linux-kernel - Re: [PATCH 2/2] dt-bindings: add devicetree bindings for st-pwm regulator

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Date:	Wed, 17 Sep 2014 11:16:23 -0700
From:	Doug Anderson <dianders@...omium.org>
To:	Chris Zhong <zyw@...k-chips.com>
Cc:	Heiko Stübner <heiko@...ech.de>,
	Tao Huang <huangtao@...k-chips.com>,
	Eddie Cai <cf@...k-chips.com>,
	zhangqing <zhangqing@...k-chips.com>,
	Rob Herring <robh+dt@...nel.org>,
	Pawel Moll <pawel.moll@....com>,
	Mark Rutland <mark.rutland@....com>,
	Ian Campbell <ijc+devicetree@...lion.org.uk>,
	Kumar Gala <galak@...eaurora.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"broonie@...nel.org" <broonie@...nel.org>,
	Lee Jones <lee.jones@...aro.org>
Subject: Re: [PATCH 2/2] dt-bindings: add devicetree bindings for st-pwm regulator

Chris,

On Wed, Sep 17, 2014 at 6:08 AM, Chris Zhong <zyw@...k-chips.com> wrote:
> Document the st-pwm regulator
>
> Signed-off-by: Chris Zhong <zyw@...k-chips.com>
>
> ---
>
>  .../devicetree/bindings/regulator/st-pwm.txt       |   35 ++++++++++++++++++++
>  1 file changed, 35 insertions(+)
>  create mode 100644 Documentation/devicetree/bindings/regulator/st-pwm.txt
>
> diff --git a/Documentation/devicetree/bindings/regulator/st-pwm.txt b/Documentation/devicetree/bindings/regulator/st-pwm.txt
> new file mode 100644
> index 0000000..38fec1d
> --- /dev/null
> +++ b/Documentation/devicetree/bindings/regulator/st-pwm.txt
> @@ -0,0 +1,35 @@
> +st pwm regulator bindings
> +
> +Required properties:
> +  - compatible: "pwm-regulator"

This compatible string doesn't include "st,b2105-pwm-regulator".

Should be something like:

  - compatible: Should be "pwm-regulator" to get voltage table / regulator
    period from the device tree.  Deprecated: if "st,b2105-pwm-regulator" then
    voltage table and regulator will be handled by the driver.

Assuming that everyone is OK calling "st,b2105-pwm-regulator" the
deprecated way of doing things.


> +  - pwms: OF device-tree PWM specification (see PWM binding pwm.txt)
> +  - voltage-table: voltage and duty table, include 2 merbers in each set of
> +    brackets, first one is voltage(unit: uv), the next is duty(unit: percent)
> +  - pwm-reg-period: duration (in nanoseconds) of one cycle

The voltage-table and pwm-reg-period should not be required if we're
using "st,b2105-pwm-regulator".  If someone lists both
"st,b2105-pwm-regulator" and "pwm-regulator" then I'd assume that
you'd allow them to override via the device tree but fallback to the
old hardcoded values.


> +
> +Any property defined as part of the core regulator binding defined in
> +regulator.txt can also be used.
> +
> +Example:
> +       pwm_regulator {
> +                compatible = "st,b2105-pwm-regulator;
> +                pwms = <&pwm1 0 1000000 0>;
> +
> +               voltage-table = <1114000 0>,
> +                               <1095000 10>,
> +                               <1076000 20>,
> +                               <1056000 30>,
> +                               <1036000 40>,
> +                               <1016000 50>;
> +
> +               pwm-reg-period = <8448>;
> +               regulators {
> +                       vdd_logic: pwm-regulator {
> +                               regulator-always-on;
> +                               regulator-boot-on;
> +                               regulator-min-microvolt = <1016000>;
> +                               regulator-max-microvolt = <1114000>;
> +                               regulator-name = "vdd_logic";
> +                       };
> +               };

I _think_ that the "regulators" subnode and the "pwm-regulator"
subnode are not needed at all and should be removed.  Other instances
of devices that are "just" regulators don't have it (like
fixed-regulator, gpio-regulator, etc).

I think your final example should be:

+       vdd_logic: pwm-regulator {
+                compatible = "pwm-regulator;
+                pwms = <&pwm1 0 1000000 0>;
+
+               voltage-table = <1114000 0>,
+                               <1095000 10>,
+                               <1076000 20>,
+                               <1056000 30>,
+                               <1036000 40>,
+                               <1016000 50>;
+
+               pwm-reg-period = <8448>;
+
+               regulator-always-on;
+               regulator-boot-on;
+               regulator-min-microvolt = <1016000>;
+               regulator-max-microvolt = <1114000>;
+               regulator-name = "vdd_logic";
+       };

-Doug
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