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SubjectRe: [PATCH v2] iio: adc: at91-sama5d2_adc: Use dma_request_chan() instead dma_request_slave_channel()
On Tue, 17 Dec 2019 12:31:00 +0200
Peter Ujfalusi <peter.ujfalusi@ti.com> 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.
Unfortunately that doesn't seem to be true.
The function in question returns void...

And for that matter is called only from the set_watermark callback which
doesn't run at probe time.

So if we were to get a deferred response at runtime there isn't a whole
lot we could do with it.

Jonathan



>
> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com>
> ---
> Hi,
>
> Changes since v1:
> - Subject prefix is corrected to "iio: adc: at91-sama5d2_adc:"
>
> Regards,
> Peter
>
> drivers/iio/adc/at91-sama5d2_adc.c | 6 +++---
> 1 file changed, 3 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/iio/adc/at91-sama5d2_adc.c b/drivers/iio/adc/at91-sama5d2_adc.c
> index e1850f3d5cf3..a5c7771227d5 100644
> --- a/drivers/iio/adc/at91-sama5d2_adc.c
> +++ b/drivers/iio/adc/at91-sama5d2_adc.c
> @@ -1444,10 +1444,10 @@ static void at91_adc_dma_init(struct platform_device *pdev)
> if (st->dma_st.dma_chan)
> return;
>
> - st->dma_st.dma_chan = dma_request_slave_channel(&pdev->dev, "rx");
> -
> - if (!st->dma_st.dma_chan) {
> + st->dma_st.dma_chan = dma_request_chan(&pdev->dev, "rx");
> + if (IS_ERR(st->dma_st.dma_chan)) {
> dev_info(&pdev->dev, "can't get DMA channel\n");
> + st->dma_st.dma_chan = NULL;
> goto dma_exit;
> }
>

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