[PATCH v4 3/3] arm64: dts: qcom: sc8280xp-x13s: Fix/enable touchscreen

[Bjorn Andersson]

The touchscreen present on some SKUs of Lenovo Thinkpad X13s is never
detected by Linux. Power is applied and the device is brought out of
reset using the pinconfig in DeviceTree, but the read-test in
__i2c_hid_core_probe() fails to access the device, which result in probe
being aborted.

Some users have reported success after rebinding the device.

Looking to the ACPI tables, there's a 5ms after-power and a 200ms
after-reset delay. The power-supply is shared with other components, so
this is active all the way through boot. The reset GPIO, on the other
hand, is low (reset asserted) at boot, so this is first deasserted by
the implicit application of the pinconf state.

This means the time between reset deassert and __i2c_hid_core_probe() is
significantly below the value documented in the ACPI tables.

As the I2C HID binding and driver support specifying a reset gpio,
replace the pinconf-based scheme to pull the device out of reset. Then
specify the after-reset time.

The shared power rail is currently always on, but in case this ever
change, the after-power delay is added as well, to not violate the
power-on to reset-deassert timing requirement.

Fixes: 32c231385ed4 ("arm64: dts: qcom: sc8280xp: add Lenovo Thinkpad X13s devicetree")
Tested-by: Daniel Thompson <daniel.thompson@xxxxxxxxxx>
Reviewed-by: Johan Hovold <johan+linaro@xxxxxxxxxx>
Signed-off-by: Bjorn Andersson <quic_bjorande@xxxxxxxxxxx>
---
 arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
index def3976bd5bb..33731b95ad51 100644
--- a/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
+++ b/arch/arm64/boot/dts/qcom/sc8280xp-lenovo-thinkpad-x13s.dts
@@ -620,7 +620,6 @@ &i2c4 {
 
 	status = "okay";
 
-	/* FIXME: verify */
 	touchscreen@10 {
 		compatible = "hid-over-i2c";
 		reg = <0x10>;
@@ -630,6 +629,11 @@ touchscreen@10 {
 		vdd-supply = <&vreg_misc_3p3>;
 		vddl-supply = <&vreg_s10b>;
 
+		reset-gpios = <&tlmm 99 GPIO_ACTIVE_LOW>;
+
+		post-power-on-delay-ms = <5>;
+		post-reset-deassert-delay-ms = <200>;
+
 		pinctrl-names = "default";
 		pinctrl-0 = <&ts0_default>;
 	};
@@ -1450,7 +1454,6 @@ int-n-pins {
 		reset-n-pins {
 			pins = "gpio99";
 			function = "gpio";
-			output-high;
 			drive-strength = <16>;
 		};
 	};

-- 
2.25.1