[PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Peter Ujfalusi]

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@ti.com>
---
Hi,

Changes since v1:
- Fall back to IRQ mode for ADC only in case of ENODEV

Regards,
Peter

 drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
 1 file changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
index e493242c266e..74a2211bdff4 100644
--- a/drivers/iio/adc/stm32-dfsdm-adc.c
+++ b/drivers/iio/adc/stm32-dfsdm-adc.c
@@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
 {
 	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
 
-	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
-	if (!adc->dma_chan)
-		return -EINVAL;
+	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
+	if (IS_ERR(adc->dma_chan)) {
+		int ret = PTR_ERR(adc->dma_chan);
+
+		adc->dma_chan = NULL;
+		return ret;
+	}
 
 	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
 					 DFSDM_DMA_BUFFER_SIZE,
@@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
 	init_completion(&adc->completion);
 
 	/* Optionally request DMA */
-	if (stm32_dfsdm_dma_request(indio_dev)) {
+	ret = stm32_dfsdm_dma_request(indio_dev);
+	if (ret) {
+		if (ret != -ENODEV) {
+			if (ret != -EPROBE_DEFER)
+				dev_err(&indio_dev->dev,
+					"DMA channel request failed with %d\n",
+					ret);
+			return ret;
+		}
+
 		dev_dbg(&indio_dev->dev, "No DMA support\n");
 		return 0;
 	}
-- 
Peter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Re: [Linux-stm32] [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Olivier MOYSAN]

Acked-by: Olivier Moysan <olivier.moysan@st.com>

On 1/7/20 12:45 PM, 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@ti.com>
> ---
> Hi,
>
> Changes since v1:
> - Fall back to IRQ mode for ADC only in case of ENODEV
>
> Regards,
> Peter
>
>   drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>   1 file changed, 17 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> index e493242c266e..74a2211bdff4 100644
> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>   {
>   	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>   
> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
> -	if (!adc->dma_chan)
> -		return -EINVAL;
> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
> +	if (IS_ERR(adc->dma_chan)) {
> +		int ret = PTR_ERR(adc->dma_chan);
> +
> +		adc->dma_chan = NULL;
> +		return ret;
> +	}
>   
>   	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>   					 DFSDM_DMA_BUFFER_SIZE,
> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>   	init_completion(&adc->completion);
>   
>   	/* Optionally request DMA */
> -	if (stm32_dfsdm_dma_request(indio_dev)) {
> +	ret = stm32_dfsdm_dma_request(indio_dev);
> +	if (ret) {
> +		if (ret != -ENODEV) {
> +			if (ret != -EPROBE_DEFER)
> +				dev_err(&indio_dev->dev,
> +					"DMA channel request failed with %d\n",
> +					ret);
> +			return ret;
> +		}
> +
>   		dev_dbg(&indio_dev->dev, "No DMA support\n");
>   		return 0;
>   	}

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Fabrice Gasnier]

On 1/7/20 12:45 PM, 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@ti.com>
> ---
> Hi,
> 
> Changes since v1:
> - Fall back to IRQ mode for ADC only in case of ENODEV

Hi Peter,

Thanks for the patch,

Please find a minor comment here after. Apart from that, you can add my:

Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>


> 
> Regards,
> Peter
> 
>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>  1 file changed, 17 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> index e493242c266e..74a2211bdff4 100644
> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>  {
>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>  
> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
> -	if (!adc->dma_chan)
> -		return -EINVAL;
> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
> +	if (IS_ERR(adc->dma_chan)) {
> +		int ret = PTR_ERR(adc->dma_chan);
> +
> +		adc->dma_chan = NULL;
> +		return ret;

You may "return PTR_ERR(adc->dma_chan);" directly here.

