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@xxxxxxxxxxxx> > > > > 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@xxxxxxxxxxxx> > > > Signed-off-by: Sam Shih <sam.shih@xxxxxxxxxxxx> > > > Reviewed-by: Matthias Brugger <matthias.bgg@xxxxxxxxx> > > > Acked-by: Uwe Kleine-König <u.kleine-koenig@xxxxxxxxxxxxxx> > > > --- > > > 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. I'm fine with both. num-pwms and pwm1-N is required properties for new chip, but it still have backward compatibility for old dt without num-pwms properties. > (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.) Yes, the dummy-clocks of "top", "main" is needed in old MIPS dt. We also need fixed-clock for period calculation. Best Regards, Sam
