Hi Sören,
On Thu, Jan 30, 2014 at 05:13:42PM -0800, Sören Brinkmann wrote:
> Hi Guenther,
>
> I recently became aware of some weird behavior when using the UCD9000
> driver for voltage monitoring. We use that device on our zc706 Zynq
> platform to generate 5 voltage rails. Observing the voltages in Linux
> showed a correct value for rail 1 but a 2x error in in rails 2-3 and a
> 4x error in rail 5. Digging through specs, docs and sources I could
> track this down to this:
> - The PMBus core assumes one VOUT_MODE register per chip
> - UCD90120 has VOUT_MODE registers per rail
>
> In our setup we have an exponent of -14 for rail 1, -13 for rails 2-4 and
> -14 for rail 5. The PMBus core only reads and uses the first one and
> applies it to all rails.
>
> I'm not sure whether the UCD devices don't comply to spec or whether
> this is a bug in the PMBus core, either way, the reported values from
> the driver are prone to be wrong/scaled by an unknown factor.
>
The PMBus specification is sufficiently vague to ensure that pretty much
any interpretation of it is PMBus compliant.
> Is this somehow known behavior for which a workaround might be
> available? Otherwise, if you know how an acceptable solution might look
> like, I might find some time and give it a shot.
>
I think we may have to expand the driver to detect and configure the exponent
per rail/page. At least I can not think of another solution right now.
Can you test the patch below ? Completely untested, but it compiles.
It will likely need some refinement (for example, other chips may not even
have the VOUT_MODE command on non-zero pages), but should be useful for
testing.
Thanks,
Guenter
---
>From ac94470368c469d762242e73b71c0b07f3feb7fc Mon Sep 17 00:00:00 2001
From: Guenter Roeck <linux@xxxxxxxxxxxx>
Date: Thu, 30 Jan 2014 19:51:14 -0800
Subject: [PATCH] hwmon: (pmbus) Support per-page exponent in linear mode
Some chips use different exponents for sensors on different pages
or rails. Detect and store exponent per page to support this situation.
This fixes a problem with wrong voltages seen on UCD90120.
Signed-off-by: Guenter Roeck <linux@xxxxxxxxxxxx>
---
drivers/hwmon/pmbus/pmbus_core.c | 68 ++++++++++++++++++++------------------
1 file changed, 36 insertions(+), 32 deletions(-)
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 3cbf66e..291d11f 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -90,7 +90,8 @@ struct pmbus_data {
u32 flags; /* from platform data */
- int exponent; /* linear mode: exponent for output voltages */
+ int exponent[PMBUS_PAGES];
+ /* linear mode: exponent for output voltages */
const struct pmbus_driver_info *info;
@@ -410,7 +411,7 @@ static long pmbus_reg2data_linear(struct pmbus_data *data,
long val;
if (sensor->class == PSC_VOLTAGE_OUT) { /* LINEAR16 */
- exponent = data->exponent;
+ exponent = data->exponent[sensor->page];
mantissa = (u16) sensor->data;
} else { /* LINEAR11 */
exponent = ((s16)sensor->data) >> 11;
@@ -516,7 +517,7 @@ static long pmbus_reg2data(struct pmbus_data *data, struct pmbus_sensor *sensor)
#define MIN_MANTISSA (511 * 1000)
static u16 pmbus_data2reg_linear(struct pmbus_data *data,
- enum pmbus_sensor_classes class, long val)
+ struct pmbus_sensor *sensor, long val)
{
s16 exponent = 0, mantissa;
bool negative = false;
@@ -525,7 +526,7 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data,
if (val == 0)
return 0;
- if (class == PSC_VOLTAGE_OUT) {
+ if (sensor->class == PSC_VOLTAGE_OUT) {
/* LINEAR16 does not support negative voltages */
if (val < 0)
return 0;
@@ -534,10 +535,10 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data,
* For a static exponents, we don't have a choice
* but to adjust the value to it.
*/
- if (data->exponent < 0)
- val <<= -data->exponent;
+ if (data->exponent[sensor->page] < 0)
+ val <<= -data->exponent[sensor->page];
else
- val >>= data->exponent;
+ val >>= data->exponent[sensor->page];
val = DIV_ROUND_CLOSEST(val, 1000);
return val & 0xffff;
}
@@ -548,14 +549,14 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data,
}
/* Power is in uW. Convert to mW before converting. */
- if (class == PSC_POWER)
+ if (sensor->class == PSC_POWER)
val = DIV_ROUND_CLOSEST(val, 1000L);
/*
* For simplicity, convert fan data to milli-units
* before calculating the exponent.
