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    SubjectRe: [PATCH v5 07/13] dt-bindings: pwm: add a property "num-pwms"
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    On Mon, 2019-09-02 at 18:04 +0200, Uwe Kleine-König wrote:
    > On Tue, Aug 27, 2019 at 01:39:24PM -0500, Rob Herring wrote:
    > > On Thu, Aug 22, 2019 at 02:58:37PM +0800, Sam Shih wrote:
    > > > From: Ryder Lee <ryder.lee@mediatek.com>
    > >
    > > The subject should indicate this is for Mediatek.
    > >
    > > >
    > > > This adds a property "num-pwms" in example so that we could
    > > > specify the number of PWM channels via device tree.
    > > >
    > > > Signed-off-by: Ryder Lee <ryder.lee@mediatek.com>
    > > > Signed-off-by: Sam Shih <sam.shih@mediatek.com>
    > > > Reviewed-by: Matthias Brugger <matthias.bgg@gmail.com>
    > > > Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
    > > > ---
    > > > Changes since v5:
    > > > - Add an Acked-by tag
    > > > - This file is original v4 patch 5/10
    > > > (https://patchwork.kernel.org/patch/11102577/)
    > > >
    > > > Change-Id: I429048afeffa96f3f14533910efe242f88776043
    > > > ---
    > > > Documentation/devicetree/bindings/pwm/pwm-mediatek.txt | 7 ++++---
    > > > 1 file changed, 4 insertions(+), 3 deletions(-)
    > > >
    > > > diff --git a/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt b/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt
    > > > index 991728cb46cb..ea95b490a913 100644
    > > > --- a/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt
    > > > +++ b/Documentation/devicetree/bindings/pwm/pwm-mediatek.txt
    > > > @@ -14,12 +14,12 @@ Required properties:
    > > > has no clocks
    > > > - "top": the top clock generator
    > > > - "main": clock used by the PWM core
    > > > - - "pwm1-8": the eight per PWM clocks for mt2712
    > > > - - "pwm1-6": the six per PWM clocks for mt7622
    > > > - - "pwm1-5": the five per PWM clocks for mt7623
    > > > + - "pwm1-N": the PWM clocks for each channel
    > > > + where N starting from 1 to the maximum number of PWM channels
    > >
    > > Once converted to schema, you are going to be back to listing them out.
    > >
    > > > - pinctrl-names: Must contain a "default" entry.
    > > > - pinctrl-0: One property must exist for each entry in pinctrl-names.
    > > > See pinctrl/pinctrl-bindings.txt for details of the property values.
    > > > + - num-pwms: the number of PWM channels.
    > >
    > > You can't add new required properties without breaking compatibility.
    > >
    > > You already have to imply the number of channels from the compatible (or
    > > number of clocks) and you have to keep doing so to maintain
    > > compatibility, so why not just keep doing that for new chips?
    >
    > This was a suggestion by me. The driver still handles compatibility
    > (i.e. falls back to the number of PWMs that was implied by the
    > compatible before). Given that there are various drivers that all solve
    > the same problem (i.e. different variants with different number of PWMs)
    > I thought it would be a good idea to introduce a property in the device
    > tree that specifies this number.
    >
    > Only for newly introduced compatibles the num-pwms property is really
    > required. Differentiating the ones that need it and the ones that don't
    > seems over-engineered to me.
    >
    > (BTW, using the number of clks doesn't really work because there are
    > also some variants without clocks. It is still under discussion if in
    > this case dummy-clocks should be provided IIRC.)
    >
    > Best regards
    > Uwe
    >


    Any conclusions ?

    just a friendly reminder :)


    regards Sam


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