linux-kernel - Re: [PATCH 2/3] mfd: db8500-prcmu: Fetch the PRCMU TCDM base address from Device Tree

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Message-ID: <20130326081704.GB11734@gmail.com>
Date:	Tue, 26 Mar 2013 08:17:04 +0000
From:	Lee Jones <lee.jones@...aro.org>
To:	Linus Walleij <linus.walleij@...aro.org>
Cc:	devicetree-discuss@...ts.ozlabs.org, Arnd Bergmann <arnd@...db.de>,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linus.walleij@...ricsson.com
Subject: Re: [PATCH 2/3] mfd: db8500-prcmu: Fetch the PRCMU TCDM base address
 from Device Tree

On Mon, 25 Mar 2013, Linus Walleij wrote:

> On Mon, Mar 25, 2013 at 5:46 PM, Lee Jones <lee.jones@...aro.org> wrote:
> 
> >> >         res = platform_get_resource_byname(pdev, IORESOURCE_MEM,
> >> >                                            "prcmu-tcpm");
> >> >         if (!res) {
> >> > -               dev_err(&pdev->dev,
> >> > -                       "Error: no prcmu tcpm memory region provided\n");
> >> > -               return;
> >> > -       }
> >> > -       tcpm_base = ioremap(res->start, resource_size(res));
> >> > +               if (np) {
> >> > +                       tcpm_np = of_find_node_by_name(np->parent,
> >> > +                                                      "prcmu-tcpm-per4");
> >> > +                       if (!tcpm_np) {
> >> > +                               dev_err(&pdev->dev,
> >> > +                                       "no prcmu tcpm mem region provided\n");
> >> > +                               return;
> >> > +                       }
> >> > +                       tcpm_base = of_iomap(tcpm_np, 0);
> >> > +               }
> >> > +       } else
> >> > +               tcpm_base = ioremap(res->start, resource_size(res));
> >> > +
> >>
> >> Why don't you just add these extra registers to the prcmu node itself like
> >>
> >> diff --git a/arch/arm/boot/dts/dbx5x0.dtsi b/arch/arm/boot/dts/dbx5x0.dtsi
> >> index 9de9309..6ee6c31 100644
> >> --- a/arch/arm/boot/dts/dbx5x0.dtsi
> >> +++ b/arch/arm/boot/dts/dbx5x0.dtsi
> >> @@ -191,8 +191,8 @@
> >>
> >>               prcmu: prcmu@...57000 {
> >>                       compatible = "stericsson,db8500-prcmu";
> >> -                     reg = <0x80157000 0x1000>;
> >> -                     reg-names = "prcmu";
> >> +                     reg = <0x80157000 0x1000>, <0x801b0000 0x1000>, <0x801b8000 0x1000>;
> >> +                     reg-names = "prcmu", "prcmu-tcpm", "prcmu-tcdm-per4";
> >>                       interrupts = <0 47 0x4>;
> >>                       #address-cells = <1>;
> >>                       #size-cells = <1>;
> >>
> >>
> >> and document those in the prcmu binding?
> >>
> >> That would keep the code simpler and the same for both cases.
> >
> > I'm not sure you can. These addresses differ from platform to
> > platform, so I'd need to provide the base PRCMU address in
> > dbx5x0.dtsi, then the other two in the dts files. Can you do that?
> 
> Better ask on devicetree-discuss.
> 
> What it reflects are differences between SoC:s, so I think the
> right solution is to split it in a three-layer cake:
> 
> dbx5x0.dtsi -> included by
> db8500.dtsi -> included by
> snowball/hrefv60plus.dts
> 
> dbx5x0.dtsi -> included by
> dbx540.dtsi -> included by
> ccu9540/ccu8540.dts
> 
> Here you may insert the reg property into the node at the
> db8500.dtsi or dbx540.dtsi layer.

It's easy done, if that's the right way.

> If you prefer I can cook a patch...

... and I'm fine to do it.

[5 mins later]

Hmm... it appears that in STE's kernel, the same address is used for
all SoCs: 

  #define U8500_PRCMU_TCDM_BASE    (U8500_PER4_BASE + 0x68000)

However, in Mainline there is another definition:

  #define U9540_PRCMU_TCDM_BASE    (U8500_PER4_BASE + 0x6A000)

... which doesn't seem to be in use anywhere - even for the u9540.

What's the deal big-man?

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