Re: [PATCH 14/15] power: supply: Add driver for Cherry Trail Whiskey Cove PMIC Fuel Gauge

Andy Shevchenko
2017-03-17T17:58:49Z

On Fri, 2017-03-17 at 10:55 +0100, Hans de Goede wrote:
> Add a driver for the Cherry Trail Whiskey Cove PMIC Fuel Gauge, note
> the Cherry Trail Whiskey Cove PMIC Fuel Gauge block is purely a fuel
> gauge
> and not a full battery controller. As such it offers a platform_data
> callback for extra power_supply properties for the actual external-
> charger
> ic driver and does not register a power_supply itself.

ic -> IC

Can we move to something like built-in device properties for additional
properties instead of extending platform data?

> +config CHT_WC_FUEL_GAUGE

I would use similar pattern:

FUEL_GAUGE_INTEL_CHTWC (or FUEL_GAUGE_CHTWC, but this might be less
obvious about vendor)

> --- /dev/null
> +++ b/drivers/power/supply/cht_wc_fuel_gauge.c
> @@ -0,0 +1,209 @@
> +/*
> + * Intel CHT Whiskey Cove Fuel Gauge driver

CHT -> Cherry Trail

> + *
> + * Cherrytrail Whiskey Cove devices have 2 functional blocks which
> interact
> + * with the battery.

Cherry Trail?

> +#define REG_CHARGE_NOW 0x05
> +#define REG_VOLTAGE_NOW 0x09
> +#define REG_CURRENT_NOW 0x0a
> +#define REG_CURRENT_AVG 0x0b
> +#define REG_CHARGE_FULL 0x10
> +#define REG_CHARGE_DESIGN 0x18
> +#define REG_VOLTAGE_AVG 0x19

> +#define REG_VOLTAGE_OCV 0x1b /* Only updated during
> charging */

I think comment makes more sense where actual update is happening in the
code.

> +
> +static int cht_wc_fg_read(struct cht_wc_fg_data *fg, u8 reg,
> +   union power_supply_propval *val, int scale,
> +   int sign_extend)
> +{
> + int ret;
> +
> + ret = i2c_smbus_read_word_data(fg->client, reg);
> + if (ret < 0)
> + return ret;
> +
> + if (sign_extend)
> + ret = sign_extend32(ret, 15);

Magic?

> +
> + val->intval = ret * scale;
> +
> + return 0;
> +}

> +
> +int cht_wc_fg_get_property(enum power_supply_property prop,
> +    union power_supply_propval *val)
> +{
> + int ret = 0;

Sounds like redundant assignment...

> +
> + mutex_lock(&cht_wc_fg_mutex);
> +
>

> + if (!cht_wc_fg) {
> + ret = -ENXIO;
> + goto out_unlock;
> + }

...otherwise maybe

ret = cht_wc_fg ? 0 : -ENXIO;
if (ret)
goto ...;

?

> + default:
> + ret = -ENODATA;
> + }
> +out_unlock:
> + mutex_unlock(&cht_wc_fg_mutex);
> + return ret;
> +}
> +EXPORT_SYMBOL_GPL(cht_wc_fg_get_property);

> +
> +static int cht_wc_fg_probe(struct i2c_client *client,
> + const struct i2c_device_id *i2c_id)
> +{
> + struct device *dev = &client->dev;
> + struct cht_wc_fg_data *fg;
> + acpi_status status;
> + unsigned long long ptyp;

> + status = acpi_evaluate_integer(ACPI_HANDLE(dev), "PTYP",
> NULL, &ptyp);
> + if (ACPI_FAILURE(status)) {
> + dev_err(dev, "Failed to get PTYPE\n");
> + return -ENODEV;
> + }
> +
> + /*
> +  * The same ACPI HID is used with different PMICs check PTYP
> to
> +  * ensure that we are dealing with a Whiskey Cove PMIC.
> +  */
> + if (ptyp != CHT_WC_FG_PTYPE)
> + return -ENODEV;

Logically I would split this part to be a main driver for device which
would use actual driver based on this, though I think it too much churn
for no benefit right now.

> + mutex_lock(&cht_wc_fg_mutex);
> + cht_wc_fg = fg;
> + mutex_unlock(&cht_wc_fg_mutex);

It's pity we have no common storage of single possible present device
drivers in the kernel. I would use some kind of framework rather then
keeping all those global variables with locking. Perhaps radix / RB
tree.

> +
> + return 0;
> +}

--
Andy Shevchenko <andriy.shevchenko@linux.intel.com>
Intel Finland Oy