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Date: Mon, 6 Jan 2020 15:57:33 +0100 From: Fabrice Gasnier <fabrice.gasnier@...com> To: Peter Ujfalusi <peter.ujfalusi@...com>, <lee.jones@...aro.org>, <mcoquelin.stm32@...il.com>, <alexandre.torgue@...com> CC: <vkoul@...nel.org>, <linux-stm32@...md-mailman.stormreply.com>, <linux-arm-kernel@...ts.infradead.org>, <linux-kernel@...r.kernel.org>, Benjamin GAIGNARD <benjamin.gaignard@...com> Subject: Re: [PATCH] mfd: stm32-timers: Use dma_request_chan() instead dma_request_slave_channel() On 12/20/19 12:36 PM, Peter Ujfalusi wrote: > Hi Fabrice, > > On 20/12/2019 10.54, Fabrice Gasnier wrote: >> 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@...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]); > > My intention was to specifically pick and handle EPROBE_DEFER while not > changing how the driver handles other errors, whether it because there > is no DMA channel specified or there is a failure to get the channel. > > But if you prefer to ignore only ENODEV and report other errors then I > can send v2. Hi Peter, Sorry for the late answer. Yes, I'd prefer this please, not to hide other error case (as detailed in other thread: https://lkml.org/lkml/2020/1/6/209). The only expected "normal" error here is -ENODEV, as the DMA is optional. > It could expose otherwise ignored configuration error (from DT?) and the > change in the driver will be blamed for the regression. I can do some testing at my end if needed, but I don't expect regression here. Thanks, Fabrice > > Would it make sense to add the change you suggested as an iteration on > top of this patch? > >> >>> + >>> + 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); >>> >>> > > Kind regards, > - Péter > > Texas Instruments Finland Oy, Porkkalankatu 22, 00180 Helsinki. > Y-tunnus/Business ID: 0615521-4. Kotipaikka/Domicile: Helsinki >
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