linux-kernel - Re: [PATCH v4 00/23] soc: renesas: Add R-Car RST driver for obtaining mode pin state

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Message-ID: <CAMuHMdXA-hemOT=ZysEfettei9=HsDddGhqddkw38hwRrdeagw@mail.gmail.com>
Date:   Mon, 31 Oct 2016 09:32:55 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...eaurora.org>,
        Arnd Bergmann <arnd@...db.de>, Olof Johansson <olof@...om.net>,
        Kevin Hilman <khilman@...libre.com>
Cc:     Philipp Zabel <p.zabel@...gutronix.de>,
        Magnus Damm <magnus.damm@...il.com>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
        Linux-Renesas <linux-renesas-soc@...r.kernel.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Simon Horman <horms@...ge.net.au>
Subject: Re: [PATCH v4 00/23] soc: renesas: Add R-Car RST driver for obtaining
 mode pin state

Hi Mike, Stephen, Arnd, Olof, Kevin,

Is the merge strategy [see ##### below] OK for you?
Thanks a lot!

On Mon, Oct 31, 2016 at 9:19 AM, Simon Horman <horms@...ge.net.au> wrote:
> On Wed, Oct 26, 2016 at 02:00:24PM +0200, Geert Uytterhoeven wrote:
>> On Fri, Oct 21, 2016 at 3:17 PM, Geert Uytterhoeven
>> <geert+renesas@...der.be> wrote:
>> > Currently the R-Car Clock Pulse Generator (CPG) drivers obtains the
>> > state of the mode pins either by a call from the platform code, or
>> > directly by using a hardcoded register access. This is a bit messy, and
>> > creates a dependency between driver and platform code.
>> >
>> > This patch series converts the various Renesas R-Car clock drivers
>> > and support code from reading the mode pin states using a hardcoded
>> > register access to using a new minimalistic R-Car RST driver.
>> >
>> > All R-Car clock drivers will rely on the presence in DT of a device node
>> > for the RST module.  Backwards compatibility with old DTBs is retained
>> > only for R-Car Gen2, which has fallback code using its own private copy
>> > of rcar_gen2_read_mode_pins().
>> >
>> > After this, there is still one remaining user of
>> > rcar_gen2_read_mode_pins() left in platform code. A patch series to
>> > remove that user has already been posted, though ("[PATCH/RFT 0/4] ARM:
>> > shmobile: R-Car Gen2: Allow booting secondary CPU cores in debug mode").
>> > Since v3, the other user has been removed in commit 9f5ce39ddb8f68b3
>> > ("ARM: shmobile: rcar-gen2: Obtain extal frequency from DT").
>> >
>> > This series consists of 5 parts:
>> >   A. Patches 1 and 2 add DT bindings and driver code for the R-Car RST
>> >      driver,
>> >   B. Patches 3-11 add device nodes for the RST modules to the R-Car DTS
>> >      files,
>> >   C. Patches 12-17 convert the clock drivers to call into the new R-Car
>> >      RST driver,
>> >   D. Patches 18-20 remove passing mode pin state to the clock drivers
>> >      from the platform code,
>> >   E. Patches 21-23 remove dead code from the clock drivers.
>> >
>> > As is usually the case with moving functionality from platform code to
>> > DT, there are lots of hard dependencies:
>> >   - The DT updates in Part B can be merged as soon as the DT bindings in
>> >     Part A have been approved,
>> >   - The clock driver updates in Part C depend functionally on the driver
>> >     code in Part A, and on the DT updates in Part B,
>> >   - The board code cleanups in Part D depend on the clock driver updates
>> >     in Part C,
>> >   - The block driver cleanups in part E depend on the board code
>> >     cleanups in part D.
>> >
>> > Hence to maintain the required lockstep between SoC driver, clock
>> > drivers, shmobile platform code, and shmobile DT, I propose to queue up
>> > all patches in a single branch against v4.9-rc1, and send pull requests
>> > to both Mike/Stephen (clock) and Simon (rest).
>> >
>> > ***
>>
>> >   - Mike/Stephen/Simon/Magnus: Are you OK with the suggested merge
>> >     approach above?
>>
>> Is this OK for you?

#####

(link to the full series at
 https://groups.google.com/forum/#!topic/linux.kernel/fLSFsjOgPT8)

>>
>> I'd like to move forward with this, as this is a prerequisite for adding
>> support for new SoCs (RZ/G) without adding more copies of
>> rcar_gen2_read_mode_pins(), and removing that function from platform code
>> for good.
>
> This seems reasonable to me but likely the ARM SoC maintainers will want to
> know about this plan before it is executed.

OK, adding more people in the loop...

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds