From mboxrd@z Thu Jan 1 00:00:00 1970 From: fabrice.gasnier@st.com (Fabrice Gasnier) Date: Tue, 17 Apr 2018 13:54:32 +0200 Subject: [PATCH v4 2/6] mfd: stm32-timers: add support for dmas In-Reply-To: <20180417101009.do42adq24ltgw4lt@dell> References: <1523895561-4073-1-git-send-email-fabrice.gasnier@st.com> <1523895561-4073-3-git-send-email-fabrice.gasnier@st.com> <20180417071250.yhgl7c7apn7w53xf@dell> <34e30463-6236-a8e4-fd1f-6217612375eb@st.com> <20180417101009.do42adq24ltgw4lt@dell> Message-ID: <72e211c8-7342-7722-e3e8-75442560bdfe@st.com> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 04/17/2018 12:10 PM, Lee Jones wrote: > On Tue, 17 Apr 2018, Fabrice Gasnier wrote: > >> On 04/17/2018 09:12 AM, Lee Jones wrote: >>> On Mon, 16 Apr 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 >>>> Reviewed-by: Benjamin Gaignard >>>> --- >>>> Changes in v4: >>>> - Lee's comments: Add kerneldoc header, better format comments. >>>> Changes in v3: >>>> - Basically Lee's comments: >>>> - rather create a struct stm32_timers_dma, and place a reference to it >>>> in existing ddata (instead of adding priv struct). >>>> - rather use a struct device in exported routine prototype, and use >>>> standard helpers instead of ddata. Get rid of to_stm32_timers_priv(). >>>> - simplify error handling in probe (remove a goto) >>>> - comment on devm_of_platform_*populate() usage. >>>> >>>> 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 | 227 ++++++++++++++++++++++++++++++++++++++- >>>> include/linux/mfd/stm32-timers.h | 32 ++++++ >>>> 2 files changed, 257 insertions(+), 2 deletions(-) >>> >>> [...] >>> >>>> diff --git a/include/linux/mfd/stm32-timers.h b/include/linux/mfd/stm32-timers.h >>>> index 2aadab6..a04d7a1 100644 >>>> --- a/include/linux/mfd/stm32-timers.h >>>> +++ b/include/linux/mfd/stm32-timers.h >>>> @@ -8,6 +8,8 @@ >>>> #define _LINUX_STM32_GPTIMER_H_ >>>> >>>> #include >>>> +#include >>>> +#include >>>> #include >>> >>> [...] >>> >>>> +struct stm32_timers_dma; >>>> + >>>> struct stm32_timers { >>>> struct clk *clk; >>>> struct regmap *regmap; >>>> u32 max_arr; >>>> + struct stm32_timers_dma *dma; /* Only to be used by the parent */ >>> >>> I'm confused. I thought the point of putting this comment in was so >>> that you could place the definition of 'stm32_timers_dma' and remove >>> the forward declaration? >> >> Hi Lee, >> >> Sorry, if I miss-understood the point then. So, do you wish I both: >> - move the full struct definition in above header ? >> - and keep this comment ? > > That was what I thought we agreed. Hi Lee, Ok, I'll update this in v5. BTW, I'll fix warning reported by Dan: > smatch warnings: drivers/mfd/stm32-timers.c:165 stm32_timers_dma_burst_read() warn: warn: dma_mapping_error() doesn't return an error code Thanks, Fabrice > However, I left the final decision to you. If you do not think this > is a reasonable i.e. the comment alone will not be enough to prevent > people from abusing the API, then leave it as it is. > > Bear in mind that I think this introduces a build dependency on the > MFD driver for *each and every* other source file which includes this > header. If you choose the current solution, you will need to handle > that accordingly. > >> +/** >> + * struct stm32_timers_dma - STM32 timer DMA handling. >> + * @completion: end of DMA transfer completion >> + * @phys_base: control registers physical base address >> + * @lock: protect DMA access >> + * @chan: DMA channel in use >> + * @chans: DMA channels available for this timer instance >> + */ >> +struct stm32_timers_dma { >> + struct completion completion; >> + phys_addr_t phys_base; >> + struct mutex lock; >> + struct dma_chan *chan; >> + struct dma_chan *chans[STM32_TIMERS_MAX_DMAS]; >> +}; >> >> This will basically expose the struct to child drivers. But I'm ok if >> you think this is acceptable. >> >> I can send a V5 if you wish... >> >> Please advise, >> Best regards, >> Fabrice >> >>> >>>> }; >>>> + >>>> +int stm32_timers_dma_burst_read(struct device *dev, u32 *buf, >>>> + enum stm32_timers_dmas id, u32 reg, >>>> + unsigned int num_reg, unsigned int bursts, >>>> + unsigned long tmo_ms); >>>> #endif >>> >