linux-kernel - Re: [PATCH v2 1/4] ARM: dts: sun8i: Add PWM pin in H3

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Date:   Thu, 1 Sep 2016 21:51:12 +0200
From:   Maxime Ripard <maxime.ripard@...e-electrons.com>
To:     Milo Kim <woogyom.kim@...il.com>
Cc:     Rob Herring <robh+dt@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Linus Walleij <linus.walleij@...aro.org>,
        Thierry Reding <thierry.reding@...il.com>,
        devicetree@...r.kernel.org, linux-gpio@...r.kernel.org,
        linux-pwm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 1/4] ARM: dts: sun8i: Add PWM pin in H3

On Thu, Sep 01, 2016 at 10:06:12PM +0900, Milo Kim wrote:
> On 09/01/2016 01:20 AM, Maxime Ripard wrote:
> >Hi Milo,
> >
> >On Wed, Aug 31, 2016 at 05:25:17PM +0900, Milo Kim wrote:
> >>H3 PA5 pin is assigned for single PWM channel.
> >>
> >>Cc: Rob Herring <robh+dt@...nel.org>
> >>Cc: Maxime Ripard <maxime.ripard@...e-electrons.com>
> >>Cc: Chen-Yu Tsai <wens@...e.org>
> >>Cc: devicetree@...r.kernel.org
> >>Cc: linux-arm-kernel@...ts.infradead.org
> >>Cc: linux-kernel@...r.kernel.org
> >>Signed-off-by: Milo Kim <woogyom.kim@...il.com>
> >>---
> >> arch/arm/boot/dts/sun8i-h3.dtsi | 7 +++++++
> >> 1 file changed, 7 insertions(+)
> >>
> >>diff --git a/arch/arm/boot/dts/sun8i-h3.dtsi b/arch/arm/boot/dts/sun8i-h3.dtsi
> >>index fdf9fdb..05d0c4b 100644
> >>--- a/arch/arm/boot/dts/sun8i-h3.dtsi
> >>+++ b/arch/arm/boot/dts/sun8i-h3.dtsi
> >>@@ -360,6 +360,13 @@
> >> 				allwinner,pull = <SUN4I_PINCTRL_NO_PULL>;
> >> 			};
> >>
> >>+			pwm0_pin_a: pwm0@0 {
> >>+				allwinner,pins = "PA5";
> >>+				allwinner,function = "pwm0";
> >>+				allwinner,drive = <SUN4I_PINCTRL_10_MA>;
> >>+				allwinner,pull = <SUN4I_PINCTRL_NO_PULL>;
> >>+			};
> >>+
> >
> >Is it used on any boards?
> >
> >If not, we have the policy of not merging the pinctrl nodes that are
> >not used by anyone to avoid bloating the DT for no particular reason.
> 
> Yes, I have. It's Nano Pi M1 which was derived from Orange Pi PC.
> The board DTS is ready to be sent out, but I'm not sure which is better.
> 
> 	a) Send new board DTS file in other patch thread
> 
> 	[PATCH v3 0/4] Add PWM feature in Allwinner H3
> 	[PATCH v3 1/4] ARM: dts: sun8i: Add PWM pin in H3
> 	..
> 	[PATCH v3 4/4] pwm: sunxi: Add H3 support
> 
> 	[PATCH] ARM: dts: sun8i: Add Nano Pi M1 support
> 
> Or
> 
> 	b) Include the DTS in next patch-set v3
> 	[PATCH v3 0/4] Add PWM feature in Allwinner H3
> 	[PATCH v3 1/4] ARM: dts: sun8i: Add PWM pin in H3
> 	[PATCH v3 2/4] ARM: dts: sun8i: Add PWM controller node in H3
> 	[PATCH v3 3/4] ARM: dts: sun8i: Add Nano Pi M1 support
> 	...

Generally speaking, I'd prefer:

[PATCH v3 1/2] pwm: sunxi: Add H3 support
[PATCH v3 2/2] ARM: dts: sun8i: Add PWM controller node in H3

(It's usually better to add support for something and then add it)

And then

[PATCH v1 1/2] ARM: dts: sun8i: Add PWM pin in H3
[PATCH v1 2/2] ARM: dts: sun8i: Add Nano Pi M1 support

However, judging from the board documentation, that pin is labelled as
PWM1/GPIOA6, which means that they don't enforce any usage on that pin
(as opposed to the pin 3 and 5 for example, which are forced to i2c0).

In such a case, we also don't enforce anything, since any user should
be able to use it for whatever he or she wants.

Maxime

-- 
Maxime Ripard, Free Electrons
Embedded Linux and Kernel engineering
http://free-electrons.com

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