Re: [PATCH v9 19/19] media: ti: j721e-csi2rx: Support system suspend using pm_notifier

[Rishikesh Donadkar <r-donadkar@ti.com>]

On 15/01/26 18:20, Tomi Valkeinen wrote:
> Hi,

Hi Tomi,

Thank you for the review.

>
> On 30/12/2025 10:32, Rishikesh Donadkar wrote:
>> From: Jai Luthra <jai.luthra@ideasonboard.com>
>>
>> As this device is the "orchestrator" for the rest of the media
>> pipeline, we need to stop all on-going streams before system suspend and
>> enable them back when the system wakes up from sleep.
>>
>> Using .suspend/.resume callbacks does not work, as the order of those
>> callbacks amongst various devices in the camera pipeline like the sensor,
>> FPD serdes, CSI bridge etc. is impossible to enforce, even with
>> device links. For example, the Cadence CSI bridge is a child device of
>> this device, thus we cannot create a device link with the CSI bridge as
>> a provider and this device as consumer. This can lead to situations
>> where all the dependencies for the bridge have not yet resumed when we
>> request the subdev to start streaming again through the .resume callback
>> defined in this device.
>>
>> Instead here we register a notifier callback with the PM framework
>> which is triggered when the system is fully functional. At this point we
>> can cleanly stop or start the streams, because we know all other devices
>> and their dependencies are functional. A downside of this approach is
>> that the userspace is also alive (not frozen yet, or just thawed), so
>> the suspend notifier might complete before the userspace has completed
>> all ioctls, like QBUF/DQBUF/STREAMON/STREAMOFF.
> It would be good to have at least parts of the explanation here in a
> comment, before the register_pm_notifier() call.

Okay, will add a comment.

