Commit 9506a366 authored by Douglas Anderson's avatar Douglas Anderson Committed by Bjorn Andersson
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arm64: dts: qcom: sc7180: Bump up trogdor ts_reset_l drive strength 



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: default avatarDouglas Anderson <dianders@chromium.org>
Reviewed-by: default avatarMatthias Kaehlcke <mka@chromium.org>
Reviewed-by: default avatarKonrad Dybcio <konrad.dybcio@linaro.org>
Signed-off-by: default avatarBjorn Andersson <andersson@kernel.org>
Link: https://lore.kernel.org/r/20221209091234.v3.1.I39c387f1e3176fcf340039ec12d54047de9f8526@changeid
parent 1c170714

arch/arm64/boot/dts/qcom/sc7180-trogdor.dtsi

+9 −1
Original line number Diff line number Diff line
@@ -1394,7 +1394,15 @@ ap_spi_fp: &spi10 { 
		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 {