Re: [PATCH v2] iio: bmi323: peripheral in lowest power state on suspend

[Jonathan Cameron <jic23@kernel.org>]

On Sun, 18 Aug 2024 17:09:23 +0200
Denis Benato <benato.denis96@gmail.com> wrote:

> The bmi323 is mounted on some devices that are powered
> by an internal battery: help in reducing system overall power drain
> while the system is in s2idle or the imu driver is not loaded
> by resetting it in its lowest power draining state.
> 
> Signed-off-by: Denis Benato <benato.denis96@gmail.com>
> ---
>  drivers/iio/imu/bmi323/bmi323_core.c | 225 ++++++++++++++++++++++++++-
>  1 file changed, 223 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/iio/imu/bmi323/bmi323_core.c b/drivers/iio/imu/bmi323/bmi323_core.c
> index 4b2b211a3e88..5d383fffe083 100644
> --- a/drivers/iio/imu/bmi323/bmi323_core.c
> +++ b/drivers/iio/imu/bmi323/bmi323_core.c
> @@ -118,6 +118,84 @@ static const struct bmi323_hw bmi323_hw[2] = {
>  	},
>  };
>  
> +struct bmi323_reg_runtime_pm {
> +	unsigned int reg;
> +};
> +
> +static const struct bmi323_reg_runtime_pm bmi323_reg_savestate[] = {
Not useful to have a structure. Just use an array of unsigned int
or maybe even size them to match as u8

static const u8 bmi_regs_tosave[] = {
	BMI323_INT_MAP1_REG,
	...
};
> +	{
> +		.reg = 
> +	},
> +	{
> +		.reg = BMI323_INT_MAP2_REG
> +	},
> +	{
> +		.reg = BMI323_IO_INT_CTR_REG
> +	},
> +	{
> +		.reg = BMI323_IO_INT_CONF_REG
> +	},
> +	{
> +		.reg = BMI323_ACC_CONF_REG
> +	},
> +	{
> +		.reg = BMI323_GYRO_CONF_REG
> +	},
> +	{
> +		.reg = BMI323_FEAT_IO0_REG
> +	},
> +	{
> +		.reg = BMI323_FIFO_WTRMRK_REG
> +	},
> +	{
> +		.reg = BMI323_FIFO_CONF_REG
> +	}
> +};
> +
> +static const struct bmi323_reg_runtime_pm bmi323_ext_reg_savestate[] = {
Similar, just use a u8 array.

> +	{
> +		.reg = BMI323_GEN_SET1_REG
> +	},
> +	{
> +		.reg = BMI323_TAP1_REG
> +	},
> +	{
> +		.reg = BMI323_TAP2_REG
> +	},
> +	{
> +		.reg = BMI323_TAP3_REG
> +	},
> +	{
> +		.reg = BMI323_FEAT_IO0_S_TAP_MSK
> +	},
> +	{
> +		.reg = BMI323_STEP_SC1_REG
> +	},
> +	{
> +		.reg = BMI323_ANYMO1_REG
> +	},
> +	{
> +		.reg = BMI323_NOMO1_REG
> +	},
> +	{
> +		.reg = BMI323_ANYMO1_REG + BMI323_MO2_OFFSET
> +	},
> +	{
> +		.reg = BMI323_NOMO1_REG + BMI323_MO2_OFFSET
> +	},
> +	{
> +		.reg = BMI323_ANYMO1_REG + BMI323_MO3_OFFSET
> +	},
> +	{
> +		.reg = BMI323_NOMO1_REG + BMI323_MO3_OFFSET
> +	}
> +};

>  EXPORT_SYMBOL_NS_GPL(bmi323_core_probe, IIO_BMI323);
>  
> @@ -2125,13 +2222,137 @@ EXPORT_SYMBOL_NS_GPL(bmi323_core_probe, IIO_BMI323);
>  static int bmi323_core_runtime_suspend(struct device *dev)
>  {
>  	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +	struct bmi323_data *data = iio_priv(indio_dev);
> +	struct bmi323_regs_runtime_pm *savestate = &data->runtime_pm_status;
> +
> +	int ret;
>  
> -	return iio_device_suspend_triggering(indio_dev);
> +	guard(mutex)(&data->mutex);
> +
> +	ret = iio_device_suspend_triggering(indio_dev);
> +	if (ret)
> +		return ret;
> +
> +	/*
> +	 * Save registers meant to be restored by resume pm callback.
Single line comment syntax fine here.

> +	 */
> +	for (unsigned int i = 0; i < ARRAY_SIZE(bmi323_reg_savestate); i++) {
> +		const unsigned int reg_addr = bmi323_reg_savestate[i].reg;
Once this is array of u8 I'd just use it in the two places and not bother with
local variable.
> +		unsigned int *reg_val = &savestate->reg_settings[i];

I'd just use &savestate->reg_settings[i] inline and skip the local variable.

> +
> +		ret = regmap_read(data->regmap, reg_addr, reg_val);
> +		if (ret) {
> +			dev_err(data->dev, "Error reading bmi323 reg 0x%x: %d\n",
> +				  reg_addr, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/*
> +	 * Save external registers meant to be restored by resume pm callback.
> +	 */
As above, single line comment fine, if anything.  Fairly obvious what is going on.

> +	for (unsigned int i = 0; i < ARRAY_SIZE(bmi323_ext_reg_savestate); i++) {
> +		const unsigned int ext_reg_addr = bmi323_reg_savestate[i].reg;
> +		unsigned int *ext_reg_val = &savestate->reg_settings[i];
Likewise, local variable doesn't add thing much.
> +
> +		ret = bmi323_read_ext_reg(data, ext_reg_addr, ext_reg_val);
> +		if (ret) {
> +			dev_err(data->dev, "Error reading bmi323 external reg 0x%x: %d\n",
> +				  ext_reg_addr, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/*
> +	 * Perform soft reset to place the device in its lowest power state.
> +	 */
> +	ret = regmap_write(data->regmap, BMI323_CMD_REG, BMI323_RST_VAL);
> +	if (ret)
> +		return ret;
> +
> +	return 0;
>  }
>  
>  static int bmi323_core_runtime_resume(struct device *dev)
>  {
>  	struct iio_dev *indio_dev = dev_get_drvdata(dev);
> +	struct bmi323_data *data = iio_priv(indio_dev);
> +	struct bmi323_regs_runtime_pm *savestate = &data->runtime_pm_status;
> +
No blank line here. Doesn't add any value.

> +	int ret;
> +
> +	guard(mutex)(&data->mutex);
> +
> +	/*
> +	 * Perform the device power-on and initial setup once again
> +	 * after being reset in the lower power state by runtime-pm.
> +	 */
> +	ret = bmi323_init(data);
> +	if (!ret)
> +		return ret;
> +
> +	/* Register must be cleared before changing an active config */
> +	ret = regmap_write(data->regmap, BMI323_FEAT_IO0_REG, 0);
> +	if (ret) {
> +		dev_err(data->dev, "Error stopping feature engine\n");
> +		return ret;
> +	}
> +
> +	/*
> +	 * Restore external registers saved by suspend pm callback.
Single line comment
> +	 */
> +	for (unsigned int i = 0; i < ARRAY_SIZE(bmi323_ext_reg_savestate); i++) {
> +		const unsigned int ext_reg_addr = bmi323_reg_savestate[i].reg;
> +		const unsigned int ext_reg_val = savestate->reg_settings[i];
comments above apply here as well.

> +
> +		ret = bmi323_write_ext_reg(data, ext_reg_addr, ext_reg_val);
> +		if (ret) {
> +			dev_err(data->dev, "Error writing bmi323 external reg 0x%x: %d\n",
> +				  ext_reg_addr, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/*
> +	 * Restore registers saved by suspend pm callback.
> +	 */
> +	for (unsigned int i = 0; i < ARRAY_SIZE(bmi323_reg_savestate); i++) {
> +		const unsigned int reg_addr = bmi323_reg_savestate[i].reg;
> +		const unsigned int reg_val = savestate->reg_settings[i];
> +
> +		ret = regmap_write(data->regmap, reg_addr, reg_val);
> +		if (ret) {
> +			dev_err(data->dev, "Error writing bmi323 reg 0x%x: %d\n",
> +				  reg_addr, ret);
> +			return ret;
> +		}
> +	}
> +
> +	/*
> +	 * Clear old FIFO samples that might be generated before suspend
> +	 * or generated from a peripheral state not equal to the saved one.
> +	 */
> +	if (data->state == BMI323_BUFFER_FIFO) {
> +		ret = regmap_write(data->regmap, BMI323_FIFO_CTRL_REG,
> +			   BMI323_FIFO_FLUSH_MSK);
> +		if (ret) {
> +			dev_err(data->dev, "Error flushing FIFO buffer: %d\n", ret);
> +			return ret;
> +		}
> +	}
> +
> +	unsigned int val;

Variable declarations still in old school c style, so at the top of the scope.

> +
> +	ret = regmap_read(data->regmap, BMI323_ERR_REG, &val);
> +	if (ret) {
> +		dev_err(data->dev, "Error reading bmi323 error register: %d\n", ret);
> +		return ret;
> +	}
> +
> +	if (val) {
> +		dev_err(data->dev, "Sensor power error in PM = 0x%x\n", val);
> +		return -EINVAL;
> +	}
>  
>  	return iio_device_resume_triggering(indio_dev);
>  }