linux-kernel - Re: [PATCH v3 5/5] ARM: dts: rockchip: set PWM delay backlight settings for Minnie

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Message-ID: <20170720081038.GD13103@amd>
Date:   Thu, 20 Jul 2017 10:10:38 +0200
From:   Pavel Machek <pavel@....cz>
To:     Enric Balletbo i Serra <enric.balletbo@...labora.com>
Cc:     Thierry Reding <thierry.reding@...il.com>,
        Lee Jones <lee.jones@...aro.org>,
        Daniel Thompson <daniel.thompson@...aro.org>,
        Jingoo Han <jingoohan1@...il.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@...sung.com>,
        Rob Herring <robh+dt@...nel.org>,
        Richard Purdie <rpurdie@...ys.net>,
        Jacek Anaszewski <jacek.anaszewski@...il.com>,
        Heiko Stuebner <heiko@...ech.de>, linux-pwm@...r.kernel.org,
        linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        groeck@...omium.org, linux-rockchip@...ts.infradead.org
Subject: Re: [PATCH v3 5/5] ARM: dts: rockchip: set PWM delay backlight
 settings for Minnie

On Mon 2017-07-17 23:28:11, Enric Balletbo i Serra wrote:
> The minnie devices comes with an AUO B101EAN01 panel which is different
> from default veyron devices, thus the power on/off timing sequence is
> slightly different. The datasheet specifies a pwm delay of 200 ms, so
> update the PMW delay proprieties accordingly.

Wait a wait a moment!

> --- a/arch/arm/boot/dts/rk3288-veyron-minnie.dts
> +++ b/arch/arm/boot/dts/rk3288-veyron-minnie.dts
> @@ -123,6 +123,8 @@
>  			240 241 242 243 244 245 246 247
>  			248 249 250 251 252 253 254 255>;
>  	power-supply = <&backlight_regulator>;
> +	post-pwm-on-delay-us = <20000>;

-us = <20 000>;

This is not 200 msec.

Plus, it is quite anti-social to do udelay(200 000).

Plus, it is very anti-socifal to use udelay_range(200msec,
400msec).

Whoever told you udelay_range is good thing to use -- it is not, and
it is certainly not worth making user wait 200msec more!

									Pavel
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html

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