linux-kernel - [PATCH] gpiolib: of: add polarity quirk for TSC2005

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Message-ID: <ZoWXwYtwgJIxi-hD@google.com>
Date: Wed, 3 Jul 2024 11:26:09 -0700
From: Dmitry Torokhov <dmitry.torokhov@...il.com>
To: Bartosz Golaszewski <brgl@...ev.pl>
Cc: Linus Walleij <linus.walleij@...aro.org>,
	Sebastian Reichel <sre@...nel.org>,
	Pali Rohár <pali@...nel.org>,
	Pavel Machek <pavel@....cz>, linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] gpiolib: of: add polarity quirk for TSC2005

DTS for Nokia N900 incorrectly specifies "active high" polarity for
the reset line, while the chip documentation actually specifies it as
"active low".  In the past the driver fudged gpiod API and inverted
the logic internally, but it was changed in d0d89493bff8.

Fixes: d0d89493bff8 ("Input: tsc2004/5 - switch to using generic device properties")
Signed-off-by: Dmitry Torokhov <dmitry.torokhov@...il.com>
---

This was located purely by inspecting code and DTS, I have not tested
this on hardware, so copying folks who have been involved in n900 as far
as I know.

OTOH if this was indeed broken, then it was broken for ~7 years
(d0d89493bff8 went in 4.11-rc1), so maybe the best way is not to worry
about compatibility with old DTS, update
arch/arm/boot/dts/ti/omap/omap3-n900.dts in the tree and call it a day.

 drivers/gpio/gpiolib-of.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/drivers/gpio/gpiolib-of.c b/drivers/gpio/gpiolib-of.c
index 38679cf1969f..89d5e64cf68b 100644
--- a/drivers/gpio/gpiolib-of.c
+++ b/drivers/gpio/gpiolib-of.c
@@ -212,6 +212,14 @@ static void of_gpio_try_fixup_polarity(const struct device_node *np,
 		 * for the property.
 		 */
 		{ "lantiq,pci-xway",	"gpio-reset",	false },
+#endif
+#if IS_ENABLED(CONFIG_TOUCHSCREEN_TSC2005)
+		/*
+		 * DTS for Nokia N900 incorrectly specified "active high"
+		 * polarity for the reset line, while the chip actually
+		 * treats it as "active low".
+		 */
+		{ "ti,tsc2005",		"reset-gpios",	false },
 #endif
 	};
 	unsigned int i;
-- 
2.45.2.803.g4e1b14247a-goog

-- 
Dmitry