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SubjectRe: [PATCH] ds2782_battery: add support for ds2786 battery gas gauge
Hi Ryan,

Ryan Mallon wrote:
> Mike Rapoport wrote:
>> From: Yulia Vilensky <vilensky@compulab.co.il>
>
> Thanks for this, some comments below.
>
>> Signed-off-by: Yulia Vilensky <vilensky@compulab.co.il>
>> Signed-off-by: Mike Rapoport <mike@compulab.co.il>
>> ---
>> drivers/power/Kconfig | 4 +-
>> drivers/power/ds2782_battery.c | 217 +++++++++++++++++++++++++++++++--------
>> include/linux/ds2782_battery.h | 8 ++
>> 3 files changed, 182 insertions(+), 47 deletions(-)
>> create mode 100644 include/linux/ds2782_battery.h
>>
>> diff --git a/drivers/power/Kconfig b/drivers/power/Kconfig
>> index faaa9b4..d8b8a19 100644
>> --- a/drivers/power/Kconfig
>> +++ b/drivers/power/Kconfig
>> @@ -65,10 +65,10 @@ config BATTERY_DS2760
>> Say Y here to enable support for batteries with ds2760 chip.
>>
>> config BATTERY_DS2782
>> - tristate "DS2782 standalone gas-gauge"
>> + tristate "DS2782/DS2786 standalone gas-gauge"
>> depends on I2C
>> help
>> - Say Y here to enable support for the DS2782 standalone battery
>> + Say Y here to enable support for the DS2782/DS2786 standalone battery
>
> I have only used the DS2782 chip. Can we just change this to DS278x? May
> as well change to CONFIG_BATTERY_DS278x while we are here.
>

Shall we move ds2782_battery.c to ds278x_battery.c at the same time?
Changing Kconfig invites the .c file move as well :)

>> gas-gauge.
>>
>> config BATTERY_PMU
>> diff --git a/drivers/power/ds2782_battery.c b/drivers/power/ds2782_battery.c
>> index 99c8997..0df49b4 100644
>> --- a/drivers/power/ds2782_battery.c
>> +++ b/drivers/power/ds2782_battery.c
>> @@ -5,6 +5,8 @@
>> *
>> * Author: Ryan Mallon <ryan@bluewatersys.com>
>> *
>> + * DS278 added by Yulia Vilensky <vilensky@compulab.co.il>
>> + *
>> * This program is free software; you can redistribute it and/or modify
>> * it under the terms of the GNU General Public License version 2 as
>> * published by the Free Software Foundation.
>> @@ -20,6 +22,7 @@
>> #include <linux/idr.h>
>> #include <linux/power_supply.h>
>> #include <linux/slab.h>
>> +#include <linux/ds2782_battery.h>
>>
>> #define DS2782_REG_RARC 0x06 /* Remaining active relative capacity */
>>
>> @@ -33,18 +36,39 @@
>> /* Current unit measurement in uA for a 1 milli-ohm sense resistor */
>> #define DS2782_CURRENT_UNITS 1563
>>
>> -#define to_ds2782_info(x) container_of(x, struct ds2782_info, battery)
>> +#define DS2786_REG_RARC 0x02 /* Remaining active relative capacity */
>> +
>> +#define DS2786_REG_VOLT_MSB 0x0c
>> +#define DS2786_REG_TEMP_MSB 0x0a
>> +#define DS2786_REG_CURRENT_MSB 0x0e
>
> #define DS278x_REG_CURRENT_MSB 0x0e
>
> Its the same register on both chips, no need for two #defines. Same of
> the other registers, except for RARC.

Ok.

>> +
>> +#define DS2786_CURRENT_UNITS 25
>
> If we make this a member of the info structure, we can easily use it in
> calculations for both chips, ie
>
> current_uA = raw * (info->current_units / sense_res);

not quite, see comments below.