Best Regards,
Fabrice

> +	}
>  
>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>  					 DFSDM_DMA_BUFFER_SIZE,
> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>  	init_completion(&adc->completion);
>  
>  	/* Optionally request DMA */
> -	if (stm32_dfsdm_dma_request(indio_dev)) {
> +	ret = stm32_dfsdm_dma_request(indio_dev);
> +	if (ret) {
> +		if (ret != -ENODEV) {
> +			if (ret != -EPROBE_DEFER)
> +				dev_err(&indio_dev->dev,
> +					"DMA channel request failed with %d\n",
> +					ret);
> +			return ret;
> +		}
> +
>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
>  		return 0;
>  	}
> 

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Peter Ujfalusi]

On 09/01/2020 11.13, Fabrice Gasnier wrote:
> On 1/7/20 12:45 PM, 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@ti.com>
>> ---
>> Hi,
>>
>> Changes since v1:
>> - Fall back to IRQ mode for ADC only in case of ENODEV
> 
> Hi Peter,
> 
> Thanks for the patch,
> 
> Please find a minor comment here after. Apart from that, you can add my:
> 
> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> 
> 
>>
>> Regards,
>> Peter
>>
>>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>>  1 file changed, 17 insertions(+), 4 deletions(-)
>>
>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
>> index e493242c266e..74a2211bdff4 100644
>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>>  {
>>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>>  
>> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
>> -	if (!adc->dma_chan)
>> -		return -EINVAL;
>> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
>> +	if (IS_ERR(adc->dma_chan)) {
>> +		int ret = PTR_ERR(adc->dma_chan);
>> +
>> +		adc->dma_chan = NULL;
>> +		return ret;
> 
> You may "return PTR_ERR(adc->dma_chan);" directly here.

I don't make decision here on behalf of the adc path on to go forward w/
or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
needs the dma_chan to be NULL in case we don't use DMA.

It is much cleaner to set dma_chan to NULL here than doing it in other
paths.

> 
> Best Regards,
> Fabrice
> 
>> +	}
>>  
>>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>>  					 DFSDM_DMA_BUFFER_SIZE,
>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>>  	init_completion(&adc->completion);
>>  
>>  	/* Optionally request DMA */
>> -	if (stm32_dfsdm_dma_request(indio_dev)) {
>> +	ret = stm32_dfsdm_dma_request(indio_dev);
>> +	if (ret) {
>> +		if (ret != -ENODEV) {
>> +			if (ret != -EPROBE_DEFER)
>> +				dev_err(&indio_dev->dev,
>> +					"DMA channel request failed with %d\n",
>> +					ret);
>> +			return ret;
>> +		}
>> +
>>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
>>  		return 0;
>>  	}
>>

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Fabrice Gasnier]

On 1/9/20 11:32 AM, Peter Ujfalusi wrote:
> 
> 
> On 09/01/2020 11.13, Fabrice Gasnier wrote:
>> On 1/7/20 12:45 PM, 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@ti.com>
>>> ---
>>> Hi,
>>>
>>> Changes since v1:
>>> - Fall back to IRQ mode for ADC only in case of ENODEV
>>
>> Hi Peter,
>>
>> Thanks for the patch,
>>
>> Please find a minor comment here after. Apart from that, you can add my:
>>
>> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
>>
>>
>>>
>>> Regards,
>>> Peter
>>>
>>>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>>>  1 file changed, 17 insertions(+), 4 deletions(-)
>>>
>>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
>>> index e493242c266e..74a2211bdff4 100644
>>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
>>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
>>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>>>  {
>>>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>>>  
>>> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
>>> -	if (!adc->dma_chan)
>>> -		return -EINVAL;
>>> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
>>> +	if (IS_ERR(adc->dma_chan)) {
>>> +		int ret = PTR_ERR(adc->dma_chan);
>>> +
>>> +		adc->dma_chan = NULL;
>>> +		return ret;
>>
>> You may "return PTR_ERR(adc->dma_chan);" directly here.
> 
> I don't make decision here on behalf of the adc path on to go forward w/
> or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
> needs the dma_chan to be NULL in case we don't use DMA.
> 
> It is much cleaner to set dma_chan to NULL here than doing it in other
> paths.

Hi Peter,

Sorry I wasn't clear enough. I agree with you. I was suggesting only,
talking about the 'ret' variable. It may be removed to spare a few lines
:-).
	if (IS_ERR(adc->dma_chan)) {
		adc->dma_chan = NULL;
		return PTR_ERR(adc->dma_chan);
	}
I'm okay both ways.

