From mboxrd@z Thu Jan 1 00:00:00 1970 From: lee.jones@linaro.org (Lee Jones) Date: Tue, 23 Jan 2018 16:41:21 +0000 Subject: [PATCH 4/8] mfd: stm32-timers: add support for dmas In-Reply-To: References: <1516106631-18722-1-git-send-email-fabrice.gasnier@st.com> <1516106631-18722-5-git-send-email-fabrice.gasnier@st.com> <20180123133234.xmep76cgdremnj47@dell> <20180123153035.2rvhspe2m5ej57op@dell> Message-ID: <20180123164121.xjzhypqe2u5c7zza@dell> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On Tue, 23 Jan 2018, Fabrice Gasnier wrote: > On 01/23/2018 04:30 PM, Lee Jones wrote: > > On Tue, 23 Jan 2018, Fabrice Gasnier wrote: > > > >> On 01/23/2018 02:32 PM, Lee Jones wrote: > >>> On Tue, 16 Jan 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, keep reference of device's bus address to allow child drivers to > >>>> transfer data from/to device by using dma. > >>>> > >>>> Signed-off-by: Fabrice Gasnier > >>>> --- > >>>> drivers/mfd/stm32-timers.c | 37 ++++++++++++++++++++++++++++++++++++- > >>>> include/linux/mfd/stm32-timers.h | 14 ++++++++++++++ > >>>> 2 files changed, 50 insertions(+), 1 deletion(-) > >>>> > >>>> diff --git a/drivers/mfd/stm32-timers.c b/drivers/mfd/stm32-timers.c > >>>> static int stm32_timers_probe(struct platform_device *pdev) > >>>> { > >>>> struct device *dev = &pdev->dev; > >>>> @@ -44,6 +61,7 @@ static int stm32_timers_probe(struct platform_device *pdev) > >>>> mmio = devm_ioremap_resource(dev, res); > >>>> if (IS_ERR(mmio)) > >>>> return PTR_ERR(mmio); > >>>> + ddata->phys_base = res->start; > >>> > >>> What do you use this for? > >> > >> This is used in in child driver (pwm) for capture data transfer by dma. > > > > Might be worth being clear about that. > > > > Perhaps pass in 'dma_base' (phys_base + offset) instead? > > I guess you've had a look at [PATCH 5/8] pwm: stm32: add capture > support. Are you talking about passing phys_base + TIM_DMAR ? I have and I am. > If this is the case, I'd prefer to keep phys base only if you don't > mind, and handle TIM_DMAR offset in pwm driver. This way, all dma slave > config is kept locally at one place. > Or do you mean something else ? > > Maybe I can add a comment here about this ? > Something like: > /* phys_base to be used by child driver, e.g. DMA burst mode */ I haven't seen the memory map for this device, so it's not easy for me to comment, but passing in the physical address of the parent MFD into a child device doesn't quite sit right with me. At what level does TIM_DMAR sit? Is it a child (PWM) specific property, or is it described at parent (Timer) level? -- Lee Jones Linaro Services Technical Lead Linaro.org ? Open source software for ARM SoCs Follow Linaro: Facebook | Twitter | Blog