linux-kernel - Re: [PATCH v2 1/3] clk: meson: add DT documentation for emmc clock controller

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Date:   Thu, 12 Jul 2018 08:17:29 -0600
From:   Rob Herring <robh@...nel.org>
To:     yixun.lan@...ogic.com
Cc:     jbrunet@...libre.com, narmstrong@...libre.com,
        khilman@...libre.com, carlo@...one.org,
        Mike Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, miquel.raynal@...tlin.com,
        boris.brezillon@...tlin.com, martin.blumenstingl@...glemail.com,
        liang.yang@...ogic.com, qiufang.dai@...ogic.com,
        jian.hu@...ogic.com, linux-clk@...r.kernel.org,
        linux-amlogic@...ts.infradead.org,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        devicetree@...r.kernel.org
Subject: Re: [PATCH v2 1/3] clk: meson: add DT documentation for emmc clock controller

On Wed, Jul 11, 2018 at 8:47 PM Yixun Lan <yixun.lan@...ogic.com> wrote:
>
> Hi Rob
>
> see my comments
>
> On 07/12/18 03:43, Rob Herring wrote:
> > On Tue, Jul 10, 2018 at 04:36:56PM +0000, Yixun Lan wrote:
> >> Document the MMC sub clock controller driver, the potential consumer
> >> of this driver is MMC or NAND.
> >
> > So you all have decided to properly model this now?
> >
> Yes, ;-)
>
> >>
> >> Signed-off-by: Yixun Lan <yixun.lan@...ogic.com>
> >> ---
> >>  .../bindings/clock/amlogic,mmc-clkc.txt       | 31 +++++++++++++++++++
> >>  1 file changed, 31 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.txt
> >>
> >> diff --git a/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.txt b/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.txt
> >> new file mode 100644
> >> index 000000000000..ff6b4bf3ecf9
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/clock/amlogic,mmc-clkc.txt
> >> @@ -0,0 +1,31 @@
> >> +* Amlogic MMC Sub Clock Controller Driver
> >> +
> >> +The Amlogic MMC clock controller generates and supplies clock to support
> >> +MMC and NAND controller
> >> +
> >> +Required Properties:
> >> +
> >> +- compatible: should be:
> >> +            "amlogic,meson-gx-mmc-clkc"
> >> +            "amlogic,meson-axg-mmc-clkc"
> >> +
> >> +- #clock-cells: should be 1.
> >> +- clocks: phandles to clocks corresponding to the clock-names property
> >> +- clock-names: list of parent clock names
> >> +    - "clkin0", "clkin1"
> >> +
> >> +Parent node should have the following properties :
> >> +- compatible: "syscon", "simple-mfd, and "amlogic,meson-axg-mmc-clkc"
> >
> > You don't need "simple-mfd" and probably not syscon either. The order is
> > wrong too. Most specific first.
> >
> Ok, I will drop "simple-mfd"..
>
> but the syscon is a must, since this mmc clock model access registers
> via the regmap interface

A syscon compatible should not be the only way to get a regmap.
Removing lines 56/57 of drivers/mfd/syscon.c should be sufficient.

Why do you need a regmap in the first place? What else needs to access
this register directly? Don't you need a patch removing the clock code
from within the emmc driver? It's not even using regmap, so using
regmap here doesn't help.

Rob