linux-kernel - Re: [PATCH] media: stm32-dcmi: Use dma_request_chan() instead dma_request_slave

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Message-ID: <a4682783-e966-6176-4ab5-cc9345e3508f@ti.com>
Date:   Tue, 7 Jan 2020 12:38:56 +0200
From:   Peter Ujfalusi <peter.ujfalusi@...com>
To:     Hugues FRUCHET <hugues.fruchet@...com>,
        "mchehab@...nel.org" <mchehab@...nel.org>,
        "mcoquelin.stm32@...il.com" <mcoquelin.stm32@...il.com>,
        Alexandre TORGUE <alexandre.torgue@...com>
CC:     "vkoul@...nel.org" <vkoul@...nel.org>,
        "linux-media@...r.kernel.org" <linux-media@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-stm32@...md-mailman.stormreply.com" 
        <linux-stm32@...md-mailman.stormreply.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH] media: stm32-dcmi: Use dma_request_chan() instead
 dma_request_slave_channel()

Hi Hugues,

On 07/01/2020 11.46, Hugues FRUCHET wrote:
> Hi Peter,
> 
> If not too late, could you change trace to only trig error trace when
> error is not "probe defered" ? See below:
> 
> -	chan = dma_request_slave_channel(&pdev->dev, "tx");
> -	if (!chan) {
> -		dev_info(&pdev->dev, "Unable to request DMA channel, defer probing\n");
> -		return -EPROBE_DEFER;
> +	chan = dma_request_chan(&pdev->dev, "tx");
> +	if (IS_ERR(chan)) {
> +		if (PTR_ERR(chan) != -EPROBE_DEFER)
> +			dev_err(&pdev->dev, "Unable to request DMA channel\n");
> +		return PTR_ERR(chan);

Sure, I don't know how I missed it.

Regards,
- Péter

> 
> Best regards,
> Hugues.
> 
> On 12/18/19 11:52 AM, Hugues FRUCHET wrote:
>> Thanks for patching Peter,
>>
>> No regression observed on my side.
>>
>> Acked-by: Hugues Fruchet <hugues.fruchet@...com>
>>
>> Best regards,
>> Hugues.
>>
>> On 12/17/19 11:41 AM, 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>
>>> ---
>>>   drivers/media/platform/stm32/stm32-dcmi.c | 6 +++---
>>>   1 file changed, 3 insertions(+), 3 deletions(-)
>>>
>>> diff --git a/drivers/media/platform/stm32/stm32-dcmi.c 
>>> b/drivers/media/platform/stm32/stm32-dcmi.c
>>> index 9392e3409fba..55351872b0c7 100644
>>> --- a/drivers/media/platform/stm32/stm32-dcmi.c
>>> +++ b/drivers/media/platform/stm32/stm32-dcmi.c
>>> @@ -1910,10 +1910,10 @@ static int dcmi_probe(struct platform_device 
>>> *pdev)
>>>           return PTR_ERR(mclk);
>>>       }
>>> -    chan = dma_request_slave_channel(&pdev->dev, "tx");
>>> -    if (!chan) {
>>> +    chan = dma_request_chan(&pdev->dev, "tx");
>>> +    if (IS_ERR(chan)) {
>>>           dev_info(&pdev->dev, "Unable to request DMA channel, defer 
>>> probing\n");
>>> -        return -EPROBE_DEFER;
>>> +        return PTR_ERR(chan);
>>>       }
>>>       spin_lock_init(&dcmi->irqlock);
>> >


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