Rishikesh

>
>   Tomi
>
>> 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>
>> ---
>>   .../platform/ti/j721e-csi2rx/j721e-csi2rx.c   | 128 ++++++++++++++++++
>>   1 file changed, 128 insertions(+)
>>
>> diff --git a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> index 72da58738e16e..f8e55aa402e0b 100644
>> --- a/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> +++ b/drivers/media/platform/ti/j721e-csi2rx/j721e-csi2rx.c
>> @@ -132,6 +132,7 @@ struct ti_csi2rx_dev {
>>   	struct v4l2_subdev		*source;
>>   	struct v4l2_subdev		subdev;
>>   	struct ti_csi2rx_ctx		ctx[TI_CSI2RX_MAX_CTX];
>> +	struct notifier_block		pm_notifier;
>>   	u8				pix_per_clk;
>>   	/* Buffer to drain stale data from PSI-L endpoint */
>>   	struct {
>> @@ -1539,6 +1540,124 @@ static int ti_csi2rx_runtime_resume(struct device *dev)
>>   	return 0;
>>   }
>>   
>> +static int ti_csi2rx_suspend(struct device *dev)
>> +{
>> +	struct ti_csi2rx_dev *csi = dev_get_drvdata(dev);
>> +	enum ti_csi2rx_dma_state state;
>> +	struct ti_csi2rx_ctx *ctx;
>> +	struct ti_csi2rx_dma *dma;
>> +	unsigned long flags = 0;
>> +	int i, ret = 0;
>> +
>> +	/* If device was not in use we can simply suspend */
>> +	if (pm_runtime_status_suspended(dev))
>> +		return 0;
>> +
>> +	/*
>> +	 * If device is running, assert the pixel reset to cleanly stop any
>> +	 * on-going streams before we suspend.
>> +	 */
>> +	writel(0, csi->shim + SHIM_CNTL);
>> +
>> +	for (i = 0; i < csi->num_ctx; i++) {
>> +		ctx = &csi->ctx[i];
>> +		dma = &ctx->dma;
>> +
>> +		spin_lock_irqsave(&dma->lock, flags);
>> +		state = dma->state;
>> +		spin_unlock_irqrestore(&dma->lock, flags);
>> +
>> +		if (state != TI_CSI2RX_DMA_STOPPED) {
>> +			/* Disable source */
>> +			ret = v4l2_subdev_disable_streams(&csi->subdev,
>> +							  TI_CSI2RX_PAD_FIRST_SOURCE + ctx->idx,
>> +							  BIT(0));
>> +			if (ret)
>> +				dev_err(csi->dev, "Failed to stop subdev stream\n");
>> +		}
>> +
>> +		/* Stop any on-going streams */
>> +		writel(0, csi->shim + SHIM_DMACNTX(ctx->idx));
>> +
>> +		/* Drain DMA */
>> +		ti_csi2rx_drain_dma(ctx);
>> +
>> +		/* Terminate DMA */
>> +		ret = dmaengine_terminate_sync(ctx->dma.chan);
>> +		if (ret)
>> +			dev_err(csi->dev, "Failed to stop DMA\n");
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static int ti_csi2rx_resume(struct device *dev)
>> +{
>> +	struct ti_csi2rx_dev *csi = dev_get_drvdata(dev);
>> +	struct ti_csi2rx_ctx *ctx;
>> +	struct ti_csi2rx_dma *dma;
>> +	struct ti_csi2rx_buffer *buf;
>> +	unsigned long flags = 0;
>> +	unsigned int reg;
>> +	int i, ret = 0;
>> +
>> +	/* If device was not in use, we can simply wakeup */
>> +	if (pm_runtime_status_suspended(dev))
>> +		return 0;
>> +
>> +	/* If device was in use before, restore all the running streams */
>> +	reg = SHIM_CNTL_PIX_RST;
>> +	writel(reg, csi->shim + SHIM_CNTL);
>> +
>> +	for (i = 0; i < csi->num_ctx; i++) {
>> +		ctx = &csi->ctx[i];
>> +		dma = &ctx->dma;
>> +		spin_lock_irqsave(&dma->lock, flags);
>> +		if (dma->state != TI_CSI2RX_DMA_STOPPED) {
>> +			/* Re-submit all previously submitted buffers to DMA */
>> +			list_for_each_entry(buf, &ctx->dma.submitted, list) {
>> +				ti_csi2rx_start_dma(ctx, buf);
>> +			}
>> +			spin_unlock_irqrestore(&dma->lock, flags);
>> +
>> +			/* Restore stream config */
>> +			ti_csi2rx_setup_shim(ctx);
>> +
>> +			ret = v4l2_subdev_enable_streams(&csi->subdev,
>> +							 TI_CSI2RX_PAD_FIRST_SOURCE + ctx->idx,
>> +							 BIT(0));
>> +			if (ret)
>> +				dev_err(ctx->csi->dev, "Failed to start subdev\n");
>> +		} else {
>> +			spin_unlock_irqrestore(&dma->lock, flags);
>> +		}
>> +	}
>> +
>> +	return ret;
>> +}
>> +
>> +static int ti_csi2rx_pm_notifier(struct notifier_block *nb,
>> +				 unsigned long action, void *data)
>> +{
>> +	struct ti_csi2rx_dev *csi =
>> +		container_of(nb, struct ti_csi2rx_dev, pm_notifier);
>> +
>> +	switch (action) {
>> +	case PM_HIBERNATION_PREPARE:
>> +	case PM_SUSPEND_PREPARE:
>> +	case PM_RESTORE_PREPARE:
>> +		ti_csi2rx_suspend(csi->dev);
>> +		break;
>> +	case PM_POST_SUSPEND:
>> +	case PM_POST_HIBERNATION:
>> +	case PM_POST_RESTORE:
>> +		ti_csi2rx_resume(csi->dev);
>> +		break;
>> +	}
>> +
>> +	return NOTIFY_DONE;
>> +}
>> +
>>   static const struct dev_pm_ops ti_csi2rx_pm_ops = {
>>   	RUNTIME_PM_OPS(ti_csi2rx_runtime_suspend, ti_csi2rx_runtime_resume,
>>   		       NULL)
>> @@ -1613,6 +1732,13 @@ static int ti_csi2rx_probe(struct platform_device *pdev)
>>   		goto err_notifier;
>>   	}
>>   
>> +	csi->pm_notifier.notifier_call = ti_csi2rx_pm_notifier;
>> +	ret = register_pm_notifier(&csi->pm_notifier);
>> +	if (ret) {
>> +		dev_err(csi->dev, "Failed to create PM notifier: %d\n", ret);
>> +		goto err_notifier;
>> +	}
>> +
>>   	return 0;
>>   
>>   err_notifier:
>> @@ -1642,6 +1768,8 @@ static void ti_csi2rx_remove(struct platform_device *pdev)
>>   		ti_csi2rx_cleanup_ctx(&csi->ctx[i]);
>>   
>>   	ti_csi2rx_cleanup_notifier(csi);
>> +	unregister_pm_notifier(&csi->pm_notifier);
>> +
>>   	ti_csi2rx_cleanup_v4l2(csi);
>>   	mutex_destroy(&csi->mutex);
>>   	dma_free_coherent(csi->dev, csi->drain.len, csi->drain.vaddr,