linux-kernel - Re: [PATCH v4 03/11] iio: accel: adxl313: make use of regmap cache

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Message-ID: <20250608162215.0d1789d0@jic23-huawei>
Date: Sun, 8 Jun 2025 16:22:15 +0100
From: Jonathan Cameron <jic23@...nel.org>
To: Lothar Rubusch <l.rubusch@...il.com>
Cc: dlechner@...libre.com, nuno.sa@...log.com, andy@...nel.org,
 corbet@....net, lucas.p.stankus@...il.com, lars@...afoo.de,
 Michael.Hennerich@...log.com, bagasdotme@...il.com,
 linux-iio@...r.kernel.org, linux-doc@...r.kernel.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH v4 03/11] iio: accel: adxl313: make use of regmap cache

On Sun,  1 Jun 2025 17:21:31 +0000
Lothar Rubusch <l.rubusch@...il.com> wrote:

> Setup regmap cache to cache register configuration. This is a preparatory
> step for follow up patches. Using cached settings will help at inerrupt
> handling, to generate activity and inactivity events.

The regmap cache will reduce traffic to the device for things like reading
back sampling frequency, so no need to justify this patch with 'future'
stuff.  Justify it with current.   I've applied with the description of
simply

"Setup regmap cache to cache register configuration, reducing bus traffic
for repeated accesses to non volatile registers."

> 
> Signed-off-by: Lothar Rubusch <l.rubusch@...il.com>
> ---
>  drivers/iio/accel/adxl313.h      |  2 ++
>  drivers/iio/accel/adxl313_core.c | 17 +++++++++++++++++
>  drivers/iio/accel/adxl313_i2c.c  |  6 ++++++
>  drivers/iio/accel/adxl313_spi.c  |  6 ++++++
>  4 files changed, 31 insertions(+)
> 
> diff --git a/drivers/iio/accel/adxl313.h b/drivers/iio/accel/adxl313.h
> index 72f624af4686..fc937bdf83b6 100644
> --- a/drivers/iio/accel/adxl313.h
> +++ b/drivers/iio/accel/adxl313.h
> @@ -54,6 +54,8 @@ extern const struct regmap_access_table adxl312_writable_regs_table;
>  extern const struct regmap_access_table adxl313_writable_regs_table;
>  extern const struct regmap_access_table adxl314_writable_regs_table;
>  
> +bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg);
> +
>  enum adxl313_device_type {
>  	ADXL312,
>  	ADXL313,
> diff --git a/drivers/iio/accel/adxl313_core.c b/drivers/iio/accel/adxl313_core.c
> index 06a771bb4726..0c893c286017 100644
> --- a/drivers/iio/accel/adxl313_core.c
> +++ b/drivers/iio/accel/adxl313_core.c
> @@ -46,6 +46,23 @@ const struct regmap_access_table adxl314_readable_regs_table = {
>  };
>  EXPORT_SYMBOL_NS_GPL(adxl314_readable_regs_table, IIO_ADXL313);
>  
> +bool adxl313_is_volatile_reg(struct device *dev, unsigned int reg)
> +{
> +	switch (reg) {
> +	case ADXL313_REG_DATA_AXIS(0):
> +	case ADXL313_REG_DATA_AXIS(1):
> +	case ADXL313_REG_DATA_AXIS(2):
> +	case ADXL313_REG_DATA_AXIS(3):
> +	case ADXL313_REG_DATA_AXIS(4):
> +	case ADXL313_REG_DATA_AXIS(5):
> +	case ADXL313_REG_FIFO_STATUS:
> +		return true;
> +	default:
> +		return false;
> +	}
> +}
> +EXPORT_SYMBOL_NS_GPL(adxl313_is_volatile_reg, "IIO_ADXL313");
> +
>  static int adxl312_check_id(struct device *dev,
>  			    struct adxl313_data *data)
>  {
> diff --git a/drivers/iio/accel/adxl313_i2c.c b/drivers/iio/accel/adxl313_i2c.c
> index a4cf0cf2c5aa..e8636e8ab14f 100644
> --- a/drivers/iio/accel/adxl313_i2c.c
> +++ b/drivers/iio/accel/adxl313_i2c.c
> @@ -21,6 +21,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
>  		.rd_table	= &adxl312_readable_regs_table,
>  		.wr_table	= &adxl312_writable_regs_table,
>  		.max_register	= 0x39,
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  	[ADXL313] = {
>  		.reg_bits	= 8,
> @@ -28,6 +30,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
>  		.rd_table	= &adxl313_readable_regs_table,
>  		.wr_table	= &adxl313_writable_regs_table,
>  		.max_register	= 0x39,
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  	[ADXL314] = {
>  		.reg_bits	= 8,
> @@ -35,6 +39,8 @@ static const struct regmap_config adxl31x_i2c_regmap_config[] = {
>  		.rd_table	= &adxl314_readable_regs_table,
>  		.wr_table	= &adxl314_writable_regs_table,
>  		.max_register	= 0x39,
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  };
>  
> diff --git a/drivers/iio/accel/adxl313_spi.c b/drivers/iio/accel/adxl313_spi.c
> index 9a16b40bff34..68e323e81aeb 100644
> --- a/drivers/iio/accel/adxl313_spi.c
> +++ b/drivers/iio/accel/adxl313_spi.c
> @@ -24,6 +24,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
>  		.max_register	= 0x39,
>  		/* Setting bits 7 and 6 enables multiple-byte read */
>  		.read_flag_mask	= BIT(7) | BIT(6),
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  	[ADXL313] = {
>  		.reg_bits	= 8,
> @@ -33,6 +35,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
>  		.max_register	= 0x39,
>  		/* Setting bits 7 and 6 enables multiple-byte read */
>  		.read_flag_mask	= BIT(7) | BIT(6),
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  	[ADXL314] = {
>  		.reg_bits	= 8,
> @@ -42,6 +46,8 @@ static const struct regmap_config adxl31x_spi_regmap_config[] = {
>  		.max_register	= 0x39,
>  		/* Setting bits 7 and 6 enables multiple-byte read */
>  		.read_flag_mask	= BIT(7) | BIT(6),
> +		.volatile_reg	= adxl313_is_volatile_reg,
> +		.cache_type	= REGCACHE_MAPLE,
>  	},
>  };
>