Ira Snyder wrote:
> Add Linux support for the Linear Technology LTC4245 Multiple Supply Hot
> Swap controller I2C monitoring interface.
>
> Signed-off-by: Ira W. Snyder <iws at ovro.caltech.edu>
> ---
>
> I've incorporated the suggestions from my first posting of this driver.
>
> I decided to add current and power readings for the Vee (-12v) voltage,
> as well as the 12v, 5v, and 3v mentioned in the suggestions. This seemed
> reasonable to me.
>
Good.
> I'd appreciate any more suggestions you may have. :)
>
See below :)
<snip>
> +power1_input 12v power usage (mW)
> +power2_input 5v power usage (mW)
> +power3_input 3v power usage (mW)
> +power4_input Vee (-12v) power usage (mW)
> +
These should be in micro Watt so ?W not mW, I know this is not consistentent
with all other input's being in milli something, but the first piece of
supported power measuring hardware we had has sub milliWatt precision, hence
this decision.
<snip>
> +power1_alarm 12v power bad alarm
> +power2_alarm 5v power bad alarm
> +power3_alarm 3v power bad alarm
> +power4_alarm Vee (-12v) power bad alarm
Ah I missed these the first time, looking at the data sheet these are actually
the output voltages going under a specified treshold. So please rename these to
in5_min_alarm to in8_min_alarm
<snip>
> +/* Return the voltage from the given register in millivolts */
> +static u32 ltc4245_get_voltage(struct device *dev, u8 reg)
> +{
> + struct ltc4245_data *data = ltc4245_update_device(dev);
> + const s32 val = data->vregs[reg - 0x10];
> + const u8 regval = val;
> + u32 mv = 0;
> +
> + if (unlikely(val < 0))
> + return 0;
> +
> + switch (reg) {
> + case LTC4245_12VIN:
> + case LTC4245_12VOUT:
> + mv = regval * 55;
> + break;
> + case LTC4245_12VSENSE:
> + mv = regval * 250 / 1000;
You are loosing precision here, regval needs to change 4 steps for mv to change
one. I think it is better todo the current calculation in one step in
get_current() with a comment which contains the multi step floanting point
human readable form. In any case you must change things so that this precision
no longer gets lost.
> + break;
> + case LTC4245_5VIN:
> + case LTC4245_5VOUT:
> + mv = regval * 22;
> + break;
> + case LTC4245_5VSENSE:
> + mv = regval * 125 / 1000;
> + break;
Idem.
> + case LTC4245_3VIN:
> + case LTC4245_3VOUT:
> + mv = regval * 15;
> + break;
> + case LTC4245_3VSENSE:
> + mv = regval * 125 / 1000;
> + break;
Idem.
> + case LTC4245_VEEIN:
> + case LTC4245_VEEOUT:
> + mv = regval * 55;
> + break;
> + case LTC4245_VEESENSE:
> + mv = regval * 250 / 1000;
> + break;
Guess what? Idem :)
> + case LTC4245_GPIOADC1:
> + case LTC4245_GPIOADC2:
> + case LTC4245_GPIOADC3:
> + mv = regval * 10;
> + break;
> + default:
> + WARN_ON_ONCE(1);
> + break;
> + }
> +
> + return mv;
> +}
> +
> +/* Return the current in the given sense register in milliAmperes */
> +static u32 ltc4245_get_current(struct device *dev, u8 reg)
> +{
> + const u32 voltage = ltc4245_get_voltage(dev, reg);
> +
> + switch (reg) {
> + case LTC4245_12VSENSE:
> + return voltage / 50;
This returns the Amperage in Amperes not in milli Amperes. milli Volt divided
by milli Ohm gives Ampere not milli Ampere. So the correct calculation would be:
> + return voltage * 1000 / 50;
At which point the resolution loss described above becomes very relevant!
> + case LTC4245_5VSENSE:
> + /* Fixed point math: mV / 3.5 mOhm == mA */
> + return (voltage * 35 + 5) / 10;
> + case LTC4245_3VSENSE:
> + /* Fixed point math: mV / 2.5 mOhm == mA */
> + return (voltage * 25 + 5) / 10;
> + case LTC4245_VEESENSE:
> + return voltage / 100;
All 3 idem. Also why don't you add + 25 resp. + 50 for correct rounding in the
+/- 12V cases?
> +static ssize_t ltc4245_show_voltage_alarm(struct device *dev,
> + struct device_attribute *da,
> + char *buf)
> +{
> + struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> + struct ltc4245_data *data = ltc4245_update_device(dev);
> + const s32 fault1 = data->cregs[LTC4245_FAULT1];
> + int alarm = 0;
> +
> + if (unlikely(fault1 < 0)) {
> + memset(buf, 0, PAGE_SIZE); /* user should not see old data */
> + return 0;
> + }
> +
> + switch (attr->index) {
> + case LTC4245_12VIN:
> + alarm = fault1 & (1 << 0);
> + break;
> + case LTC4245_5VIN:
> + alarm = fault1 & (1 << 1);
> + break;
> + case LTC4245_3VIN:
> + alarm = fault1 & (1 << 2);
> + break;
> + case LTC4245_VEEIN:
> + alarm = fault1 & (1 << 3);
> + break;
Why don't you just set attr->index to to the mask to test with, or the amount
to shift the 1 and then get rid of this switch case?
