[PATCH/RFC] ARM: shmobile: dts: Add common file for MSIOF1

[Magnus Damm]

Hi Simon,

On Fri, Nov 21, 2014 at 1:59 PM, Simon Horman <horms at verge.net.au> wrote:
> On Fri, Nov 21, 2014 at 01:45:32PM +0900, Magnus Damm wrote:
>> Hi Simon,
>>
>> On Fri, Nov 21, 2014 at 1:27 PM, Simon Horman
>> <horms+renesas at verge.net.au> wrote:
>> > From: Hisashi Nakamura <hisashi.nakamura.ak at renesas.com>
>> >
>> > The R-Car Gen 2 SoCs have MSIOF1 interfaces however they
>> > are not exposed on any boards currently supported in mainline.
>>
>> Ok, but that's the same as many other devices on R-Car Gen2 SoCs no?
>> Basically the SoC contains a hardware block but it is not used on the
>> actual board. I wonder what made MSIOF1 a target for sudden code
>> consolidation?
>>
>> > The purpose of r8a77xx-msiof1.dtsi is to be included
>> > in a dts file if MSIOF1 is exposed by some means.
>>
>> Judging by the file name this seems to be a board specific property
>> made generic somehow.
>
> Yes, it is board stuff not SoC stuff.
>
>>
>> > Signed-off-by: Hisashi Nakamura <hisashi.nakamura.ak at renesas.com>
>> > [horms: Reworked into a separate dtsi file]
>> > Signed-off-by: Simon Horman <horms+renesas at verge.net.au>
>>
>> [snip]
>>
>> > +&pfc {
>> > +       msiof1_pins: spi2 {
>> > +               renesas,groups = "msiof1_clk_c", "msiof1_sync_c", "msiof1_rx_c",
>> > +                                "msiof1_tx_c";
>> > +               renesas,function = "msiof1";
>> > +       };
>> > +};
>> > +
>> > +&msiof1 {
>> > +       pinctrl-0 = <&msiof1_pins>;
>> > +       pinctrl-names = "default";
>> > +
>> > +       status = "okay";
>> > +};
>>
>> The DTS above only works on boards that are using the "C" set of pins
>> for the MSIOF1. Other configurations will not work. It also assumes
>> that all SoC code is using the same strings for the PFC which may or
>> may not be true.
>>
>> Does some common policy for the Linux kernel exist about how to break
>> out board specific device support in DTS? If so we should follow it.
>>
>> If not, from my conservative view point this patch looks like over
>> doing code sharing with increased overhead and no apparent upside
>> except more complex dependencies.
>
> Perhaps it would be best just to drop it.
>
> The patch that this code was based on illustrates how to enable
> MSIOF1 on the koelsch. People can find that and use it if they
> wish to use MSIOF1.

Thanks, that sounds like a good plan to me.

/ magnus