linux-kernel - Re: [RESEND 1/2] power: supply: add CW2015 Fuel Gauge driver

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Date:   Tue, 14 Jan 2020 08:17:55 +0100
From:   Tobias Schramm <t.schramm@...jaro.org>
To:     Sebastian Reichel <sre@...nel.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Mark Rutland <mark.rutland@....com>, linux-pm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND 1/2] power: supply: add CW2015 Fuel Gauge driver

Hi Sebastian,

thanks for the review!

>> +#ifdef CONFIG_OF
>> +static int cw2015_parse_dt(struct cw_battery *cw_bat)
>> +{
>> +	struct device *dev = &cw_bat->client->dev;
>> +	struct device_node *node = dev->of_node;
>> +	struct property *prop;
>> +	int length;
>> +	u32 value;
>> +	int ret;
>> +	struct cw_bat_platform_data *data = &cw_bat->plat_data;
>> +
>> +	if (!node)
>> +		return -ENODEV;
>> +
>> +	memset(data, 0, sizeof(*data));
>> +
>> +	/* determine the number of config info */
>> +	prop = of_find_property(node, PREFIX"bat-config-info", &length);
>> +	if (!prop)
>> +		return -EINVAL;
>> +
>> +	length /= sizeof(u32);
>> +
>> +	if (length > 0) {
>> +		size_t size = sizeof(*data->cw_bat_config_info) * length;
>> +
>> +		data->cw_bat_config_info = devm_kzalloc(dev, size, GFP_KERNEL);
>> +		if (!data->cw_bat_config_info)
>> +			return -ENOMEM;
>> +
>> +		ret = of_property_read_u32_array(node, PREFIX"bat-config-info",
>> +						 data->cw_bat_config_info,
>> +						 length);
>> +		if (ret < 0)
>> +			return ret;
>> +	}
> 
> In its current state it does not look like data for DT. What
> information is stored in this "config info"?
>
Truth is: I don't know. The format of this blob is neither disclosed nor 
even mentioned by publicly available datasheets.
As far as I can tell it is information about the battery used, most 
likely data on chemistry and design capacity of the pack.
Since this depends on the cell built into a device I'd expect it to be 
located in the DT.

>> +	cw_bat->bat_mode = MODE_BATTERY;
>> +	cw_bat->monitor_sec = CW2015_DEFAULT_MONITOR_SEC *
>> +			      CW2015_TIMER_MS_COUNTS;
>> +
>> +	prop = of_find_property(node, PREFIX"voltage-divider", &length);
>> +	if (prop) {
>> +		length /= sizeof(u32);
>> +		if (length != 2) {
>> +			dev_err(dev, "Length of voltage divider array must be "
>> +				"2, not %u\n", length);
>> +			return -EINVAL;
>> +		}
>> +		ret = of_property_read_u32_index(node, PREFIX"voltage-divider",
>> +						 0, &data->divider_high);
>> +		if (ret) {
>> +			dev_err(dev, "Failed to read value of high side "
>> +				"voltage divider resistor: %d\n", ret);
>> +			return ret;
>> +		}
>> +		ret = of_property_read_u32_index(node, PREFIX"voltage-divider",
>> +						 1, &data->divider_low);
>> +		if (ret) {
>> +			dev_err(dev, "Failed to read value of low side "
>> +				"voltage divider resistor: %d\n", ret);
>> +			return ret;
>> +		}
>> +	}
>> +
>> +	ret = of_property_read_u32(node, PREFIX"divider-res2", &value);
>> +	if (ret < 0)
>> +		value = 0;
>> +	data->divider_low = value;
>> +
>> +	ret = of_property_read_u32(node, PREFIX"virtual-power", &value);
>> +	if (ret < 0)
>> +		value = 0;
>> +	cw_bat->bat_mode = value;
> 
> of_property_read_bool
> 
>> +	ret = of_property_read_u32(node, PREFIX"monitor-interval", &value);
>> +	if (ret < 0)
>> +		dev_err(dev, "monitor-interval missing!\n");
>> +	else
>> +		cw_bat->monitor_sec = value * CW2015_TIMER_MS_COUNTS;
>> +
>> +	ret = of_property_read_u32(node, PREFIX"design-capacity", &value);
>> +	if (ret < 0) {
>> +		dev_err(dev, "design-capacity missing!\n");
>> +		data->design_capacity = 2000;
>> +	} else {
>> +		data->design_capacity = value;
>> +	}
>> +
>> +	of_property_read_u8(node, PREFIX"alert-level", &cw_bat->alert_level);
>> +	if (cw_bat->alert_level > 100) {
>> +		dev_err(dev, "invalid alert_level, clamping to 100 %%\n");
>> +		cw_bat->alert_level = 100;
>> +	}
> 
> This does not belong into DT.
>
Is there any interface that allows setting a hardware battery alert 
level? Or should I just drop it altogether?

Tobias