linux-kernel - [PATCH] Input: cyttsp5 - ensure minimum reset pulse width

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Message-Id: <20250204190100.2210863-1-hugo@hugovil.com>
Date: Tue,  4 Feb 2025 14:01:00 -0500
From: Hugo Villeneuve <hugo@...ovil.com>
To: Linus Walleij <linus.walleij@...aro.org>,
	Dmitry Torokhov <dmitry.torokhov@...il.com>,
	Alistair Francis <alistair@...stair23.me>,
	Maxime Ripard <mripard@...nel.org>,
	Mylène Josserand <mylene.josserand@...tlin.com>
Cc: hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	stable@...r.kernel.org,
	linux-input@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH] Input: cyttsp5 - ensure minimum reset pulse width

From: Hugo Villeneuve <hvilleneuve@...onoff.com>

The current reset pulse width is measured to be 5us on a
Renesas RZ/G2L SOM. The manufacturer's minimum reset pulse width is
specified as 10us.

Extend reset pulse width to make sure it is long enough on all platforms.

Also reword confusing comments about reset pin assertion.

Fixes: 5b0c03e24a06 ("Input: Add driver for Cypress Generation 5 touchscreen")
Cc: <stable@...r.kernel.org>
Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
 drivers/input/touchscreen/cyttsp5.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/input/touchscreen/cyttsp5.c b/drivers/input/touchscreen/cyttsp5.c
index eafe5a9b8964..bb09e84d0e92 100644
--- a/drivers/input/touchscreen/cyttsp5.c
+++ b/drivers/input/touchscreen/cyttsp5.c
@@ -870,13 +870,16 @@ static int cyttsp5_probe(struct device *dev, struct regmap *regmap, int irq,
 	ts->input->phys = ts->phys;
 	input_set_drvdata(ts->input, ts);
 
-	/* Reset the gpio to be in a reset state */
+	/* Assert gpio to be in a reset state */
 	ts->reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(ts->reset_gpio)) {
 		error = PTR_ERR(ts->reset_gpio);
 		dev_err(dev, "Failed to request reset gpio, error %d\n", error);
 		return error;
 	}
+
+	fsleep(1000); /* Ensure long-enough reset pulse (minimum 10us). */
+
 	gpiod_set_value_cansleep(ts->reset_gpio, 0);
 
 	/* Need a delay to have device up */

base-commit: 0de63bb7d91975e73338300a57c54b93d3cc151c
-- 
2.39.5