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Message-ID: <24ff79b6-29f5-6921-7418-9ba93bcf7193@roeck-us.net>
Date: Sat, 22 May 2021 06:41:31 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Erik Rosen <erik.rosen@...ormote.com>,
Jean Delvare <jdelvare@...e.com>,
Jonathan Corbet <corbet@....net>, linux-hwmon@...r.kernel.org,
linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 3/6] hwmon: (pmbus/pim4328) Add support for reading
direct format coefficients
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@...ormote.com>
> ---
> 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) ?
> + 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 */
>
>
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