>> +#define DS278X_SIGN_BIT_MASK16 0x8000
>> +
>> +struct ds278x_info;
>>
>> -struct ds2782_info {
>> +struct ds278x_battery_ops {
>> + int (*get_temp)(struct ds278x_info *info, int *temp);
>> + int (*get_current)(struct ds278x_info *info, int *current_uA);
>> + int (*get_voltage)(struct ds278x_info *info, int *voltage_uA);
>> + int (*get_capacity)(struct ds278x_info *info, int *capacity_uA);
>> +};
>> +

[ snip ]

>>
>> -static int ds2782_get_status(struct ds2782_info *info, int *status)
>> +static int ds2786_get_temp(struct ds278x_info *info, int *temp)
>> +{
>> + s16 raw;
>> + int err;
>> +
>> + /*
>> + * Temperature is measured in units of 0.125 degrees celcius, the
>> + * power_supply class measures temperature in tenths of degrees
>> + * celsius. The temperature value is stored as a 10 bit number, plus
>> + * sign in the upper bits of a 16 bit register.
>> + */
>> + err = ds278x_read_reg16(info, DS2786_REG_TEMP_MSB, &raw);
>> + if (err)
>> + return err;
>> +
>> + if (raw & DS278X_SIGN_BIT_MASK16)
>> + *temp = -(((~raw >> 5)+1) * 125)/100;
>> + else
>> + *temp = ((raw >> 5) * 125)/100;
>> +
>> + return 0;
>> +}
>
> This is basically the same as the ds2782 version. See Jean's comments on
> my original patch about the sign math:
> http://www.mail-archive.com/linux-i2c@vger.kernel.org/msg01220.html

Ok, we'll fix the math

>> +static int ds2786_get_current(struct ds278x_info *info, int *current_uA)
>> +{
>> + int err;
>> + s16 raw;
>> +
>> + err = ds278x_read_reg16(info, DS2786_REG_CURRENT_MSB, &raw);
>> + if (err)
>> + return err;
>> +
>> + if (raw & DS278X_SIGN_BIT_MASK16)
>> + *current_uA = -(((~raw >> 4)+1) *
>> + (DS2786_CURRENT_UNITS / info->rsns));
>> + else
>> + *current_uA = (raw >> 4) *
>> + (DS2786_CURRENT_UNITS / info->rsns);
>> + return 0;
>
> Can we combine the implementations of the get_current function? Both
> have get rsns (though in different ways) and eventually divide the
> current register by the rsns value? Possibly move the get_rsns into
> separate battery ops and attempt to coalesce these?

It's possible to have get_rsns and coalesce _get_current for both chips.
However, ds2872 and ds2786 need slightly different formula for current
calculations. Part of these calculations can be wrapped into
ds2786_get_rsns, but it makes the later really not clear to follow.

>> +}
>> +
>> +static int ds2786_get_voltage(struct ds278x_info *info, int *voltage_uA)
>> +{
>> + s16 raw;
>> + int err;
>> +
>> + /*
>> + * Voltage is measured in units of 1.22mV. The voltage is stored as
>> + * a 10-bit number plus sign, in the upper bits of a 16-bit register
>> + */
>> + err = ds278x_read_reg16(info, DS2786_REG_VOLT_MSB, &raw);
>> + if (err)
>> + return err;
>> +
>> + if (raw & DS278X_SIGN_BIT_MASK16)
>> + *voltage_uA = -(((~raw >> 3)+1) * 1220);
>> + else
>> + *voltage_uA = (raw >> 3) * 1220;
>> + return 0;
>> +}
>
> Again, if we move the multiplier value (1220 for ds2786 and 4800 for
> ds2782) to the info structure then we can use the same code to get the
> voltage for both chips.

We need to the divider to the info structure as well.

>> +static int ds2786_get_capacity(struct ds278x_info *info, int *capacity)
>> +{
>> + int err;
>> + u8 raw;
>> +
>> + err = ds278x_read_reg(info, DS2786_REG_RARC, &raw);
>> + if (err)
>> + return err;
>> + /* Relative capacity is displayed with resolution 0.5 % */
>> + *capacity = raw/2 ;
>> + return 0;
>> +}
>
> Same here, move the divider to the info structure (will be 1 for ds2782)
> and combine the functions.

Here again we need to add the divider and RARC register to the info
structure.

