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Message-ID: <Y5Jxn01EzEZ8fE1G@google.com>
Date: Thu, 8 Dec 2022 23:22:07 +0000
From: Matthias Kaehlcke <mka@...omium.org>
To: Douglas Anderson <dianders@...omium.org>
Cc: Bjorn Andersson <andersson@...nel.org>,
Dmitry Torokhov <dmitry.torokhov@...il.com>,
swboyd@...omium.org, linux-arm-msm@...r.kernel.org,
linux-input@...r.kernel.org,
Yunlong Jia <ecs.beijing2022@...il.com>,
Konrad Dybcio <konrad.dybcio@...aro.org>,
Andy Gross <agross@...nel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
Rob Herring <robh+dt@...nel.org>, devicetree@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/5] arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l
drive strength
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@...omium.org>
Reviewed-by: Matthias Kaehlcke <mka@...omium.org>
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