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From: Lee Jones <lee.jones-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org>
To: Fabrice Gasnier <fabrice.gasnier-qxv4g6HH51o@public.gmane.org>
Cc: thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	robh+dt-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org,
	alexandre.torgue-qxv4g6HH51o@public.gmane.org,
	benjamin.gaignard-QSEj5FYQhm4dnm+yROfE0A@public.gmane.org,
	mark.rutland-5wv7dgnIgG8@public.gmane.org,
	linux-I+IVW8TIWO2tmTQ+vhA3Yw@public.gmane.org,
	mcoquelin.stm32-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org,
	benjamin.gaignard-qxv4g6HH51o@public.gmane.org,
	devicetree-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-pwm-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 4/8] mfd: stm32-timers: add support for dmas
Date: Tue, 23 Jan 2018 16:41:21 +0000	[thread overview]
Message-ID: <20180123164121.xjzhypqe2u5c7zza@dell> (raw)
In-Reply-To: <ee021839-3298-d01b-8890-619aca0399a7-qxv4g6HH51o@public.gmane.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 <fabrice.gasnier-qxv4g6HH51o@public.gmane.org>
> >>>> ---
> >>>>  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
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  parent reply	other threads:[~2018-01-23 16:41 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-01-16 12:43 [PATCH 0/8] Add support for PWM input capture on STM32 Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 1/8] pwm: stm32: fix, remove unused struct device Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 2/8] pwm: stm32: protect common prescaler for all channels Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 3/8] dt-bindings: mfd: stm32-timers: add support for dmas Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 4/8] " Fabrice Gasnier
     [not found]   ` <1516106631-18722-5-git-send-email-fabrice.gasnier-qxv4g6HH51o@public.gmane.org>
2018-01-23 13:32     ` Lee Jones
2018-01-23 13:57       ` Fabrice Gasnier
     [not found]         ` <e611b40f-bd37-aa2d-afd9-997b86d55441-qxv4g6HH51o@public.gmane.org>
2018-01-23 15:30           ` Lee Jones
2018-01-23 15:52             ` Fabrice Gasnier
     [not found]               ` <ee021839-3298-d01b-8890-619aca0399a7-qxv4g6HH51o@public.gmane.org>
2018-01-23 16:41                 ` Lee Jones [this message]
2018-01-24  8:40                   ` Fabrice Gasnier
2018-01-24 14:56                     ` Lee Jones
2018-01-24 15:30                       ` Fabrice Gasnier
2018-01-24 15:43                         ` cas
2018-01-16 12:43 ` [PATCH 5/8] pwm: stm32: add capture support Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 6/8] pwm: stm32: improve capture by tuning counter prescaler Fabrice Gasnier
     [not found] ` <1516106631-18722-1-git-send-email-fabrice.gasnier-qxv4g6HH51o@public.gmane.org>
2018-01-16 12:43   ` [PATCH 7/8] pwm: stm32: use input prescaler to improve period capture Fabrice Gasnier
2018-01-16 12:43 ` [PATCH 8/8] ARM: dts: stm32: Enable pwm3 input capture on stm32f429i-eval Fabrice Gasnier

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