>> +
>> +static int ds278x_get_status(struct ds278x_info *info, int *status)
>> {

[ snip ]

>>
>> -static int ds2782_battery_probe(struct i2c_client *client,
>> +static struct ds278x_battery_ops ds278x_ops[] = {
>> + [0] = {
>> + .get_temp = ds2782_get_temp,
>> + .get_current = ds2782_get_current,
>> + .get_voltage = ds2782_get_voltage,
>> + .get_capacity = ds2782_get_capacity,
>> + },
>> + [1] = {
>> + .get_temp = ds2786_get_temp,
>> + .get_current = ds2786_get_current,
>> + .get_voltage = ds2786_get_voltage,
>> + .get_capacity = ds2786_get_capacity,
>> + }
>> +};
>> +
>> +static int ds278x_battery_probe(struct i2c_client *client,
>> const struct i2c_device_id *id)
>> {
>> - struct ds2782_info *info;
>> + struct ds278x_platform_data *pdata = client->dev.platform_data;
>> + struct ds278x_info *info;
>> int ret;
>> int num;
>>
>> + /*
>> + * ds2786 should have the sense resistor value set
>> + * in the platform data .
>> + */
>> + if (id->driver_data == 1 && pdata == 0) {
>> + dev_err(&client->dev, "missing platform data for ds2786\n");
>> + return -EINVAL;
>> + }
>> +
>> /* Get an ID for this battery */
>> ret = idr_pre_get(&battery_id, GFP_KERNEL);
>> if (ret == 0) {
>> @@ -269,7 +392,7 @@ static int ds2782_battery_probe(struct i2c_client *client,
>> goto fail_info;
>> }
>>
>> - info->battery.name = kasprintf(GFP_KERNEL, "ds2782-%d", num);
>> + info->battery.name = kasprintf(GFP_KERNEL, "%s-%d", client->name, num);
>> if (!info->battery.name) {
>> ret = -ENOMEM;
>> goto fail_name;
>> @@ -277,7 +400,10 @@ static int ds2782_battery_probe(struct i2c_client *client,
>>
>> i2c_set_clientdata(client, info);
>> info->client = client;
>> - ds2782_power_supply_init(&info->battery);
>> + info->id = num;
>> + info->ops = &ds278x_ops[id->driver_data];

Summarizing all the parameters that should be added to the info
structure we'd get here switch with lots of 'param = value' for each
case which seems to me less elegant and efficient than simple info->ops
assignment. I think keeping different functions for ds2782 and ds2786
keeps the code more readable and easier to follow.

>> + info->rsns = pdata->rsns;
>> + ds278x_power_supply_init(&info->battery);
>>
>> ret = power_supply_register(&client->dev, &info->battery);
>> if (ret) {
>> @@ -300,31 +426,32 @@ fail_id:
>> return ret;
>> }
>>
>> -static const struct i2c_device_id ds2782_id[] = {
>> +static const struct i2c_device_id ds278x_id[] = {
>> {"ds2782", 0},
>> + {"ds2786", 1},
>> {},
>> };
>>
>> -static struct i2c_driver ds2782_battery_driver = {
>> +static struct i2c_driver ds278x_battery_driver = {
>> .driver = {
>> .name = "ds2782-battery",
>> },
>> - .probe = ds2782_battery_probe,
>> - .remove = ds2782_battery_remove,
>> - .id_table = ds2782_id,
>> + .probe = ds278x_battery_probe,
>> + .remove = ds278x_battery_remove,
>> + .id_table = ds278x_id,
>> };
>>
>> -static int __init ds2782_init(void)
>> +static int __init ds278x_init(void)
>> {
>> - return i2c_add_driver(&ds2782_battery_driver);
>> + return i2c_add_driver(&ds278x_battery_driver);
>> }
>> -module_init(ds2782_init);
>> +module_init(ds278x_init);
>>
>> -static void __exit ds2782_exit(void)
>> +static void __exit ds278x_exit(void)
>> {
>> - i2c_del_driver(&ds2782_battery_driver);
>> + i2c_del_driver(&ds278x_battery_driver);
>> }
>> -module_exit(ds2782_exit);
>> +module_exit(ds278x_exit);
>>
>> MODULE_AUTHOR("Ryan Mallon <ryan@bluewatersys.com>");
>> MODULE_DESCRIPTION("Maxim/Dallas DS2782 Stand-Alone Fuel Gauage IC driver");
>> diff --git a/include/linux/ds2782_battery.h b/include/linux/ds2782_battery.h
>> new file mode 100644
>> index 0000000..b4e281f
>> --- /dev/null
>> +++ b/include/linux/ds2782_battery.h
>> @@ -0,0 +1,8 @@
>> +#ifndef __LINUX_DS2782_BATTERY_H
>> +#define __LINUX_DS2782_BATTERY_H
>> +
>> +struct ds278x_platform_data {
>> + int rsns;
>> +};
>> +
>> +#endif
>
>


--
Sincerely yours,
Mike.


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