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SubjectRe: [PATCH] mfd: stm32-timers: Use dma_request_chan() instead dma_request_slave_channel()
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On 12/17/19 11:52 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@ti.com>
> ---
> drivers/mfd/stm32-timers.c | 31 ++++++++++++++++++++++---------
> 1 file changed, 22 insertions(+), 9 deletions(-)
>
> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c
> index efcd4b980c94..34747e8a4a40 100644
> --- a/drivers/mfd/stm32-timers.c
> +++ b/drivers/mfd/stm32-timers.c
> @@ -167,10 +167,11 @@ static void stm32_timers_get_arr_size(struct stm32_timers *ddata)
> regmap_write(ddata->regmap, TIM_ARR, 0x0);
> }
>
> -static void stm32_timers_dma_probe(struct device *dev,
> +static int stm32_timers_dma_probe(struct device *dev,
> struct stm32_timers *ddata)
> {
> int i;
> + int ret = 0;
> char name[4];
>
> init_completion(&ddata->dma.completion);
> @@ -179,14 +180,22 @@ static void stm32_timers_dma_probe(struct device *dev,
> /* Optional DMA support: get valid DMA channel(s) or NULL */
> for (i = STM32_TIMERS_DMA_CH1; i <= STM32_TIMERS_DMA_CH4; i++) {
> snprintf(name, ARRAY_SIZE(name), "ch%1d", i + 1);
> - ddata->dma.chans[i] = dma_request_slave_channel(dev, name);
> + ddata->dma.chans[i] = dma_request_chan(dev, name);
> }
> - ddata->dma.chans[STM32_TIMERS_DMA_UP] =
> - dma_request_slave_channel(dev, "up");
> - ddata->dma.chans[STM32_TIMERS_DMA_TRIG] =
> - dma_request_slave_channel(dev, "trig");
> - ddata->dma.chans[STM32_TIMERS_DMA_COM] =
> - dma_request_slave_channel(dev, "com");
> + ddata->dma.chans[STM32_TIMERS_DMA_UP] = dma_request_chan(dev, "up");
> + ddata->dma.chans[STM32_TIMERS_DMA_TRIG] = dma_request_chan(dev, "trig");
> + ddata->dma.chans[STM32_TIMERS_DMA_COM] = dma_request_chan(dev, "com");
> +
> + for (i = STM32_TIMERS_DMA_CH1; i < STM32_TIMERS_MAX_DMAS; i++) {
> + if (IS_ERR(ddata->dma.chans[i])) {
> + if (PTR_ERR(ddata->dma.chans[i]) == -EPROBE_DEFER)> + ret = -EPROBE_DEFER;

Hi Peter,

Thanks for the patch,

As the DMA is optional, I'd rather prefer to check explicitly there's no
device, and return any other error case, basically:

if (PTR_ERR(ddata->dma.chans[i]) != -ENODEV)
return PTR_ERR(ddata->dma.chans[i]);

> +
> + ddata->dma.chans[i] = NULL;
> + }
> + }
> +
> + return ret;

With that, return 0 here.

> }
>
> static void stm32_timers_dma_remove(struct device *dev,
> @@ -230,7 +239,11 @@ static int stm32_timers_probe(struct platform_device *pdev)
>
> stm32_timers_get_arr_size(ddata);
>
> - stm32_timers_dma_probe(dev, ddata);
> + ret = stm32_timers_dma_probe(dev, ddata);
> + if (ret) {
> + stm32_timers_dma_remove(dev, ddata);

With that, stm32_timers_dma_remove() likely need to be updated:

- if (ddata->dma.chans[i])
+ if (!IS_ERR_OR_NULL(ddata->dma.chans[i]))
dma_release_channel(ddata->dma.chans[i]);

Best regards,
Fabrice

> + return ret;
> + }
>
> platform_set_drvdata(pdev, ddata);
>
>

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