linux-kernel - Re: [PATCH v2 3/3] mfd: add CSR SiRFSoC on-chip power management module driver

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Date:	Mon, 5 Oct 2015 11:22:11 +0100
From:	Lee Jones <lee.jones@...aro.org>
To:	Barry Song <21cnbao@...il.com>
Cc:	Mark Brown <broonie@...nel.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	sameo <sameo@...ux.intel.com>,
	LKML <linux-kernel@...r.kernel.org>,
	DL-SHA-WorkGroupLinux <workgroup.linux@....com>,
	Guo Zeng <Guo.Zeng@....com>, Barry Song <Baohua.Song@....com>
Subject: Re: [PATCH v2 3/3] mfd: add CSR SiRFSoC on-chip power management
 module driver

On Mon, 05 Oct 2015, Barry Song wrote:

> 2015-10-05 16:21 GMT+08:00 Lee Jones <lee.jones@...aro.org>:
> > On Sun, 04 Oct 2015, Barry Song wrote:
> >> 2015-09-29 16:55 GMT+08:00 Lee Jones <lee.jones@...aro.org>:
> >> > On Tue, 29 Sep 2015, Barry Song wrote:
> >> >
> >> >> 2015-09-29 15:16 GMT+08:00 Lee Jones <lee.jones@...aro.org>:
> >> >> > On Tue, 29 Sep 2015, Barry Song wrote:
> >> >> >> >> >> +static int sirfsoc_pwrc_probe(struct platform_device *pdev)
> >> >> >> >> >> +{
> >> >> >> >> >> +     struct device_node *np = pdev->dev.of_node;
> >> >> >> >> >> +     const struct of_device_id *match;
> >> >> >> >> >> +     struct sirfsoc_pwrc_info *pwrcinfo;
> >> >> >> >> >> +     struct regmap_irq_chip *regmap_irq_chip;
> >> >> >> >> >> +     struct sirfsoc_pwrc_register *pwrc_reg;
> >> >> >> >> >> +     struct regmap *map;
> >> >> >> >> >> +     int ret;
> >> >> >> >> >> +     u32 base;
> >> >> >> >> >> +
> >> >> >> >> >> +     if (of_property_read_u32(np, "reg", &base))
> >> >> >> >> >> +             panic("unable to find base address of pwrc node in dtb\n");
> >> >> >> >> >
> >> >> >> >> > It looks like this driver should depend on OF.
> >> >> >> >> >
> >> >> >> >> > Why are you obtaining the base address manually? Use:
> >> >> >> >> >
> >> >> >> >> >   res = platform_get_resource();
> >> >> >> >> >   devm_ioremap_resource(res);
> >> >> >> >> >
> >> >> >> >> > ... instead.
> >> >> >> >>
> >> >> >> >> this was explained as they are not in memory space, they are behind a
> >> >> >> >> bus bridge.
> >> >> >> >
> >> >> >> > Use 'ranges' in the DT, then you can pull out the proper address
> >> >> >> > without hand rolling your own method.
> >> >> >>
> >> >> >> it seems it is not a "ranges" thing,  things behind rtciobrg is much
> >> >> >> like things behind USB or sdio. we need to use a rtciobrg protocol to
> >> >> >> do read/write.
> >> >> >> they can not be randomly accessed by load/store, and can't be XIP.
> >> >> >> they don't have any ranges in CPU memory space.
> >> >> >
> >> >> > So what's the point of 'base' then?  I assumed this was the base of
> >> >> > the IP registers which where memory mapped?
> >> >>
> >> >> just think we have a i2c device, and this i2c device has multi-functions.
> >> >> each function has a base of its register offset.
> >> >> actually, the base is the offset of 1st register.
> >> >
> >> > Does it every change, from device to device?
> >
> > What I mean is ...
> 
> i get you now :-)
> 
> >
> >> yes. Lee. e.g:
> >>
> >>                         rtc-iobg@...40000 {
> >>                                 reg = <0x18840000 0x1000>;
> >>
> >>                                 sysrtc@...0 {
> >
> > Is sysrtc always @2000, or might it be @4000 on some devices?
> 
> 
> that depends on the IC design. technically, they can be anywhere and
> in any order behind rtc-iobridge.
> good luck is the existing SoCs such as prima2, atlas6, atlas7 all put
> it at 2000.
> 
> >
> >>                                         compatible = "sirf,prima2-sysrtc";
> >>                                         reg = <0x2000 0x100>;
> >>                                         interrupts = <0 52 0>;
> >>                                 };
> >>                                 pwrc@...0 {
> >
> > Same for pwrc?
> 
> all of the existing prima2, atlas6, atlas7 chips put it at 3000. so
> the problem is it a hardware OF property or a const/MARCO?
> i feel it is a OF property. it is pretty much similar with we can put
> a i2c, spi ,usb controller in different memory place in memory bus.

Right, this is what I was getting at.  I think the address is unlikely
to change, and if (and that's a big IF) it does we can rework things.

It will reduced code and effort if you remove these from DT and
hard-code them into your driver as a #define.

Please rework accordingly.

> >>                                         compatible = "sirf,atlas7-pwrc";
> >>                                         reg = <0x3000 0x100>;
> >>                                         interrupts = <0 32 0>;
> >>                                 };
> >>
> >>                         }
> >>
> 
> -barry

-- 
Lee Jones
Linaro STMicroelectronics Landing Team Lead
Linaro.org │ Open source software for ARM SoCs
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