linux-kernel - Re: [PATCH v2] media: xilinx: Use dma_request_chan() instead dma_request_slave

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Date:   Thu, 16 Jan 2020 12:36:18 +0100
From:   Hans Verkuil <hverkuil@...all.nl>
To:     Laurent Pinchart <laurent.pinchart@...asonboard.com>,
        Peter Ujfalusi <peter.ujfalusi@...com>
Cc:     mchehab@...nel.org, hyun.kwon@...inx.com, vkoul@...nel.org,
        linux-media@...r.kernel.org, linux-kernel@...r.kernel.org,
        michal.simek@...inx.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2] media: xilinx: Use dma_request_chan() instead
 dma_request_slave_channel()

On 1/15/20 6:28 PM, Laurent Pinchart wrote:
> Hi Peter,
> 
> (CC'ing Hans)
> 
> Thank you for the patch.
> 
> On Fri, Jan 10, 2020 at 09:16:48AM +0200, Peter Ujfalusi wrote:
>> dma_request_slave_channel() is a wrapper on top of dma_request_chan()
>> eating up the error code.
>>
>> By using dma_request_chan() directly the driver can support deferred
>> probing against DMA.
>>
>> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@...com>
> 
> Reviewed-by: Laurent Pinchart <laurent.pinchart@...asonboard.com>
> 
> and taken in my tree. Hans, you asked me on IRC to review this, did you
> plan to get it merged upstream yourself ? If so I'll drop it.

Yes, I'll take it. I have similar patches as well in my upcoming PR, so
it makes sense to combine them.

Thanks for reviewing this!

	Hans

> 
>> ---
>> Hi,
>>
>> Changes since v1:
>> - Fix cleanup path when DMA request failed as suggested by Laurent
>> - Print error only in case when the error is not EPROBE_DEFER
>>
>>  drivers/media/platform/xilinx/xilinx-dma.c | 11 ++++++-----
>>  1 file changed, 6 insertions(+), 5 deletions(-)
>>
>> diff --git a/drivers/media/platform/xilinx/xilinx-dma.c b/drivers/media/platform/xilinx/xilinx-dma.c
>> index b211380a11f2..3bb54a4db6a4 100644
>> --- a/drivers/media/platform/xilinx/xilinx-dma.c
>> +++ b/drivers/media/platform/xilinx/xilinx-dma.c
>> @@ -725,10 +725,11 @@ int xvip_dma_init(struct xvip_composite_device *xdev, struct xvip_dma *dma,
>>  
>>  	/* ... and the DMA channel. */
>>  	snprintf(name, sizeof(name), "port%u", port);
>> -	dma->dma = dma_request_slave_channel(dma->xdev->dev, name);
>> -	if (dma->dma == NULL) {
>> -		dev_err(dma->xdev->dev, "no VDMA channel found\n");
>> -		ret = -ENODEV;
>> +	dma->dma = dma_request_chan(dma->xdev->dev, name);
>> +	if (IS_ERR(dma->dma)) {
>> +		ret = PTR_ERR(dma->dma);
>> +		if (ret != -EPROBE_DEFER)
>> +			dev_err(dma->xdev->dev, "no VDMA channel found\n");
>>  		goto error;
>>  	}
>>  
>> @@ -752,7 +753,7 @@ void xvip_dma_cleanup(struct xvip_dma *dma)
>>  	if (video_is_registered(&dma->video))
>>  		video_unregister_device(&dma->video);
>>  
>> -	if (dma->dma)
>> +	if (!IS_ERR_OR_NULL(dma->dma))
>>  		dma_release_channel(dma->dma);
>>  
>>  	media_entity_cleanup(&dma->video.entity);
>