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References: <20201022050445.930403-1-amstan@chromium.org> <20201021220404.v3.1.I96b8d872ec51171f19274e43e96cadc092881271@changeid>
In-Reply-To: <20201021220404.v3.1.I96b8d872ec51171f19274e43e96cadc092881271@changeid>
From:   Doug Anderson <dianders@chromium.org>
Date:   Thu, 22 Oct 2020 16:05:48 -0700
Message-ID: <CAD=FV=Vf2wfPK7CCwHi65ubPnCPWJw4Qh2nKtfC=yx7h8pvuyg@mail.gmail.com>
Subject: Re: [PATCH v3 1/3] ARM: dts: rockchip: veyron: Remove 0 point from brightness-levels
To:     Alexandru Stan <amstan@chromium.org>
Cc:     Heiko Stuebner <heiko@sntech.de>, Rob Herring <robh+dt@kernel.org>,
        Andy Gross <agross@kernel.org>,
        Bjorn Andersson <bjorn.andersson@linaro.org>,
        Thierry Reding <thierry.reding@gmail.com>,
        =?UTF-8?Q?Uwe_Kleine=2DK=C3=B6nig?= 
        <u.kleine-koenig@pengutronix.de>, Lee Jones <lee.jones@linaro.org>,
        Daniel Thompson <daniel.thompson@linaro.org>,
        Jingoo Han <jingoohan1@gmail.com>,
        Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
        Matthias Kaehlcke <mka@chromium.org>,
        Enric Balletbo i Serra <enric.balletbo@collabora.com>,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@vger.kernel.org>,
        Linux ARM <linux-arm-kernel@lists.infradead.org>,
        LKML <linux-kernel@vger.kernel.org>,
        "open list:ARM/Rockchip SoC..." <linux-rockchip@lists.infradead.org>
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Hi,

On Wed, Oct 21, 2020 at 10:05 PM Alexandru Stan <amstan@chromium.org> wrote:
>
> The extra 0 only adds one point in the userspace visible range,
> so this change is almost a noop with the current driver behavior.
>
> We don't need the 0% point, userspace seems to handle this just fine
> because it uses the bl_power property to turn off the display.
>
> Furthermore after adding "backlight: pwm_bl: Fix interpolation" patch,
> the backlight interpolation will work a little differently. So we need
> to preemptively remove the 0-3 segment since otherwise we would have a
> 252 long interpolation that would slowly go between 0 and 3, looking
> really bad in userspace. So it's almost a noop/cleanup now, but it will
> be required in the future.
>
> Signed-off-by: Alexandru Stan <amstan@chromium.org>
> ---
>
>  arch/arm/boot/dts/rk3288-veyron-jaq.dts    | 2 +-
>  arch/arm/boot/dts/rk3288-veyron-minnie.dts | 2 +-
>  arch/arm/boot/dts/rk3288-veyron-tiger.dts  | 2 +-
>  3 files changed, 3 insertions(+), 3 deletions(-)

Reviewed-by: Douglas Anderson <dianders@chromium.org>