linux-kernel - Re: [PATCH] media: nxp: imx8mq-mipi-csi2: Fix CSI clocks always enabled issue

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Message-ID: <20240929120051.GA31662@pendragon.ideasonboard.com>
Date: Sun, 29 Sep 2024 15:00:51 +0300
From: Laurent Pinchart <laurent.pinchart@...asonboard.com>
To: guoniu.zhou@....nxp.com
Cc: rmfrfs@...il.com, martink@...teo.de, kernel@...i.sm, mchehab@...nel.org,
	shawnguo@...nel.org, s.hauer@...gutronix.de, kernel@...gutronix.de,
	festevam@...il.com, imx@...ts.linux.dev,
	linux-media@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] media: nxp: imx8mq-mipi-csi2: Fix CSI clocks always
 enabled issue

Hi Guoniu,

Thank you for the patch.

On Sun, Sep 29, 2024 at 06:16:35PM +0800, guoniu.zhou@....nxp.com wrote:
> From: "Guoniu.zhou" <guoniu.zhou@....com>
> 
> Fix CSI clocks always enabled issue after run system suspend/resume.
> 
> The clocks for CSI will be enabled in imx8mq_mipi_csi_pm_resume()
> when system resume and the state of CSI will be set to ST_POWERED.
> It not only cause clock always enabled issue but also system hang
> issue on iMX8ULP platform since imx8mq_mipi_csi_pm_suspend() will
> access CSI registers if run system suspend/resume again, but the
> CSI power domain is not active.
> 
> In order to fix this issue, using pm_runtime_force_suspend/resume
> instead of calling imx8mq_mipi_csi_pm_suspend/resume directly.

I think you can simplify suspend/resume handling in the driver by
dropping the system suspend/resume handlers. At system suspend time the
device should already be stopped, because the top-level driver (the CSI
bridge in the i.MX8MQ) should have stopped the pipeline. Similarly, at
system resume time, there should be no need to restart streaming, as the
top-level driver will control that.

I'll send a patch and CC you, could you give it a try ?

> Signed-off-by: Guoniu.zhou <guoniu.zhou@....com>
> ---
>  drivers/media/platform/nxp/imx8mq-mipi-csi2.c | 7 +++++--
>  1 file changed, 5 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/nxp/imx8mq-mipi-csi2.c b/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> index d4a6c5532969..15029bb81b35 100644
> --- a/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> +++ b/drivers/media/platform/nxp/imx8mq-mipi-csi2.c
> @@ -697,8 +697,11 @@ static int imx8mq_mipi_csi_suspend(struct device *dev)
>  {
>  	struct v4l2_subdev *sd = dev_get_drvdata(dev);
>  	struct csi_state *state = mipi_sd_to_csi2_state(sd);
> +	int ret;
>  
> -	imx8mq_mipi_csi_pm_suspend(dev);
> +	ret = pm_runtime_force_suspend(dev);
> +	if (ret < 0)
> +		return ret;
>  
>  	state->state |= ST_SUSPENDED;
>  
> @@ -713,7 +716,7 @@ static int imx8mq_mipi_csi_resume(struct device *dev)
>  	if (!(state->state & ST_SUSPENDED))
>  		return 0;
>  
> -	return imx8mq_mipi_csi_pm_resume(dev);
> +	return pm_runtime_force_resume(dev);
>  }
>  
>  static int imx8mq_mipi_csi_runtime_suspend(struct device *dev)

-- 
Regards,

Laurent Pinchart