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

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Date:	Tue, 29 Sep 2015 09:55:05 +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 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?

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