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References: <20201022050445.930403-1-amstan@chromium.org> <20201021220404.v3.2.Ie4d84af5a85e8dcb8f575845518fa39f324a827d@changeid>
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From:   Doug Anderson <dianders@chromium.org>
Date:   Thu, 22 Oct 2020 16:07:58 -0700
Message-ID: <CAD=FV=VeRs=EzBoQkVNVYnrEmUAwV0B-zKtYeS9s80TpEjPmgg@mail.gmail.com>
Subject: Re: [PATCH v3 2/3] arm64: dts: qcom: trogdor: Add 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-msm <linux-arm-msm@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
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Hi,

On Wed, Oct 21, 2020 at 10:05 PM Alexandru Stan <amstan@chromium.org> wrote:
>
> We want userspace to represent the human perceived brightness.
> Since the led drivers and the leds themselves don't have a
> linear response to the value we give them in terms of perceived
> brightness, we'll bake the curve into the dts.
>
> The panel also doesn't have a good response under 5%, so we'll avoid
> sending it anything lower than that.
>
> Note: Ideally this patch should be coupled with the driver change from
> "backlight: pwm_bl: Fix interpolation", but it can work without it,
> without looking too ugly.
>
> Signed-off-by: Alexandru Stan <amstan@chromium.org>
> ---
>
>  arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi | 9 +++++++++
>  1 file changed, 9 insertions(+)

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