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Message-ID: <032b441e-eefc-4574-bf7a-5c4d09599925@ideasonboard.com>
Date: Mon, 1 Dec 2025 15:22:36 +0200
From: Tomi Valkeinen <tomi.valkeinen@...asonboard.com>
To: Rishikesh Donadkar <r-donadkar@...com>, jai.luthra@...ux.dev,
laurent.pinchart@...asonboard.com, mripard@...nel.org
Cc: y-abhilashchandra@...com, devarsht@...com, s-jain1@...com,
vigneshr@...com, mchehab@...nel.org, robh@...nel.org, krzk+dt@...nel.org,
p.zabel@...gutronix.de, conor+dt@...nel.org, sakari.ailus@...ux.intel.com,
hverkuil-cisco@...all.nl, jai.luthra@...asonboard.com,
changhuang.liang@...rfivetech.com, jack.zhu@...rfivetech.com,
sjoerd@...labora.com, dan.carpenter@...aro.org, hverkuil+cisco@...nel.org,
linux-kernel@...r.kernel.org, linux-media@...r.kernel.org,
devicetree@...r.kernel.org
Subject: Re: [PATCH v8 17/18] media: ti: j721e-csi2rx: Support runtime suspend
Hi,
On 12/11/2025 13:54, Rishikesh Donadkar wrote:
> From: Jai Luthra <jai.luthra@...asonboard.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.
I'm not an expert on the dmaengine, but to me this sounds like a bug in
the dma driver. It just sounds very wrong...
> Tested-by: Rishikesh Donadkar <r-donadkar@...com>
> Reviewed-by: Rishikesh Donadkar <r-donadkar@...com>
> Signed-off-by: Jai Luthra <jai.luthra@...asonboard.com>
> Signed-off-by: Rishikesh Donadkar <r-donadkar@...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))
> + 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++) {
> + ret = ti_csi2rx_init_dma(&csi->ctx[i]);
If runtime_resume always requests the dma channels, is the call to
ti_csi2rx_init_dma() in ti_csi2rx_init_ctx() needed? If not, you could
inline the code from ti_csi2rx_init_dma() to here and also drop the
dma_release_channel() call from ti_csi2rx_cleanup_ctx(), making the flow
more understandable.
> + 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);
> + pm_request_idle(csi->dev);
I always forget what exactly the runtime_pm funcs do. What's the idea
here? If you do something else than the plain standard
pm_runtime_enable(), I think it's good to mention what/why in a comment.
> 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);
> + 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,
> },
> };
>
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