*/
- if (class == PSC_FAN)
+ if (sensor->class == PSC_FAN)
val = val * 1000;
/* Reduce large mantissa until it fits into 10 bit */
@@ -585,22 +586,22 @@ static u16 pmbus_data2reg_linear(struct pmbus_data *data,
}
static u16 pmbus_data2reg_direct(struct pmbus_data *data,
- enum pmbus_sensor_classes class, long val)
+ struct pmbus_sensor *sensor, long val)
{
long m, b, R;
- m = data->info->m[class];
- b = data->info->b[class];
- R = data->info->R[class];
+ m = data->info->m[sensor->class];
+ b = data->info->b[sensor->class];
+ R = data->info->R[sensor->class];
/* Power is in uW. Adjust R and b. */
- if (class == PSC_POWER) {
+ if (sensor->class == PSC_POWER) {
R -= 3;
b *= 1000;
}
/* Calculate Y = (m * X + b) * 10^R */
- if (class != PSC_FAN) {
+ if (sensor->class != PSC_FAN) {
R -= 3; /* Adjust R and b for data in milli-units */
b *= 1000;
}
@@ -619,7 +620,7 @@ static u16 pmbus_data2reg_direct(struct pmbus_data *data,
}
static u16 pmbus_data2reg_vid(struct pmbus_data *data,
- enum pmbus_sensor_classes class, long val)
+ struct pmbus_sensor *sensor, long val)
{
val = clamp_val(val, 500, 1600);
@@ -627,20 +628,20 @@ static u16 pmbus_data2reg_vid(struct pmbus_data *data,
}
static u16 pmbus_data2reg(struct pmbus_data *data,
- enum pmbus_sensor_classes class, long val)
+ struct pmbus_sensor *sensor, long val)
{
u16 regval;
- switch (data->info->format[class]) {
+ switch (data->info->format[sensor->class]) {
case direct:
- regval = pmbus_data2reg_direct(data, class, val);
+ regval = pmbus_data2reg_direct(data, sensor, val);
break;
case vid:
- regval = pmbus_data2reg_vid(data, class, val);
+ regval = pmbus_data2reg_vid(data, sensor, val);
break;
case linear:
default:
- regval = pmbus_data2reg_linear(data, class, val);
+ regval = pmbus_data2reg_linear(data, sensor, val);
break;
}
return regval;
@@ -746,7 +747,7 @@ static ssize_t pmbus_set_sensor(struct device *dev,
return -EINVAL;
mutex_lock(&data->update_lock);
- regval = pmbus_data2reg(data, sensor->class, val);
+ regval = pmbus_data2reg(data, sensor, val);
ret = _pmbus_write_word_data(client, sensor->page, sensor->reg, regval);
if (ret < 0)
rv = ret;
@@ -1643,12 +1644,13 @@ static int pmbus_find_attributes(struct i2c_client *client,
* This function is called for all chips.
*/
static int pmbus_identify_common(struct i2c_client *client,
- struct pmbus_data *data)
+ struct pmbus_data *data, int page)
{
int vout_mode = -1;
- if (pmbus_check_byte_register(client, 0, PMBUS_VOUT_MODE))
- vout_mode = _pmbus_read_byte_data(client, 0, PMBUS_VOUT_MODE);
+ if (pmbus_check_byte_register(client, page, PMBUS_VOUT_MODE))
+ vout_mode = _pmbus_read_byte_data(client, page,
+ PMBUS_VOUT_MODE);
if (vout_mode >= 0 && vout_mode != 0xff) {
/*
* Not all chips support the VOUT_MODE command,
@@ -1659,7 +1661,7 @@ static int pmbus_identify_common(struct i2c_client *client,
if (data->info->format[PSC_VOLTAGE_OUT] != linear)
return -ENODEV;
- data->exponent = ((s8)(vout_mode << 3)) >> 3;
+ data->exponent[page] = ((s8)(vout_mode << 3)) >> 3;
break;
case 1: /* VID mode */
if (data->info->format[PSC_VOLTAGE_OUT] != vid)
@@ -1674,7 +1676,7 @@ static int pmbus_identify_common(struct i2c_client *client,
}
}
- pmbus_clear_fault_page(client, 0);
+ pmbus_clear_fault_page(client, page);
return 0;
}
@@ -1682,7 +1684,7 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
struct pmbus_driver_info *info)
{
struct device *dev = &client->dev;
- int ret;
+ int page, ret;
/*
* Some PMBus chips don't support PMBUS_STATUS_BYTE, so try
@@ -1715,10 +1717,12 @@ static int pmbus_init_common(struct i2c_client *client, struct pmbus_data *data,
return -ENODEV;
}
- ret = pmbus_identify_common(client, data);
- if (ret < 0) {
- dev_err(dev, "Failed to identify chip capabilities\n");
- return ret;
+ for (page = 0; page < info->pages; page++) {
+ ret = pmbus_identify_common(client, data, page);
+ if (ret < 0) {
+ dev_err(dev, "Failed to identify chip capabilities\n");
+ return ret;
+ }
}
return 0;
}
--
1.7.9.7
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