08 a.m. UTC | #1 
Hi Laurent,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: Sunday, September 29, 2024 9:44 PM
> To: rmfrfs@gmail.com; martink@posteo.de; kernel@puri.sm;
> mchehab@kernel.org; shawnguo@kernel.org; s.hauer@pengutronix.de;
> kernel@pengutronix.de; festevam@gmail.com
> Cc: G.N. Zhou (OSS) <guoniu.zhou@oss.nxp.com>; imx@lists.linux.dev; linux-
> media@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org
> Subject: [PATCH 0/3] media: imx8mq-mipi-csi2: Simplify power management
> handling
> 
> 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.

> 
> [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
Laurent Pinchart Sept. 30, 2024, 7:21 a.m. UTC | #2 
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
G.N. Zhou (OSS) Sept. 30, 2024, 7:51 a.m. UTC | #3 
Hi Laurent,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: Monday, September 30, 2024 3:22 PM
> To: G.N. Zhou (OSS) <guoniu.zhou@oss.nxp.com>
> Cc: rmfrfs@gmail.com; martink@posteo.de; kernel@puri.sm;
> mchehab@kernel.org; shawnguo@kernel.org; s.hauer@pengutronix.de;
> kernel@pengutronix.de; festevam@gmail.com; imx@lists.linux.dev; linux-
> media@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH 0/3] media: imx8mq-mipi-csi2: Simplify power management
> handling
> 
> 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 ?

I tested on iMX8ULP which don't use CSI bridge but ISI, not iMX8MQ. In ISI driver, I notice that
it already handler the device relationship when subdev bound like bellow:

link = device_link_add(isi->dev, sd->dev, DL_FLAG_STATELESS);
if (!link) {
        dev_err(isi->dev,
                "Failed to create device link to source %s\n", sd->name);
        return -EINVAL;
}

For iMX8MQ, I'm trying to enable it, but meet some problems, so can't give you the results in short time.

> 
> 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.n
> > > xp.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
Martin Kepplinger-Novakovic Oct. 7, 2024, 10:44 a.m. UTC | #4 
Am Montag, dem 30.09.2024 um 10:21 +0300 schrieb Laurent Pinchart:
> 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);
>  }


hi Laurent,

I now tested your 3 patches, initially including this extra change, on
the imx8mq Librem 5 and indeed streaming continues after system resume
now. It works without this extra change too, even though it seems to
make sense.

so for the 3-patch series at least:

Tested-by: Martin Kepplinger-Novaković <martink@posteo.de>

thanks. I seem to be able to drop a few patches now, but if anyone else
can test it too, please wait for that as well,

                              martin
Laurent Pinchart Oct. 7, 2024, 9:43 p.m. UTC | #5 
Hi Guo,

On Mon, Sep 30, 2024 at 07:51:45AM +0000, G.N. Zhou (OSS) wrote:
> On Monday, September 30, 2024 3:22 PM, Laurent Pinchart wrote:
> > 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 ?
> 
> I tested on iMX8ULP which don't use CSI bridge but ISI, not iMX8MQ. In ISI driver, I notice that
> it already handler the device relationship when subdev bound like bellow:
> 
> link = device_link_add(isi->dev, sd->dev, DL_FLAG_STATELESS);
> if (!link) {
>         dev_err(isi->dev,
>                 "Failed to create device link to source %s\n", sd->name);
>         return -EINVAL;
> }

Ah yes indeed with the ISI it should already be handled.

I can't test this on hardware now as I'm travelling. Is the system hang
happening at suspend or resume time ? What is the order of the
suspend/resume handlers calls for the imx8-isi driver and the
imx8mq-mipi-csi2 driver ?

> For iMX8MQ, I'm trying to enable it, but meet some problems, so can't
> give you the results in short time.
> 
> > 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
G.N. Zhou (OSS) Oct. 9, 2024, 8:30 a.m. UTC | #6 
Hi Laruent,

> -----Original Message-----
> From: Laurent Pinchart <laurent.pinchart@ideasonboard.com>
> Sent: Tuesday, October 8, 2024 5:44 AM
> To: G.N. Zhou (OSS) <guoniu.zhou@oss.nxp.com>
> Cc: rmfrfs@gmail.com; martink@posteo.de; kernel@puri.sm;
> mchehab@kernel.org; shawnguo@kernel.org; s.hauer@pengutronix.de;
> kernel@pengutronix.de; festevam@gmail.com; imx@lists.linux.dev; linux-
> media@vger.kernel.org; linux-arm-kernel@lists.infradead.org; linux-
> kernel@vger.kernel.org
> Subject: Re: [PATCH 0/3] media: imx8mq-mipi-csi2: Simplify power
> management handling
> 
> Hi Guo,
> 
> On Mon, Sep 30, 2024 at 07:51:45AM +0000, G.N. Zhou (OSS) wrote:
> > On Monday, September 30, 2024 3:22 PM, Laurent Pinchart wrote:
> > > 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 ?
> >
> > I tested on iMX8ULP which don't use CSI bridge but ISI, not iMX8MQ. In
> > ISI driver, I notice that it already handler the device relationship when subdev
> bound like bellow:
> >
> > link = device_link_add(isi->dev, sd->dev, DL_FLAG_STATELESS); if
> > (!link) {
> >         dev_err(isi->dev,
> >                 "Failed to create device link to source %s\n", sd->name);
> >         return -EINVAL;
> > }
> 
> Ah yes indeed with the ISI it should already be handled.
> 
> I can't test this on hardware now as I'm travelling. Is the system hang happening
> at suspend or resume time ? What is the order of the suspend/resume handlers
> calls for the imx8-isi driver and the
> imx8mq-mipi-csi2 driver ?

#1) Is the system hang happening at suspend or resume time ?
       After applying your patches, system hang will happened at resume time. Adding
       log and enable no_console_suspend, I can know the the point of causing issue is
       accessing CSI registers when top-level(ISI) device try to enable stream from CSI in
       ISI resume callback like bellow:
       mxc_isi_pm_resume(dev)
           mxc_isi_video_resume(pipe)
               mxc_isi_pipe_enable(pipe)
                   v4l2_subdev_enable_streams(...)       
                        mx8mq_mipi_csi_s_stream()
                            imx8mq_mipi_csi_start_stream()
                                imx8mq_mipi_csi_set_params(state)
                                    imx8mq_mipi_csi_write(state, CSI2RX_CFG_NUM_LANES, lanes - 1);      <---   causing kernel panic and system don't have any response

#2) What is the order of the suspend/resume handlers calls for the imx8-isi driver and the
       imx8mq-mipi-csi2 driver ?
       Suspend: ISI -> CSI
       Resume: CSI -> ISI

One more thing when I debugging this issue that the value of CSI device "power.usage_count" in two cases

Case 1: Don't do system suspend/resume and only run camera test.
              Top-level device(ISI) can call CSI s_stream when start/stop capture and CSI runtime_suspend/resume will
              be called in this case since the value of CSI device power.usage_count is 1

Case 2: Run camera test first and keep it run in backend, then run system suspend/resume.
              Top-level device(ISI) will CSI s_stream() to start capture when run camera test and then, ISI system suspend
              callback will disable stream from CSI by calling s_stream(), the pm_runtime_put(dev) doesn't call CSI runtime
              suspend callback since the value of CSI device power.usage_count is 2.

I'm not sure if it's helpfull, just for your reference.       

> 
> > For iMX8MQ, I'm trying to enable it, but meet some problems, so can't
> > give you the results in short time.
> >
> > > 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@o
> > > > > ss.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