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arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l drive strength

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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>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: Bjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221209091234.v3.1.I39c387f1e3176fcf340039ec12d54047de9f8526@changeid
This commit is contained in:
Douglas Anderson 2022-12-09 09:12:37 -08:00 committed by Bjorn Andersson
parent 1c17071449
commit 9506a36612
1 changed files with 9 additions and 1 deletions
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10
arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi
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@ -1394,7 +1394,15 @@ ts_reset_l: ts-reset-l-state {
pins = "gpio8";
function = "gpio";
bias-disable;
drive-strength = <2>;
/*
* The reset GPIO to the touchscreen takes almost 2ms to drop
* at the default drive strength. When we bump it up to 8mA it
* falls in under 500us. We want this to be fast since the Elan
* datasheet (and any drivers written based on it) talk about using
* a 500 us reset pulse.
*/
drive-strength = <8>;
};
sdc1_on: sdc1-on-state {