| Message ID | 20191217075153.23766-1-peter.ujfalusi@ti.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | iio: adc: stm32-adc: Use dma_request_chan() instead dma_request_slave_channel() | expand |
On Tue, 17 Dec 2019 09:51:53 +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. > > Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> Hi Peter, Change looks sensible to me, but I'd like to leave a little longer for others to look at this. Give me a poke if I seem to have lost it by the end of the first week in Jan. Thanks, Jonathan > --- > drivers/iio/adc/stm32-adc.c | 10 ++++++++-- > 1 file changed, 8 insertions(+), 2 deletions(-) > > diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c > index 3b291d72701c..5dab23f1fdee 100644 > --- a/drivers/iio/adc/stm32-adc.c > +++ b/drivers/iio/adc/stm32-adc.c > @@ -1746,9 +1746,15 @@ static int stm32_adc_dma_request(struct iio_dev *indio_dev) > struct dma_slave_config config; > int ret; > > - adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx"); > - if (!adc->dma_chan) > + adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx"); > + if (IS_ERR(adc->dma_chan)) { > + if (PTR_ERR(adc->dma_chan) == -EPROBE_DEFER) > + return -EPROBE_DEFER; > + > + /* Ignore errors to fall back to IRQ mode */ > + adc->dma_chan = NULL; > return 0; > + } > > adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev, > STM32_DMA_BUFFER_SIZE,
On 12/23/19 4:42 PM, Jonathan Cameron wrote: > On Tue, 17 Dec 2019 09:51:53 +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. >> >> Signed-off-by: Peter Ujfalusi <peter.ujfalusi@ti.com> > Hi Peter, > > Change looks sensible to me, but I'd like to leave a little longer > for others to look at this. > > Give me a poke if I seem to have lost it by the end of the first > week in Jan. > > Thanks, > > Jonathan > >> --- >> drivers/iio/adc/stm32-adc.c | 10 ++++++++-- >> 1 file changed, 8 insertions(+), 2 deletions(-) >> >> diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c >> index 3b291d72701c..5dab23f1fdee 100644 >> --- a/drivers/iio/adc/stm32-adc.c >> +++ b/drivers/iio/adc/stm32-adc.c >> @@ -1746,9 +1746,15 @@ static int stm32_adc_dma_request(struct iio_dev *indio_dev) >> struct dma_slave_config config; >> int ret; >> >> - adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx"); >> - if (!adc->dma_chan) >> + adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx"); >> + if (IS_ERR(adc->dma_chan)) { >> + if (PTR_ERR(adc->dma_chan) == -EPROBE_DEFER) >> + return -EPROBE_DEFER; Hi Peter, Thanks for the patch and sorry for the late reply. I'd rather prefer to check explicitly for -ENODEV (as the DMA is optional) to use the IRQ mode and treat all other codes (including EPROBE_DEFER) as errors. Rationale is: This can hide other errors e.g. like all DMA channels are busy/reserved for other usage. So the user may wrongly think it's probing the driver, with DMA. This may be a corner case, but still... DMA channels are assigned via device tree. I'd rather prefer to avoid depending of runtime (probe ordering) in such a case. Can you update the patch considering this ? Please find here an alternate proposal: adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx"); if (IS_ERR(adc->dma_chan)) { if (PTR_ERR(adc->dma_chan) != -ENODEV) return PTR_ERR(adc->dma_chan); /* DMA is optional: fall back to IRQ mode */ adc->dma_chan = NULL; return 0; } Best regards, Fabrice >> + >> + /* Ignore errors to fall back to IRQ mode */ >> + adc->dma_chan = NULL; >> return 0; >> + } >> >> adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev, >> STM32_DMA_BUFFER_SIZE, >
diff --git a/drivers/iio/adc/stm32-adc.c b/drivers/iio/adc/stm32-adc.c index 3b291d72701c..5dab23f1fdee 100644 --- a/drivers/iio/adc/stm32-adc.c +++ b/drivers/iio/adc/stm32-adc.c @@ -1746,9 +1746,15 @@ static int stm32_adc_dma_request(struct iio_dev *indio_dev) struct dma_slave_config config; int ret; - adc->dma_chan = dma_request_slave_channel(&indio_dev->dev, "rx"); - if (!adc->dma_chan) + adc->dma_chan = dma_request_chan(&indio_dev->dev, "rx"); + if (IS_ERR(adc->dma_chan)) { + if (PTR_ERR(adc->dma_chan) == -EPROBE_DEFER) + return -EPROBE_DEFER; + + /* Ignore errors to fall back to IRQ mode */ + adc->dma_chan = NULL; return 0; + } adc->rx_buf = dma_alloc_coherent(adc->dma_chan->device->dev, STM32_DMA_BUFFER_SIZE,
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/iio/adc/stm32-adc.c | 10 ++++++++-- 1 file changed, 8 insertions(+), 2 deletions(-)