> 
>>
>> Best Regards,
>> Fabrice
>>
>>> +	}
>>>  
>>>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>>>  					 DFSDM_DMA_BUFFER_SIZE,
>>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>>>  	init_completion(&adc->completion);
>>>  
>>>  	/* Optionally request DMA */
>>> -	if (stm32_dfsdm_dma_request(indio_dev)) {
>>> +	ret = stm32_dfsdm_dma_request(indio_dev);
>>> +	if (ret) {
>>> +		if (ret != -ENODEV) {
>>> +			if (ret != -EPROBE_DEFER)
>>> +				dev_err(&indio_dev->dev,
>>> +					"DMA channel request failed with %d\n",
>>> +					ret);
>>> +			return ret;
>>> +		}
>>> +
>>>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
>>>  		return 0;
>>>  	}
>>>
> 
> - Péter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Peter Ujfalusi]

On 09/01/2020 13.29, Fabrice Gasnier wrote:
> On 1/9/20 11:32 AM, Peter Ujfalusi wrote:
>>
>>
>> On 09/01/2020 11.13, Fabrice Gasnier wrote:
>>> On 1/7/20 12:45 PM, 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@ti.com>
>>>> ---
>>>> Hi,
>>>>
>>>> Changes since v1:
>>>> - Fall back to IRQ mode for ADC only in case of ENODEV
>>>
>>> Hi Peter,
>>>
>>> Thanks for the patch,
>>>
>>> Please find a minor comment here after. Apart from that, you can add my:
>>>
>>> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
>>>
>>>
>>>>
>>>> Regards,
>>>> Peter
>>>>
>>>>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>>>>  1 file changed, 17 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>> index e493242c266e..74a2211bdff4 100644
>>>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
>>>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>>>>  {
>>>>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>>>>  
>>>> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
>>>> -	if (!adc->dma_chan)
>>>> -		return -EINVAL;
>>>> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
>>>> +	if (IS_ERR(adc->dma_chan)) {
>>>> +		int ret = PTR_ERR(adc->dma_chan);
>>>> +
>>>> +		adc->dma_chan = NULL;
>>>> +		return ret;
>>>
>>> You may "return PTR_ERR(adc->dma_chan);" directly here.
>>
>> I don't make decision here on behalf of the adc path on to go forward w/
>> or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
>> needs the dma_chan to be NULL in case we don't use DMA.
>>
>> It is much cleaner to set dma_chan to NULL here than doing it in other
>> paths.
> 
> Hi Peter,

Hi Fabrice,

> Sorry I wasn't clear enough. I agree with you. I was suggesting only,
> talking about the 'ret' variable. It may be removed to spare a few lines
> :-).
> 	if (IS_ERR(adc->dma_chan)) {
> 		adc->dma_chan = NULL;
> 		return PTR_ERR(adc->dma_chan);
> 	}
> I'm okay both ways.

PTR_ERR(NULL); will return 0
I need to retrieve the actual error code before NULLing dma_chan.

> 
>>
>>>
>>> Best Regards,
>>> Fabrice
>>>
>>>> +	}
>>>>  
>>>>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>>>>  					 DFSDM_DMA_BUFFER_SIZE,
>>>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>>>>  	init_completion(&adc->completion);
>>>>  
>>>>  	/* Optionally request DMA */
>>>> -	if (stm32_dfsdm_dma_request(indio_dev)) {
>>>> +	ret = stm32_dfsdm_dma_request(indio_dev);
>>>> +	if (ret) {
>>>> +		if (ret != -ENODEV) {
>>>> +			if (ret != -EPROBE_DEFER)
>>>> +				dev_err(&indio_dev->dev,
>>>> +					"DMA channel request failed with %d\n",
>>>> +					ret);
>>>> +			return ret;
>>>> +		}
>>>> +
>>>>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
>>>>  		return 0;
>>>>  	}
>>>>
>>
>> - Péter
>>
>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>

- Péter

Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Fabrice Gasnier]

