On 03/29/2018 02:59 PM, Lee Jones wrote: > On Wed, 28 Mar 2018, Fabrice Gasnier wrote: > >> On 03/28/2018 05:22 PM, Lee Jones wrote: >>> On Wed, 14 Feb 2018, Fabrice Gasnier wrote: >>> >>>> STM32 Timers can support up to 7 DMA requests: >>>> - 4 channels, update, compare and trigger. >>>> Optionally request part, or all DMAs from stm32-timers MFD core. >>>> >>>> Also add routine to implement burst reads using DMA from timer registers. >>>> This is exported. So, it can be used by child drivers, PWM capture >>>> for instance (but not limited to). >>>> >>>> Signed-off-by: Fabrice Gasnier <fabrice.gasnier@xxxxxx> >>>> Reviewed-by: Benjamin Gaignard <benjamin.gaignard@xxxxxxxxxx> >>>> --- >>>> Changes in v2: >>>> - Abstract DMA handling from child driver: move it to MFD core >>>> - Add comments on optional dma support >>>> --- >>>> drivers/mfd/stm32-timers.c | 215 ++++++++++++++++++++++++++++++++++++++- >>>> include/linux/mfd/stm32-timers.h | 27 +++++ >>>> 2 files changed, 238 insertions(+), 4 deletions(-) >>>> >>>> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c >>>> index a6675a4..2cdad2c 100644 >>>> --- a/drivers/mfd/stm32-timers.c >>>> +++ b/drivers/mfd/stm32-timers.c > > [...] > >>>> + struct dma_chan *dmas[STM32_TIMERS_MAX_DMAS]; >>>> + struct stm32_timers ddata; >>> >>> This looks odd to me. Why can't you expand the current ddata >>> structure? Wouldn't it be better to create a stm32_timers_dma >>> structure to place all this information in (except *dev, that should >>> live in the ddata struct), then place a reference in the existing >>> stm32_timers struct? >> >> Maybe I miss-understand you here, from what we discussed in V1: >> https://lkml.org/lkml/2018/1/23/574 >>> ... "passing in the physical address of the parent MFD into >>> a child device doesn't quite sit right with me" >> I introduced this private struct in MFD parent, and completely hide it >> from the child. >> >> So, do you suggest to add struct definition here ? But make it part of >> struct stm32_timers *ddata? >> >> And only put declaration in include/linux/mfd/stm32-timers.h: >> + struct stm32_timers_dma; >> >> struct stm32_timers { >> struct clk *clk; >> struct regmap *regmap; >> u32 max_arr; >> + struct stm32_timers_dma; >> }; > > Yes, that's the basic idea. > >> I can probably spare the *dev then... use dev->parent in child driver. > > What would you use dev->parent for? Hi Lee, This is to follow your sugestion to use *dev instead of *ddata when calling stm32_timers_dma_burst_read(), the idea is to use it on child side: stm32_timers_dma_burst_read(dev->parent,...) from pwm driver. Then there is no need to keep *dev inside ddata struct. > > [...] > >>>> +static int stm32_timers_remove(struct platform_device *pdev) >>>> +{ >>>> + struct stm32_timers *ddata = platform_get_drvdata(pdev); >>>> + struct stm32_timers_priv *priv = to_stm32_timers_priv(ddata); >>>> + >>>> + of_platform_depopulate(&pdev->dev); >>> >>> Why can't you continue using devm_*? >> >> I can use devm_of_platform_depopulate() here if you prefer, and keep >> devm_of_platform_populate() in probe. > > The point of devm_* is that you don't have to call depopulate. > > It happens automatically once this driver is unbound. Ok, so to clarify, keeping devm_ here may be a bit racy: of_platform_depopulate will happen after dma has been released (there is no devm_ variant to release dma). Only way to prevent race condition here, is to enforce of_platform_depopulate() is called before dma release (e.g. in reverse order compared to probe). Do you wish I add a comment about it ? Best Regards, Fabrice > -- To unsubscribe from this list: send the line "unsubscribe devicetree" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
