[v4,13/15] power: axp20x_battery: Add constant charge current table

Add a table-based lookup method for constant charge current,
which is necessary when the setting cannot be represented as
a linear range.

This also replaces the hard-coded 300 mA default ccc setting
if the DT-specified value is unsupported; the minimum value
for the device is now set exactly instead of relying on the
value being rounded down to a supported value.

Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
---
 drivers/power/supply/axp20x_battery.c | 59 +++++++++++++++++++++------
 1 file changed, 47 insertions(+), 12 deletions(-)

On Wed, Jun 29, 2022 at 4:30 PM Aidan MacDonald
<aidanmacdonald.0x0@gmail.com> wrote:
>
> Add a table-based lookup method for constant charge current,
> which is necessary when the setting cannot be represented as
> a linear range.
>
> This also replaces the hard-coded 300 mA default ccc setting
> if the DT-specified value is unsupported; the minimum value
> for the device is now set exactly instead of relying on the
> value being rounded down to a supported value.

Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

> Signed-off-by: Aidan MacDonald <aidanmacdonald.0x0@gmail.com>
> ---
>  drivers/power/supply/axp20x_battery.c | 59 +++++++++++++++++++++------
>  1 file changed, 47 insertions(+), 12 deletions(-)
>
> diff --git a/drivers/power/supply/axp20x_battery.c b/drivers/power/supply/axp20x_battery.c
> index 9106077c0dbb..401779d84d2b 100644
> --- a/drivers/power/supply/axp20x_battery.c
> +++ b/drivers/power/supply/axp20x_battery.c
> @@ -61,6 +61,14 @@ struct axp20x_batt_ps;
>  struct axp_data {
>         int     ccc_scale;
>         int     ccc_offset;
> +       /*
> +        * Lookup table for constant charge current, if provided this is used
> +        * instead of ccc_scale/ccc_offset.
> +        *
> +        * The table is indexed by the field AXP20X_CHRG_CTRL1_TGT_CURR so it
> +        * must have AXP20X_CHRG_CTRL1_TGT_CURR+1 elements.
> +        */
> +       const int *ccc_table;
>         bool    has_fg_valid;
>         int     (*get_max_voltage)(struct axp20x_batt_ps *batt, int *val);
>         int     (*set_max_voltage)(struct axp20x_batt_ps *batt, int val);
> @@ -176,7 +184,10 @@ static int axp20x_get_constant_charge_current(struct axp20x_batt_ps *axp,
>
>         *val &= AXP20X_CHRG_CTRL1_TGT_CURR;
>
> -       *val = *val * axp->data->ccc_scale + axp->data->ccc_offset;
> +       if (axp->data->ccc_table)
> +               *val = axp->data->ccc_table[*val];
> +       else
> +               *val = *val * axp->data->ccc_scale + axp->data->ccc_offset;
>
>         return 0;
>  }
> @@ -389,16 +400,35 @@ static int axp20x_battery_set_max_voltage(struct axp20x_batt_ps *axp20x_batt,
>                                   AXP20X_CHRG_CTRL1_TGT_VOLT, val);
>  }
>
> +static int axp20x_get_constant_charge_current_sel(struct axp20x_batt_ps *axp_batt,
> +                                                 int charge_current)
> +{
> +       int i;
> +
> +       if (axp_batt->data->ccc_table) {
> +               for (i = AXP20X_CHRG_CTRL1_TGT_CURR; i >= 0; i--) {
> +                       if (axp_batt->data->ccc_table[i] <= charge_current)
> +                               return i;
> +               }
> +
> +               return -EINVAL;
> +       }
> +
> +       i = (charge_current - axp_batt->data->ccc_offset) / axp_batt->data->ccc_scale;
> +       if (i > AXP20X_CHRG_CTRL1_TGT_CURR || i < 0)
> +               return -EINVAL;
> +
> +       return i;
> +}
> +
>  static int axp20x_set_constant_charge_current(struct axp20x_batt_ps *axp_batt,
>                                               int charge_current)
>  {
>         if (charge_current > axp_batt->max_ccc)
>                 return -EINVAL;
>
> -       charge_current = (charge_current - axp_batt->data->ccc_offset) /
> -               axp_batt->data->ccc_scale;
> -
> -       if (charge_current > AXP20X_CHRG_CTRL1_TGT_CURR || charge_current < 0)
> +       charge_current = axp20x_get_constant_charge_current_sel(axp_batt, charge_current);
> +       if (charge_current < 0)
>                 return -EINVAL;
>
>         return regmap_update_bits(axp_batt->regmap, AXP20X_CHRG_CTRL1,
> @@ -410,14 +440,14 @@ static int axp20x_set_max_constant_charge_current(struct axp20x_batt_ps *axp,
>  {
>         bool lower_max = false;
>
> -       charge_current = (charge_current - axp->data->ccc_offset) /
> -               axp->data->ccc_scale;
> -
> -       if (charge_current > AXP20X_CHRG_CTRL1_TGT_CURR || charge_current < 0)
> +       charge_current = axp20x_get_constant_charge_current_sel(axp, charge_current);
> +       if (charge_current < 0)
>                 return -EINVAL;
>
> -       charge_current = charge_current * axp->data->ccc_scale +
> -               axp->data->ccc_offset;
> +       if (axp->data->ccc_table)
> +               charge_current = axp->data->ccc_table[charge_current];
> +       else
> +               charge_current = charge_current * axp->data->ccc_scale + axp->data->ccc_offset;
>
>         if (charge_current > axp->max_ccc)
>                 dev_warn(axp->dev,
> @@ -629,7 +659,12 @@ static int axp20x_power_probe(struct platform_device *pdev)
>                                                                    ccc)) {
>                         dev_err(&pdev->dev,
>                                 "couldn't set constant charge current from DT: fallback to minimum value\n");
> -                       ccc = 300000;
> +
> +                       if (axp20x_batt->data->ccc_table)
> +                               ccc = axp20x_batt->data->ccc_table[0];
> +                       else
> +                               ccc = axp20x_batt->data->ccc_offset;
> +
>                         axp20x_batt->max_ccc = ccc;
>                         axp20x_set_constant_charge_current(axp20x_batt, ccc);
>                 }
> --
> 2.35.1
>