> + default:
> + /* If we get here, the developer messed up */
> + WARN_ON_ONCE(1);
> + break;
> + }
> +
> + return snprintf(buf, PAGE_SIZE, "%d\n", alarm ? 1 : 0);
> +}
> +
> +static ssize_t ltc4245_show_current_alarm(struct device *dev,
> + struct device_attribute *da,
> + char *buf)
> +{
> + struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> + struct ltc4245_data *data = ltc4245_update_device(dev);
> + const s32 fault1 = data->cregs[LTC4245_FAULT1];
> + int alarm = 0;
> +
> + if (unlikely(fault1 < 0)) {
> + memset(buf, 0, PAGE_SIZE); /* user should not see old data */
> + return 0;
> + }
> +
> + switch (attr->index) {
> + case LTC4245_12VSENSE:
> + alarm = fault1 & (1 << 4);
> + break;
> + case LTC4245_5VSENSE:
> + alarm = fault1 & (1 << 5);
> + break;
> + case LTC4245_3VSENSE:
> + alarm = fault1 & (1 << 6);
> + break;
> + case LTC4245_VEESENSE:
> + alarm = fault1 & (1 << 7);
> + break;
> + default:
> + /* If we get here, the developer messed up */
> + WARN_ON_ONCE(1);
> + break;
> + }
> +
Idem, note that this function is and most certainly becomes identical to
ltc4245_show_voltage_alarm, so please fold the 2 into 1.
> + return snprintf(buf, PAGE_SIZE, "%d\n", alarm ? 1 : 0);
> +}
> +
> +static ssize_t ltc4245_show_power_alarm(struct device *dev,
> + struct device_attribute *da,
> + char *buf)
> +{
> + struct sensor_device_attribute *attr = to_sensor_dev_attr(da);
> + struct ltc4245_data *data = ltc4245_update_device(dev);
> + const s32 fault2 = data->cregs[LTC4245_FAULT2];
> + int alarm = 0;
> +
> + if (unlikely(fault2 < 0)) {
> + memset(buf, 0, PAGE_SIZE); /* user should not see old data */
> + return 0;
> + }
> +
> + switch (attr->index) {
> + case LTC4245_12VOUT:
> + alarm = fault2 & (1 << 0);
> + break;
> + case LTC4245_5VOUT:
> + alarm = fault2 & (1 << 1);
> + break;
> + case LTC4245_3VOUT:
> + alarm = fault2 & (1 << 2);
> + break;
> + case LTC4245_VEEOUT:
> + alarm = fault2 & (1 << 3);
> + break;
Idem, see below for some more comments about folding all 3 alarm functions into 1.
> + default:
> + /* If we get here, the developer messed up */
> + WARN_ON_ONCE(1);
> + break;
> + }
> +
> + return snprintf(buf, PAGE_SIZE, "%d\n", alarm ? 1 : 0);
> +}
> +
> +/* These macros are used below in constructing device attribute objects
> + * for use with sysfs_create_group() to make a sysfs device file
> + * for each register.
> + */
> +#define LTC4245_VOLTAGE_RO(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_voltage, NULL, ltc4245_cmd_idx)
> +
Please combine this with LTC4245_VOLTAGE_ALARM into one LTC4245_VOLTAGE
define. Just pass in for example in1 as name and use string concatenation to
get the in1_input and in1_min_alarm names, like this: "name ## _input" and
"name ## _min_alarm" .
Also use a third macro argument for the index value for the alarm
SENSOR_DEVICE_ATTR() so that you can directly pass in the shift value / mask
for getting the alarm. Hmm, once you add the in4_min_alarm -> in8_min_alarm,
you need to pass 2 things, which fault register to use and which mask to apply,
better switch to SENSOR_DEVICE_ATTR2 then, which allows you to pass both an
index and a nr.
> +#define LTC4245_CURRENT_RO(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_current, NULL, ltc4245_cmd_idx)
> +
Idem combine with LTC4245_CURRENT_ALARM please.
> +#define LTC4245_POWER_RO(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_power, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_VOLTAGE_ALARM(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_voltage_alarm, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_CURRENT_ALARM(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_current_alarm, NULL, ltc4245_cmd_idx)
> +
> +#define LTC4245_POWER_ALARM(name, ltc4245_cmd_idx) \
> + static SENSOR_DEVICE_ATTR(name, S_IRUGO, \
> + ltc4245_show_power_alarm, NULL, ltc4245_cmd_idx)
> +
These 3 should be removed then.
<snip>
Well still some work to do, but we are definitely getting there. I think the
3th revision will be "perfect".
Regards,
Hans
