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Date:   Thu, 8 Dec 2022 23:22:07 +0000
From:   Matthias Kaehlcke <mka@chromium.org>
To:     Douglas Anderson <dianders@chromium.org>
Cc:     Bjorn Andersson <andersson@kernel.org>,
        Dmitry Torokhov <dmitry.torokhov@gmail.com>,
        swboyd@chromium.org, linux-arm-msm@vger.kernel.org,
        linux-input@vger.kernel.org,
        Yunlong Jia <ecs.beijing2022@gmail.com>,
        Konrad Dybcio <konrad.dybcio@linaro.org>,
        Andy Gross <agross@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Rob Herring <robh+dt@kernel.org>, devicetree@vger.kernel.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/5] arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l
 drive strength
Message-ID: <Y5Jxn01EzEZ8fE1G@google.com>
References: <20221208192006.1070898-1-dianders@chromium.org>
 <20221208111910.1.I39c387f1e3176fcf340039ec12d54047de9f8526@changeid>
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On Thu, Dec 08, 2022 at 11:20:02AM -0800, Douglas Anderson wrote:
> On at least one board (pazquel360) the reset line for the touchscreen
> was scoped and found to take almost 2 ms to fall when we drove it
> low. This wasn't great because the Linux driver for the touchscreen
> (the elants_i2c driver) thinks it can do a 500 us reset pulse. If we
> bump the drive strength to 8 mA then the reset line went down in ~421
> us.
> 
> NOTE: we could apply this fix just for pazquel360, but:
> * Probably other trogdor devices have similar timings and it's just
>   that nobody has noticed it before.
> * There are other trogdor boards using the same elan driver that tries
>   to do 500 us reset pulses.
> * Bumping the drive strength to 8mA across the board won't hurt. This
>   isn't a high speed signal or anything.
> 
> Signed-off-by: Douglas Anderson <dianders@chromium.org>

Reviewed-by: Matthias Kaehlcke <mka@chromium.org>