linux-kernel - Re: [PATCH 3/5] arm64: dts: mt7622: add a property "mediatek,num-pwms" for PWM

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Message-ID: <20190117194107.wrafykdre5tugv4q@pengutronix.de>
Date:   Thu, 17 Jan 2019 20:41:07 +0100
From:   Uwe Kleine-König 
        <u.kleine-koenig@...gutronix.de>
To:     Matthias Brugger <matthias.bgg@...il.com>
Cc:     Ryder Lee <ryder.lee@...iatek.com>,
        Thierry Reding <thierry.reding@...il.com>,
        Sean Wang <sean.wang@...nel.org>,
        Weijie Gao <weijie.gao@...iatek.com>,
        linux-pwm@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH 3/5] arm64: dts: mt7622: add a property
 "mediatek,num-pwms" for PWM

Hello,

On Thu, Jan 17, 2019 at 02:00:43PM +0100, Matthias Brugger wrote:
> On 15/01/2019 21:02, Uwe Kleine-König wrote:
> > On Mon, Jan 14, 2019 at 04:21:22PM +0800, Ryder Lee wrote:
> >> diff --git a/arch/arm64/boot/dts/mediatek/mt7622.dtsi b/arch/arm64/boot/dts/mediatek/mt7622.dtsi
> >> index 8fc4aa7..ab016cf 100644
> >> --- a/arch/arm64/boot/dts/mediatek/mt7622.dtsi
> >> +++ b/arch/arm64/boot/dts/mediatek/mt7622.dtsi
> >> @@ -436,6 +436,7 @@
> >>  			 <&pericfg CLK_PERI_PWM6_PD>;
> >>  		clock-names = "top", "main", "pwm1", "pwm2", "pwm3", "pwm4",
> >>  			      "pwm5", "pwm6";
> >> +		mediatek,num-pwms = <6>;
> >>  		status = "disabled";
> > 
> > Conceptually this patch must go in before the change to the driver.
> > Otherwise the pwms are not usable with only patch 1 applied which breaks
> > bisectability.
> > 
> 
> The driver should have backwards compatibility to older DTs. So that would need
> to be fixed in the driver not in the patch order of the series.

Right you are. Bisectability is a reason to not apply the patches in the
order as is, but given that you already requested backwards
compatibility the bisectability will be fixed en passant.

Best regards
Uwe

-- 
Pengutronix e.K.                           | Uwe Kleine-König            |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |