RE: [PATCH] regulator: MAX8998: set_voltage bugfix. ramp_up delay and min/max voltage

[Marek Szyprowski <m.szyprowski@samsung.com>]

Hello,

On Friday, July 16, 2010 10:09 AM MyungJoo Ham wrote:

> Two issues are addressed for max8998_set_voltage function.
> 
> 1. Min/Max Voltage.
> 
> 	max8998_set_voltage had been using the voltage value of
> 
> 	min ( voltage[i] >= max_vol , i )
> 
> 	This is corrected to use:
> 
> 	min ( voltage[i] >= min_vol , i )
> 
> 2. Ramp Up Delay.
> 
> 	max8998_set_voltage should provide delay for BUCK1/2
> if ENRAMP is on. It reads RAMP value from ONOFF4 register to determine
> RAMP delay length. However, when max8998_set_voltage's new voltage is
> lower than the previous, we don't care because it does not deteriorate
> the stability.
> 
> Signed-off-by: MyungJoo Ham <myungjoo.ham@samsung.com>
> Signed-off-by: Kyungmin Park <kyungmin.park@samsung.com>

Acked-by: Marek Szyprowski <m.szyprowski@samsung.com>

> --
> I've omitted some CC in the previous email, adding them here. Sorry for the
> duplicated submission.
> ---
>  drivers/regulator/max8998.c |   30 ++++++++++++++++++++++++++++--
>  1 files changed, 28 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/regulator/max8998.c b/drivers/regulator/max8998.c
> index 1cca8b5..99c5279 100644
> --- a/drivers/regulator/max8998.c
> +++ b/drivers/regulator/max8998.c
> @@ -28,6 +28,7 @@
>  #include <linux/slab.h>
>  #include <linux/interrupt.h>
>  #include <linux/mutex.h>
> +#include <linux/delay.h>
>  #include <linux/platform_device.h>
>  #include <linux/regulator/driver.h>
>  #include <linux/mfd/max8998.h>
> @@ -302,10 +303,13 @@ static int max8998_set_voltage(struct regulator_dev
> *rdev,
>  	struct max8998_data *max8998 = rdev_get_drvdata(rdev);
>  	struct i2c_client *i2c = max8998->iodev->i2c;
>  	int min_vol = min_uV / 1000, max_vol = max_uV / 1000;
> +	int previous_vol = 0;
>  	const struct voltage_map_desc *desc;
>  	int ldo = max8998_get_ldo(rdev);
>  	int reg, shift = 0, mask, ret;
>  	int i = 0;
> +	u8 val;
> +	bool en_ramp = false;
> 
>  	if (ldo > ARRAY_SIZE(ldo_voltage_map))
>  		return -EINVAL;
> @@ -317,15 +321,37 @@ static int max8998_set_voltage(struct regulator_dev
> *rdev,
>  	if (max_vol < desc->min || min_vol > desc->max)
>  		return -EINVAL;
> 
> -	while (desc->min + desc->step*i < max_vol &&
> +	while (desc->min + desc->step*i < min_vol &&
>  	       desc->min + desc->step*i < desc->max)
>  		i++;
> 
> +	if (desc->min + desc->step*i > max_vol)
> +		return -EINVAL;
> +
>  	ret = max8998_get_voltage_register(rdev, &reg, &shift, &mask);
>  	if (ret)
>  		return ret;
> 
> -	return max8998_update_reg(i2c, reg, i<<shift, mask<<shift);
> +	/* wait for RAMP_UP_DELAY if rdev is BUCK1/2 and
> +	 * ENRAMP is ON */
> +	if (ldo == MAX8998_BUCK1 || ldo == MAX8998_BUCK2) {
> +		max8998_read_reg(i2c, MAX8998_REG_ONOFF4, &val);
> +		if (val & (1 << 4)) {
> +			en_ramp = true;
> +			previous_vol = max8998_get_voltage(rdev);
> +		}
> +	}
> +
> +	ret = max8998_update_reg(i2c, reg, i<<shift, mask<<shift);
> +
> +	if (en_ramp == true) {
> +		int difference = desc->min + desc->step * i
> +			- previous_vol / 1000;
> +		if (difference > 0)
> +			udelay(difference / ((val & 0x0f) + 1));
> +	}
> +
> +	return ret;
>  }
> 
>  static struct regulator_ops max8998_ldo_ops = {
> --
> 1.6.3.3


Best regards
--
Marek Szyprowski
Samsung Poland R&D Center