On 16/04/2020 11.46, Lee Jones wrote: > On Tue, 07 Jan 2020, 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 <[email protected]> >> --- >> Hi, >> >> Changes since v1: >> - Fall back to PIO mode only in case of ENODEV and report all other errors >> >> Regards, >> Peter >> >> drivers/mfd/stm32-timers.c | 32 +++++++++++++++++++++++--------- >> 1 file changed, 23 insertions(+), 9 deletions(-) > > Apologies for not spotting this patch sooner, it had slipped through > the net. If this happens again, please just submit a [RESEND].
No issues, I have also forgot about it ;)
>> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c
>> index efcd4b980c94..add603359124 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 +180,23 @@ 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])) {
>> + /* Save the first error code to return */
>> + if (PTR_ERR(ddata->dma.chans[i]) != -ENODEV && !ret)
>> + ret = PTR_ERR(ddata->dma.chans[i]);
>> +
>> + ddata->dma.chans[i] = NULL;
>> + }
>> + }
>
> In my mind, it doesn't make sense to keep requesting channels if an
> error has occurred. Please remove all of the added complexity caused
> by the for() loop and simply check the return value after each call to
> dma_request_chan(), returning immediately on error.
Yes. I have intentionally done the patch this way to _not_ change the
behavior in any ways as it is not up to me to decide what is good or bad
for a driver I can not test.
>
>> + return ret;
>> }
>
- Péter
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