[PATCH 2/5] power: supply: cw2015: Add support for dual-cell configurations

[Sebastian Reichel]

Hi,

On Fri, Jul 26, 2024 at 02:49:45PM GMT, Chris Morgan wrote:
> From: Chris Morgan <macromorgan at hotmail.com>
> 
> The Cellwise cw2015 datasheet reports that it can handle two cells
> in a series configuration. Allow a device tree parameter to note
> this condition so that the driver reports the correct voltage values
> to userspace.

I found this:

http://www.cellwise-semi.com/Public/assests/menu/20230302/6400076806706.pdf

Which says:

  CW2015 can be used in 2 or more batteries connected in series, or
  several cells connected in parallel.

So dual-cell seems like a bad property name. Instead the number of
serial cells should be provided. This property is then not really
specific to the Cellwise fuel gauge and instead a property of the
battery pack (i.e. simple-battery.yaml).

> Signed-off-by: Chris Morgan <macromorgan at hotmail.com>
> ---
>  drivers/power/supply/cw2015_battery.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/power/supply/cw2015_battery.c b/drivers/power/supply/cw2015_battery.c
> index f63c3c410451..b23a6d4fa4fa 100644
> --- a/drivers/power/supply/cw2015_battery.c
> +++ b/drivers/power/supply/cw2015_battery.c
> @@ -77,6 +77,8 @@ struct cw_battery {
>  	u32 poll_interval_ms;
>  	u8 alert_level;
>  
> +	bool dual_cell;
> +
>  	unsigned int read_errors;
>  	unsigned int charge_stuck_cnt;
>  };
> @@ -325,6 +327,9 @@ static int cw_get_voltage(struct cw_battery *cw_bat)
>  	 */
>  	voltage_mv = avg * 312 / 1024;
>  
> +	if (cw_bat->dual_cell)
> +		voltage_mv *= 2;

Unfortunately there are no details in the document, but this looks
very fishy. Does it only measure the first cell and hope that the
other cells have the same voltage?

This (unmerged) series also applies to your problem to some degree:

https://lore.kernel.org/all/20240416121818.543896-3-mike.looijmans@topic.nl/

-- Sebastian

>  	dev_dbg(cw_bat->dev, "Read voltage: %d mV, raw=0x%04x\n",
>  		voltage_mv, reg_val);
>  	return voltage_mv;
> @@ -587,6 +592,8 @@ static int cw2015_parse_properties(struct cw_battery *cw_bat)
>  			return ret;
>  	}
>  
> +	cw_bat->dual_cell = device_property_read_bool(dev, "cellwise,dual-cell");
> +
>  	ret = device_property_read_u32(dev, "cellwise,monitor-interval-ms",
>  				       &cw_bat->poll_interval_ms);
>  	if (ret) {
> -- 
> 2.34.1
> 
> 
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