linux-kernel - [PATCH v2] gpio: pca953x: use regmap_update

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Message-Id: <20250714133730.6353-1-hugo@hugovil.com>
Date: Mon, 14 Jul 2025 09:37:30 -0400
From: Hugo Villeneuve <hugo@...ovil.com>
To: Linus Walleij <linus.walleij@...aro.org>,
	Bartosz Golaszewski <brgl@...ev.pl>
Cc: hugo@...ovil.com,
	Hugo Villeneuve <hvilleneuve@...onoff.com>,
	linux-gpio@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v2] gpio: pca953x: use regmap_update_bits() to improve efficiency

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

Using regmap_update_bits() allows to reduce the number of I2C transfers
when updating bits that haven't changed on non-volatile registers.

For example on a PCAL6416, when changing a GPIO direction from input to
output, the number of I2C transfers can be reduced from 4 to just 1 if
the pull resistors configuration hasn't changed and the output value
is the same as before.

Signed-off-by: Hugo Villeneuve <hvilleneuve@...onoff.com>
---
V1 -> V2: rebase on gpio/for-next
---
 drivers/gpio/gpio-pca953x.c | 20 ++++++++++----------
 1 file changed, 10 insertions(+), 10 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index f5184860bd89f..169877e59da9d 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -611,9 +611,9 @@ static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
 	guard(mutex)(&chip->i2c_lock);
 
 	if (PCA_CHIP_TYPE(chip->driver_data) == TCA6418_TYPE)
-		return regmap_write_bits(chip->regmap, dirreg, bit, 0);
+		return regmap_update_bits(chip->regmap, dirreg, bit, 0);
 
-	return regmap_write_bits(chip->regmap, dirreg, bit, bit);
+	return regmap_update_bits(chip->regmap, dirreg, bit, bit);
 }
 
 static int pca953x_gpio_direction_output(struct gpio_chip *gc,
@@ -628,7 +628,7 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,
 	guard(mutex)(&chip->i2c_lock);
 
 	/* set output level */
-	ret = regmap_write_bits(chip->regmap, outreg, bit, val ? bit : 0);
+	ret = regmap_update_bits(chip->regmap, outreg, bit, val ? bit : 0);
 	if (ret)
 		return ret;
 
@@ -637,9 +637,9 @@ static int pca953x_gpio_direction_output(struct gpio_chip *gc,
 	 * (in/out logic is inverted on TCA6418)
 	 */
 	if (PCA_CHIP_TYPE(chip->driver_data) == TCA6418_TYPE)
-		return regmap_write_bits(chip->regmap, dirreg, bit, bit);
+		return regmap_update_bits(chip->regmap, dirreg, bit, bit);
 
-	return regmap_write_bits(chip->regmap, dirreg, bit, 0);
+	return regmap_update_bits(chip->regmap, dirreg, bit, 0);
 }
 
 static int pca953x_gpio_get_value(struct gpio_chip *gc, unsigned off)
@@ -667,7 +667,7 @@ static int pca953x_gpio_set_value(struct gpio_chip *gc, unsigned int off,
 
 	guard(mutex)(&chip->i2c_lock);
 
-	return regmap_write_bits(chip->regmap, outreg, bit, val ? bit : 0);
+	return regmap_update_bits(chip->regmap, outreg, bit, val ? bit : 0);
 }
 
 static int pca953x_gpio_get_direction(struct gpio_chip *gc, unsigned off)
@@ -751,9 +751,9 @@ static int pca953x_gpio_set_pull_up_down(struct pca953x_chip *chip,
 
 	/* Configure pull-up/pull-down */
 	if (param == PIN_CONFIG_BIAS_PULL_UP)
-		ret = regmap_write_bits(chip->regmap, pull_sel_reg, bit, bit);
+		ret = regmap_update_bits(chip->regmap, pull_sel_reg, bit, bit);
 	else if (param == PIN_CONFIG_BIAS_PULL_DOWN)
-		ret = regmap_write_bits(chip->regmap, pull_sel_reg, bit, 0);
+		ret = regmap_update_bits(chip->regmap, pull_sel_reg, bit, 0);
 	else
 		ret = 0;
 	if (ret)
@@ -761,9 +761,9 @@ static int pca953x_gpio_set_pull_up_down(struct pca953x_chip *chip,
 
 	/* Disable/Enable pull-up/pull-down */
 	if (param == PIN_CONFIG_BIAS_DISABLE)
-		return regmap_write_bits(chip->regmap, pull_en_reg, bit, 0);
+		return regmap_update_bits(chip->regmap, pull_en_reg, bit, 0);
 	else
-		return regmap_write_bits(chip->regmap, pull_en_reg, bit, bit);
+		return regmap_update_bits(chip->regmap, pull_en_reg, bit, bit);
 }
 
 static int pca953x_gpio_set_config(struct gpio_chip *gc, unsigned int offset,

base-commit: e502df58b5e3767c00e887744b6eff43b7fde3ea
-- 
2.39.5