Re: [PATCH v2 3/6] hwmon: (pmbus/pim4328) Add support for reading direct format coefficients
From: Guenter Roeck
Date: Sun May 23 2021 - 15:48:02 EST
On 5/23/21 10:52 AM, Erik Rosen wrote:
On Sat, May 22, 2021 at 3:41 PM Guenter Roeck <linux@xxxxxxxxxxxx> wrote:
On 5/22/21 3:55 AM, Erik Rosen wrote:
Add support for reading and decoding direct format coefficients to
the PMBus core driver. If the new flag PMBUS_USE_COEFFICIENTS_CMD
is set, the driver will use the COEFFICIENTS register together with
the information in the pmbus_sensor_attr structs to initialize
relevant coefficients for the direct mode format.
Signed-off-by: Erik Rosen <erik.rosen@xxxxxxxxxxxxx>
---
drivers/hwmon/pmbus/pmbus_core.c | 93 ++++++++++++++++++++++++++++++++
include/linux/pmbus.h | 8 +++
2 files changed, 101 insertions(+)
diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
index 460cbfd716e4..03c169bf5633 100644
--- a/drivers/hwmon/pmbus/pmbus_core.c
+++ b/drivers/hwmon/pmbus/pmbus_core.c
@@ -2177,6 +2177,38 @@ static int pmbus_find_attributes(struct i2c_client *client,
return ret;
}
+static int pmbus_init_coefficients(struct i2c_client *client,
+ struct pmbus_data *data, int page,
This seems wrong. Coefficients are not maintained per page but per class,
and (re-)reading them for each supported page doesn't really add value or
even make sense.
+ enum pmbus_sensor_classes sensor_class,
+ const struct pmbus_sensor_attr *attrs,
+ int nattrs)
+{
+ int i, status;
+
+ for (i = 0; i < nattrs; i++) {
+ if (attrs->class == sensor_class &&
+ (attrs->func & data->info->func[page])) {
+ status = pmbus_read_coefficients(client,
+ (struct pmbus_driver_info *)data->info,
+ sensor_class,
+ attrs->reg);
+ if (status < 0) {
+ dev_err(&client->dev,
+ "Failed to read coefficients for register: %x\n",
+ attrs->reg);
+ return status;
+ }
+ return 0;
+ }
+ attrs++;
+ }
+
+ dev_err(&client->dev, "No coefficients found for register: %x\n",
+ attrs->reg);
+
attrs points beyond the array size here, so attrs->reg does not point
to a valid array element. The problem would also not be the register
this happens to point to, but the class (ie the chip does not support
a sensor of the requested class).
Not sure if this should trigger a message or error in the first place.
It won't matter since the chip will never need those coefficients.
If anything, this would be a misconfiguration (the driver should
not set direct format for this sensor class), and the return value
should be -EINVAL.
Either case, I wonder if this can be handled with less complex code,
ie without having to check data->info->func[] for all pages. How
about just walking through attrs and try all class matches until
one is found that works (ie not return on error but keep trying) ?
Ok, I'll send a new version based on your comments.
I'm not entirely comfortable with just silently ignoring any failure to
retrieve the coefficients for a sensor class. I mean it could be due to any
reason; a bus error for instance. I'll return a -EINVAL for now if you don't
disagree.
Ok. After all, it does suggest a misconfiguration.
Thanks,
Guenter
/Erik
+ return -ENODEV;
+}
+
/*
* Identify chip parameters.
* This function is called for all chips.
@@ -2185,6 +2217,7 @@ static int pmbus_identify_common(struct i2c_client *client,
struct pmbus_data *data, int page)
{
int vout_mode = -1;
+ int ret;
if (pmbus_check_byte_register(client, page, PMBUS_VOUT_MODE))
vout_mode = _pmbus_read_byte_data(client, page,
@@ -2214,6 +2247,66 @@ static int pmbus_identify_common(struct i2c_client *client,
}
}
+ if (data->flags & PMBUS_USE_COEFFICIENTS_CMD) {
I think there should be a separate function to handle that,
to be called only once, not once per page.
+ if (!i2c_check_functionality(client->adapter,
+ I2C_FUNC_SMBUS_BLOCK_PROC_CALL))
+ return -ENODEV;
+
+ if (data->info->format[PSC_VOLTAGE_IN] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_VOLTAGE_IN,
+ voltage_attributes,
+ ARRAY_SIZE(voltage_attributes));
+ if (ret)
+ return ret;
+ }
It might be useful to have a little structure with {class, attribute list pointer,
attribute list size} and walk through that in a loop instead of repeating essentially
the same code multiple times.
+
+ if (data->info->format[PSC_VOLTAGE_OUT] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_VOLTAGE_OUT,
+ voltage_attributes,
+ ARRAY_SIZE(voltage_attributes));
+ if (ret)
+ return ret;
+ }
+
+ if (data->info->format[PSC_CURRENT_IN] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_CURRENT_IN,
+ current_attributes,
+ ARRAY_SIZE(current_attributes));
+ if (ret)
+ return ret;
+ }
+
+ if (data->info->format[PSC_CURRENT_OUT] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_CURRENT_OUT,
+ current_attributes,
+ ARRAY_SIZE(current_attributes));
+ if (ret)
+ return ret;
+ }
+
+ if (data->info->format[PSC_POWER] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_POWER,
+ power_attributes,
+ ARRAY_SIZE(power_attributes));
+ if (ret)
+ return ret;
+ }
+
+ if (data->info->format[PSC_TEMPERATURE] == direct) {
+ ret = pmbus_init_coefficients(client, data, page,
+ PSC_TEMPERATURE,
+ temp_attributes,
+ ARRAY_SIZE(temp_attributes));
+ if (ret)
+ return ret;
+ }
+ }
+
pmbus_clear_fault_page(client, page);
return 0;
}
diff --git a/include/linux/pmbus.h b/include/linux/pmbus.h
index f720470b1bab..7fdc282dab5a 100644
--- a/include/linux/pmbus.h
+++ b/include/linux/pmbus.h
@@ -52,6 +52,14 @@
*/
#define PMBUS_NO_WRITE_PROTECT BIT(4)
+/*
+ * PMBUS_USE_COEFFICIENTS_CMD
+ *
+ * When this flag is set the PMBus core driver will use the COEFFICIENTS
+ * register to initialize the coefficients for the direct mode format.
+ */
+#define PMBUS_USE_COEFFICIENTS_CMD BIT(5)
+
struct pmbus_platform_data {
u32 flags; /* Device specific flags */