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

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