[PATCHv1 1/3] hwmon: Add support for GMT G762/G763 PWM fan controller

[Arnaud Ebalard]

Hi Andrew,

Andrew Lunn <andrew at lunn.ch> writes:

>> +struct g762_data {
>> +	struct i2c_client *client;
>> +	struct device *hwmon_dev;
>> +
>> +	/* update mutex */
>> +	struct mutex update_lock;
>> +
>> +	/* board specific parameters. */
>> +	u32 clk; /* default 32kHz */
>> +
>> +	/* g762 register cache */
>> +	bool valid;
>> +	unsigned long last_updated; /* in jiffies */
>> +
>> +	u8 set_cnt;  /* RPM cmd in close loop control */
>> +	u8 act_cnt;  /* formula: cnt = (CLK * 30)/(rpm * P) */
>> +	u8 fan_sta;  /* bit 0: set when actual fan speed is more than
>> +		      *        25% outside requested fan speed
>> +		      * bit 1: set when no transition occurs on fan
>> +		      *        pin for 0.7s
>> +		      */
>> +	u8 set_out;  /* output voltage/PWM duty in open loop control */
>> +	u8 fan_cmd1; /*   0: FG_PLS_ID0 FG pulses count per revolution
>> +		      *      0: 2 counts per revolution
>> +		      *      1: 4 counts per revolution
>> +		      *   1: PWM_POLARITY 1: negative_duty
>> +		      *                   0: positive_duty
>> +		      * 2,3: [FG_CLOCK_ID0, FG_CLK_ID1]
>> +		      *         00: Divide fan clock by 1
>> +		      *         01: Divide fan clock by 2
>> +		      *         10: Divide fan clock by 4
>> +		      *         11: Divide fan clock by 8
>> +		      *   4: FAN_MODE 1:close-loop, 0:open-loop
>> +		      *   5: OUT_MODE 1:PWM, 0:DAC
>> +		      *   6: DET_FAN_OOC enable "fan ooc" status
>> +		      *   7: DET_FAN_FAIL enable "fan fail" status
>> +		      */
>> +	u8 fan_cmd2; /* 0,1: FAN_STARTV 0,1,2,3 -> 0,32,64,96 dac_code
>> +		      * 2,3: FG_GEAR_MODE
>> +		      *         00: div = 1
>> +		      *         01: div = 2
>> +		      *         10: div = 4
>> +		      *   4: Mask ALERT# (g763 only)
>> +		      */
>
> You could consider using regmap for holding this cache.
>
> http://elceurope2012.sched.org/event/100619b669ce5767341624253aa03659?iframe=no&w=900&sidebar=yes&bg=no#.UXdspHLQ5jM
>
> http://elinux.org/ELCE_Europe_2012_Presentations

Interesting. As I am not yet familiar w/ regmap I would prefer having
the driver accepted during merge window with current data structure and
then convert it to regmap. But I will take a look (e.g. will study
fca1dd03 for instance). Thanks for the pointers. 

>> +/*
>> + * Helpers to import hardware characteristics from .dts file and overload
>> + * default config values.
>> + */
>> +
>> +#ifdef CONFIG_OF
>
> Can the driver be used without device tree? Would it be simpler to
>  just add depends OF in the Kconfig entry?

It can be used if the default params (or those configured by u-boot I
guess) fit your needs. I think it would be fairly easy to extend the
driver later to expose g762_config struct to allow parameters to be set
w/o using OF. If someone wants to do that, I think it is better to not
depend on OF in Kconfig at the moment but I have not strong argument
other that that one. I'll let you decide.

Cheers,

a+