On 1/9/20 12:40 PM, Peter Ujfalusi wrote:
> 
> 
> On 09/01/2020 13.29, Fabrice Gasnier wrote:
>> On 1/9/20 11:32 AM, Peter Ujfalusi wrote:
>>>
>>>
>>> On 09/01/2020 11.13, Fabrice Gasnier wrote:
>>>> On 1/7/20 12:45 PM, 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@ti.com>
>>>>> ---
>>>>> Hi,
>>>>>
>>>>> Changes since v1:
>>>>> - Fall back to IRQ mode for ADC only in case of ENODEV
>>>>
>>>> Hi Peter,
>>>>
>>>> Thanks for the patch,
>>>>
>>>> Please find a minor comment here after. Apart from that, you can add my:
>>>>
>>>> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
>>>>
>>>>
>>>>>
>>>>> Regards,
>>>>> Peter
>>>>>
>>>>>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
>>>>>  1 file changed, 17 insertions(+), 4 deletions(-)
>>>>>
>>>>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> index e493242c266e..74a2211bdff4 100644
>>>>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
>>>>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
>>>>>  {
>>>>>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
>>>>>  
>>>>> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
>>>>> -	if (!adc->dma_chan)
>>>>> -		return -EINVAL;
>>>>> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
>>>>> +	if (IS_ERR(adc->dma_chan)) {
>>>>> +		int ret = PTR_ERR(adc->dma_chan);
>>>>> +
>>>>> +		adc->dma_chan = NULL;
>>>>> +		return ret;
>>>>
>>>> You may "return PTR_ERR(adc->dma_chan);" directly here.
>>>
>>> I don't make decision here on behalf of the adc path on to go forward w/
>>> or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
>>> needs the dma_chan to be NULL in case we don't use DMA.
>>>
>>> It is much cleaner to set dma_chan to NULL here than doing it in other
>>> paths.
>>
>> Hi Peter,
> 
> Hi Fabrice,
> 
>> Sorry I wasn't clear enough. I agree with you. I was suggesting only,
>> talking about the 'ret' variable. It may be removed to spare a few lines
>> :-).
>> 	if (IS_ERR(adc->dma_chan)) {
>> 		adc->dma_chan = NULL;
>> 		return PTR_ERR(adc->dma_chan);
>> 	}
>> I'm okay both ways.
> 
> PTR_ERR(NULL); will return 0
> I need to retrieve the actual error code before NULLing dma_chan.

Oh yes, so please forget this.
Thanks,
Fabrice

> 
>>
>>>
>>>>
>>>> Best Regards,
>>>> Fabrice
>>>>
>>>>> +	}
>>>>>  
>>>>>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
>>>>>  					 DFSDM_DMA_BUFFER_SIZE,
>>>>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
>>>>>  	init_completion(&adc->completion);
>>>>>  
>>>>>  	/* Optionally request DMA */
>>>>> -	if (stm32_dfsdm_dma_request(indio_dev)) {
>>>>> +	ret = stm32_dfsdm_dma_request(indio_dev);
>>>>> +	if (ret) {
>>>>> +		if (ret != -ENODEV) {
>>>>> +			if (ret != -EPROBE_DEFER)
>>>>> +				dev_err(&indio_dev->dev,
>>>>> +					"DMA channel request failed with %d\n",
>>>>> +					ret);
>>>>> +			return ret;
>>>>> +		}
>>>>> +
>>>>>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
>>>>>  		return 0;
>>>>>  	}
>>>>>
>>>
>>> - Péter
>>>
>>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
>>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
>>>
> 
> - Péter
> 
> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> 

Re: [PATCH v2] iio: adc: stm32-dfsdm: Use dma_request_chan() instead dma_request_slave_channel()

[Jonathan Cameron]

On Thu, 9 Jan 2020 13:56:14 +0100
Fabrice Gasnier <fabrice.gasnier@st.com> wrote:

> On 1/9/20 12:40 PM, Peter Ujfalusi wrote:
> > 
> > 
> > On 09/01/2020 13.29, Fabrice Gasnier wrote:  
> >> On 1/9/20 11:32 AM, Peter Ujfalusi wrote:  
> >>>
> >>>
> >>> On 09/01/2020 11.13, Fabrice Gasnier wrote:  
> >>>> On 1/7/20 12:45 PM, 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@ti.com>
> >>>>> ---
> >>>>> Hi,
> >>>>>
> >>>>> Changes since v1:
> >>>>> - Fall back to IRQ mode for ADC only in case of ENODEV  
> >>>>
> >>>> Hi Peter,
> >>>>
> >>>> Thanks for the patch,
> >>>>
> >>>> Please find a minor comment here after. Apart from that, you can add my:
> >>>>
> >>>> Acked-by: Fabrice Gasnier <fabrice.gasnier@st.com>
> >>>>
> >>>>  
> >>>>>
> >>>>> Regards,
> >>>>> Peter
> >>>>>
> >>>>>  drivers/iio/adc/stm32-dfsdm-adc.c | 21 +++++++++++++++++----
> >>>>>  1 file changed, 17 insertions(+), 4 deletions(-)
> >>>>>
> >>>>> diff --git a/drivers/iio/adc/stm32-dfsdm-adc.c b/drivers/iio/adc/stm32-dfsdm-adc.c
> >>>>> index e493242c266e..74a2211bdff4 100644
> >>>>> --- a/drivers/iio/adc/stm32-dfsdm-adc.c
> >>>>> +++ b/drivers/iio/adc/stm32-dfsdm-adc.c
> >>>>> @@ -1383,9 +1383,13 @@ static int stm32_dfsdm_dma_request(struct iio_dev *indio_dev)
> >>>>>  {
> >>>>>  	struct stm32_dfsdm_adc *adc = iio_priv(indio_dev);
> >>>>>  
> >>>>> -	adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx");
> >>>>> -	if (!adc->dma_chan)
> >>>>> -		return -EINVAL;
> >>>>> +	adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx");
> >>>>> +	if (IS_ERR(adc->dma_chan)) {
> >>>>> +		int ret = PTR_ERR(adc->dma_chan);
> >>>>> +
> >>>>> +		adc->dma_chan = NULL;
> >>>>> +		return ret;  
> >>>>
> >>>> You may "return PTR_ERR(adc->dma_chan);" directly here.  
> >>>
> >>> I don't make decision here on behalf of the adc path on to go forward w/
> >>> or w/o DMA support and if we go ahead the stm32_dfsdm_dma_release()
> >>> needs the dma_chan to be NULL in case we don't use DMA.
> >>>
> >>> It is much cleaner to set dma_chan to NULL here than doing it in other
> >>> paths.  
> >>
> >> Hi Peter,  
> > 
> > Hi Fabrice,
> >   
> >> Sorry I wasn't clear enough. I agree with you. I was suggesting only,
> >> talking about the 'ret' variable. It may be removed to spare a few lines
> >> :-).
> >> 	if (IS_ERR(adc->dma_chan)) {
> >> 		adc->dma_chan = NULL;
> >> 		return PTR_ERR(adc->dma_chan);
> >> 	}
> >> I'm okay both ways.  
> > 
> > PTR_ERR(NULL); will return 0
> > I need to retrieve the actual error code before NULLing dma_chan.  
> 
> Oh yes, so please forget this.
> Thanks,
> Fabrice

Applied to the togreg branch of iio.git and pushed out as testing.
Note I'll need to rebase once Greg pushes out staging/staging-next
with the changes currently in staging/staging-testing.  Shouldn't
have an effect on this though!

Thanks,

Jonathan

> 
> >   
> >>  
> >>>  
> >>>>
> >>>> Best Regards,
> >>>> Fabrice
> >>>>  
> >>>>> +	}
> >>>>>  
> >>>>>  	adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev,
> >>>>>  					 DFSDM_DMA_BUFFER_SIZE,
> >>>>> @@ -1509,7 +1513,16 @@ static int stm32_dfsdm_adc_init(struct iio_dev *indio_dev)
> >>>>>  	init_completion(&adc->completion);
> >>>>>  
> >>>>>  	/* Optionally request DMA */
> >>>>> -	if (stm32_dfsdm_dma_request(indio_dev)) {
> >>>>> +	ret = stm32_dfsdm_dma_request(indio_dev);
> >>>>> +	if (ret) {
> >>>>> +		if (ret != -ENODEV) {
> >>>>> +			if (ret != -EPROBE_DEFER)
> >>>>> +				dev_err(&indio_dev->dev,
> >>>>> +					"DMA channel request failed with %d\n",
> >>>>> +					ret);
> >>>>> +			return ret;
> >>>>> +		}
> >>>>> +
> >>>>>  		dev_dbg(&indio_dev->dev, "No DMA support\n");
> >>>>>  		return 0;
> >>>>>  	}
> >>>>>  
> >>>
> >>> - Péter
> >>>
> >>> Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> >>> Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> >>>  
> > 
> > - Péter
> > 
> > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki.
> > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki
> >