Re: [PATCH v8 17/18] media: ti: j721e-csi2rx: Support runtime suspend

[Sakari Ailus <sakari.ailus@linux.intel.com>]

Hi Rishikesh,

On Wed, Nov 12, 2025 at 05:24:58PM +0530, Rishikesh Donadkar wrote:
> From: Jai Luthra <jai.luthra@ideasonboard.com>
> 
> Add support for runtime power-management to enable powering off the
> shared power domain between Cadence CSI2RX and TI CSI2RX wrapper when
> the device(s) are not in use.
> 
> When powering off the IP, the PSI-L endpoint loses the paired DMA
> channels. Thus we have to release the DMA channels at runtime suspend
> and request them again at resume.
> 
> Tested-by: Rishikesh Donadkar <r-donadkar@ti.com>
> Reviewed-by: Rishikesh Donadkar <r-donadkar@ti.com>
> Signed-off-by: Jai Luthra <jai.luthra@ideasonboard.com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@ti.com>
> ---
>  drivers/media/platform/ti/Kconfig             |  1 +
>  .../platform/ti/j721e-csi2rx/j721e-csi2rx.c   | 55 ++++++++++++++++++-
>  2 files changed, 54 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/media/platform/ti/Kconfig b/drivers/media/platform/ti/Kconfig
> index 3bc4aa35887e6..a808063e24779 100644
> --- a/drivers/media/platform/ti/Kconfig
> +++ b/drivers/media/platform/ti/Kconfig
> @@ -70,6 +70,7 @@ config VIDEO_TI_J721E_CSI2RX
>  	depends on VIDEO_CADENCE_CSI2RX
>  	depends on PHY_CADENCE_DPHY_RX || COMPILE_TEST
>  	depends on ARCH_K3 || COMPILE_TEST
> +	depends on PM
>  	select VIDEOBUF2_DMA_CONTIG
>  	select V4L2_FWNODE
>  	help
> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> index 528041ee78cf3..21e032c64b901 100644
> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
> @@ -13,6 +13,7 @@
>  #include <linux/module.h>
>  #include <linux/of_platform.h>
>  #include <linux/platform_device.h>
> +#include <linux/pm_runtime.h>
>  #include <linux/property.h>
>  
>  #include <media/cadence/cdns-csi2rx.h>
> @@ -963,12 +964,16 @@ static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	unsigned long flags;
>  	int ret = 0;
>  
> +	ret = pm_runtime_resume_and_get(csi->dev);
> +	if (ret)
> +		return ret;
> +
>  	spin_lock_irqsave(&dma->lock, flags);
>  	if (list_empty(&dma->queue))
>  		ret = -EIO;
>  	spin_unlock_irqrestore(&dma->lock, flags);
>  	if (ret)
> -		return ret;
> +		goto err;
>  
>  	ret = video_device_pipeline_start(&ctx->vdev, &csi->pipe);
>  	if (ret)
> @@ -1024,6 +1029,8 @@ static int ti_csi2rx_start_streaming(struct vb2_queue *vq, unsigned int count)
>  	writel(0, csi->shim + SHIM_DMACNTX(ctx->idx));
>  err:
>  	ti_csi2rx_cleanup_buffers(ctx, VB2_BUF_STATE_QUEUED);
> +	pm_runtime_put(csi->dev);
> +
>  	return ret;
>  }
>  
> @@ -1055,6 +1062,7 @@ static void ti_csi2rx_stop_streaming(struct vb2_queue *vq)
>  
>  	ti_csi2rx_stop_dma(ctx);
>  	ti_csi2rx_cleanup_buffers(ctx, VB2_BUF_STATE_ERROR);
> +	pm_runtime_put(csi->dev);
>  }
>  
>  static const struct vb2_ops csi_vb2_qops = {
> @@ -1261,7 +1269,9 @@ static void ti_csi2rx_cleanup_notifier(struct ti_csi2rx_dev *csi)
>  
>  static void ti_csi2rx_cleanup_ctx(struct ti_csi2rx_ctx *ctx)
>  {
> -	dma_release_channel(ctx->dma.chan);
> +	if (!pm_runtime_status_suspended(ctx->csi->dev))

What's the motivation for this change? Do the DMA channel need to be
released only if the device's RPM status isn't suspended?

Is there a guarantee Runtime PM is disabled when the function is called?
Otherwise there's no guarantee state change couldn't occur.

> +		dma_release_channel(ctx->dma.chan);
> +
>  	vb2_queue_release(&ctx->vidq);
>  
>  	video_unregister_device(&ctx->vdev);
> @@ -1512,6 +1522,39 @@ static int ti_csi2rx_init_ctx(struct ti_csi2rx_ctx *ctx)
>  	return ret;
>  }
>  
> +static int ti_csi2rx_runtime_suspend(struct device *dev)
> +{
> +	struct ti_csi2rx_dev *csi = dev_get_drvdata(dev);
> +	int i;
> +
> +	if (csi->enable_count != 0)
> +		return -EBUSY;
> +
> +	for (i = 0; i < csi->num_ctx; i++)
> +		dma_release_channel(csi->ctx[i].dma.chan);
> +
> +	return 0;
> +}
> +
> +static int ti_csi2rx_runtime_resume(struct device *dev)
> +{
> +	struct ti_csi2rx_dev *csi = dev_get_drvdata(dev);
> +	int ret, i;
> +
> +	for (i = 0; i < csi->num_ctx; i++) {

You could declare i (as unsigned int) here.

The same for ret actually.

> +		ret = ti_csi2rx_init_dma(&csi->ctx[i]);
> +		if (ret)
> +			return ret;
> +	}
> +
> +	return 0;
> +}
> +
> +static const struct dev_pm_ops ti_csi2rx_pm_ops = {
> +	RUNTIME_PM_OPS(ti_csi2rx_runtime_suspend, ti_csi2rx_runtime_resume,
> +		       NULL)
> +};
> +
>  static int ti_csi2rx_probe(struct platform_device *pdev)
>  {
>  	struct device_node *np = pdev->dev.of_node;
> @@ -1579,6 +1622,10 @@ static int ti_csi2rx_probe(struct platform_device *pdev)
>  		goto err_notifier;
>  	}
>  
> +	pm_runtime_set_active(csi->dev);
> +	pm_runtime_enable(csi->dev);

Note that the sub-device driver's UAPI may be already available to users
when the async sub-device is registered. Therefore you'll need enable
runtime PM before that.

> +	pm_request_idle(csi->dev);
> +
>  	return 0;
>  
>  err_notifier:
> @@ -1609,6 +1656,9 @@ static void ti_csi2rx_remove(struct platform_device *pdev)
>  	mutex_destroy(&csi->mutex);
>  	dma_free_coherent(csi->dev, csi->drain.len, csi->drain.vaddr,
>  			  csi->drain.paddr);

Is there a guarantee the device is in a particular runtime PM state here,
e.g. suspended?

> +	pm_runtime_disable(&pdev->dev);
> +	pm_runtime_set_suspended(&pdev->dev);
> +
>  }
>  
>  static const struct of_device_id ti_csi2rx_of_match[] = {
> @@ -1623,6 +1673,7 @@ static struct platform_driver ti_csi2rx_pdrv = {
>  	.driver = {
>  		.name = TI_CSI2RX_MODULE_NAME,
>  		.of_match_table = ti_csi2rx_of_match,
> +		.pm		= &ti_csi2rx_pm_ops,
>  	},
>  };
>  

-- 
Kind regards,

Sakari Ailus