[PATCH] gpio: pca953x: use regmap_update_bits() to improve efficiency

[PATCH] gpio: pca953x: use regmap_update_bits() to improve efficiency

[Hugo Villeneuve]

From: Hugo Villeneuve <hvilleneuve@dimonoff.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@dimonoff.com>
---
 drivers/gpio/gpio-pca953x.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/drivers/gpio/gpio-pca953x.c b/drivers/gpio/gpio-pca953x.c
index e80a96f397885..34dd5b4a6b299 100644
--- a/drivers/gpio/gpio-pca953x.c
+++ b/drivers/gpio/gpio-pca953x.c
@@ -533,7 +533,7 @@ static int pca953x_gpio_direction_input(struct gpio_chip *gc, unsigned off)
 
 	guard(mutex)(&chip->i2c_lock);
 
-	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,
@@ -548,12 +548,12 @@ 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;
 
 	/* then direction */
-	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)
@@ -581,7 +581,7 @@ 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)
@@ -658,9 +658,9 @@ 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)
@@ -668,9 +668,9 @@ 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: 733923397fd95405a48f165c9b1fbc8c4b0a4681
-- 
2.39.5

Re: [PATCH] gpio: pca953x: use regmap_update_bits() to improve efficiency

[Bartosz Golaszewski]

On Wed, Jul 9, 2025 at 10:10 PM Hugo Villeneuve <hugo@hugovil.com> wrote:
>
> From: Hugo Villeneuve <hvilleneuve@dimonoff.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@dimonoff.com>
> ---

Nice! Can you rebase it on top of gpio/for-next, it doesn't apply
after recent changes to the driver.

Thanks!
Bart

Re: [PATCH] gpio: pca953x: use regmap_update_bits() to improve efficiency

[Hugo Villeneuve]

On Fri, 11 Jul 2025 12:22:40 +0200
Bartosz Golaszewski <brgl@bgdev.pl> wrote:

Hi Bart,


> On Wed, Jul 9, 2025 at 10:10 PM Hugo Villeneuve <hugo@hugovil.com> wrote:
> >
> > From: Hugo Villeneuve <hvilleneuve@dimonoff.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@dimonoff.com>
> > ---
> 
> Nice! Can you rebase it on top of gpio/for-next, it doesn't apply
> after recent changes to the driver.

Sure, I will send a V2 shortly.

Hugo.