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SubjectRe: [RFC][PATCH] hwmon: (pmbus) Support 4th PSU temperature sensor
Date
On 7/28/21 2:38 AM, Paul Menzel wrote:
> From: Madhava Reddy Siddareddygari <msiddare@cisco.com>
>
> PSU650W has four temperature sensors, while the pmbus driver currently
> only support three temperature sensors.
>
> So, support a fourth temp sensor, i. e. PSU outlet temperature sensor,
> by copying what is done for temperature sensor 3, and use register 0xDF.
>
> PSU650W is based on LITE-ON vendor.
> LITE-ON MFG part numbers for the PSU are PS-2651-3SB5 Z and PS-2651-3SA5 Z.
>
> Signed-off-by: Madhava Reddy Siddareddygari <msiddare@cisco.com>
> Signed-off-by: Venkat Garigipati <venkatg@cisco.com>
> Cc: Billie Alsup <balsup@cisco.com>
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
> ---
> This as a RFC, as we know 0xDF is a manufacturer specific register, and
> cannot be added to the PMBus core driver. It was submitted to SONiC [1]
> by Cisco engineers.
>
> It’d be great if the maintainers good suggest how to easily implement a
> custom driver for that PSU?
>

Implement a chip driver with a set of read/write functions.
Claim it has two pages, with the second page only implementing a single
temperature sensor. In the read/write functions, handle page 0 normally,
and access the second sensor whenever page 1 is accessed.

> [1]: https://github.com/Azure/sonic-linux-kernel/pull/214

The comments there are a bit concerning.

"* Virtual registers.
* Useful to support attributes which are not supported by standard PMBus
* registers but exist as manufacturer specific registers on individual chips.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
* Must be mapped to real registers in device specific code.
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
"

Then,

"... is Manufacturer specific command. These are not Virtual registers."

Isn't that exactly what the "Virtual registers" description states ?
How can that be explained better ?

Either case, I see no need to define a virtual register for a 4th temperature
sensor. This can easily be implemented with the mechanism described above.

Guenter

>
> drivers/hwmon/pmbus/pmbus.c | 4 +++-
> drivers/hwmon/pmbus/pmbus.h | 3 +++
> drivers/hwmon/pmbus/pmbus_core.c | 38 ++++++++++++++++++++++++++++++++
> 3 files changed, 44 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/hwmon/pmbus/pmbus.c b/drivers/hwmon/pmbus/pmbus.c
> index d0d386990af5..df2a782a1105 100644
> --- a/drivers/hwmon/pmbus/pmbus.c
> +++ b/drivers/hwmon/pmbus/pmbus.c
> @@ -60,8 +60,10 @@ static void pmbus_find_sensor_groups(struct i2c_client *client,
> info->func[0] |= PMBUS_HAVE_TEMP2;
> if (pmbus_check_word_register(client, 0, PMBUS_READ_TEMPERATURE_3))
> info->func[0] |= PMBUS_HAVE_TEMP3;
> + if (pmbus_check_word_register(client, 0, PMBUS_READ_TEMPERATURE_4))
> + info->func[0] |= PMBUS_HAVE_TEMP4;
> if (info->func[0] & (PMBUS_HAVE_TEMP | PMBUS_HAVE_TEMP2
> - | PMBUS_HAVE_TEMP3)
> + | PMBUS_HAVE_TEMP3 | PMBUS_HAVE_TEMP4)
> && pmbus_check_byte_register(client, 0,
> PMBUS_STATUS_TEMPERATURE))
> info->func[0] |= PMBUS_HAVE_STATUS_TEMP;
> diff --git a/drivers/hwmon/pmbus/pmbus.h b/drivers/hwmon/pmbus/pmbus.h
> index e0aa8aa46d8c..1522c8c7cade 100644
> --- a/drivers/hwmon/pmbus/pmbus.h
> +++ b/drivers/hwmon/pmbus/pmbus.h
> @@ -135,6 +135,8 @@ enum pmbus_regs {
> PMBUS_MFR_MAX_TEMP_2 = 0xC1,
> PMBUS_MFR_MAX_TEMP_3 = 0xC2,
>
> + PMBUS_READ_TEMPERATURE_4 = 0xDF,
> +
> /*
> * Virtual registers.
> * Useful to support attributes which are not supported by standard PMBus
> @@ -401,6 +403,7 @@ enum pmbus_sensor_classes {
> #define PMBUS_HAVE_PWM12 BIT(20)
> #define PMBUS_HAVE_PWM34 BIT(21)
> #define PMBUS_HAVE_SAMPLES BIT(22)
> +#define PMBUS_HAVE_TEMP4 BIT(23)
>
> #define PMBUS_PHASE_VIRTUAL BIT(30) /* Phases on this page are virtual */
> #define PMBUS_PAGE_VIRTUAL BIT(31) /* Page is virtual */
> diff --git a/drivers/hwmon/pmbus/pmbus_core.c b/drivers/hwmon/pmbus/pmbus_core.c
> index 776ee2237be2..b084b5ba6d45 100644
> --- a/drivers/hwmon/pmbus/pmbus_core.c
> +++ b/drivers/hwmon/pmbus/pmbus_core.c
> @@ -1810,6 +1810,32 @@ static const struct pmbus_limit_attr temp_limit_attrs3[] = {
> },
> };
>
> +static const struct pmbus_limit_attr temp_limit_attrs4[] = {
> + {
> + .reg = PMBUS_UT_WARN_LIMIT,
> + .low = true,
> + .attr = "min",
> + .alarm = "min_alarm",
> + .sbit = PB_TEMP_UT_WARNING,
> + }, {
> + .reg = PMBUS_UT_FAULT_LIMIT,
> + .low = true,
> + .attr = "lcrit",
> + .alarm = "lcrit_alarm",
> + .sbit = PB_TEMP_UT_FAULT,
> + }, {
> + .reg = PMBUS_OT_WARN_LIMIT,
> + .attr = "max",
> + .alarm = "max_alarm",
> + .sbit = PB_TEMP_OT_WARNING,
> + }, {
> + .reg = PMBUS_OT_FAULT_LIMIT,
> + .attr = "crit",
> + .alarm = "crit_alarm",
> + .sbit = PB_TEMP_OT_FAULT,
> + }
> +};
> +
> static const struct pmbus_sensor_attr temp_attributes[] = {
> {
> .reg = PMBUS_READ_TEMPERATURE_1,
> @@ -1847,6 +1873,18 @@ static const struct pmbus_sensor_attr temp_attributes[] = {
> .gbit = PB_STATUS_TEMPERATURE,
> .limit = temp_limit_attrs3,
> .nlimit = ARRAY_SIZE(temp_limit_attrs3),
> + }, {
> + .reg = PMBUS_READ_TEMPERATURE_4,
> + .class = PSC_TEMPERATURE,
> + .paged = true,
> + .update = true,
> + .compare = true,
> + .func = PMBUS_HAVE_TEMP4,
> + .sfunc = PMBUS_HAVE_STATUS_TEMP,
> + .sbase = PB_STATUS_TEMP_BASE,
> + .gbit = PB_STATUS_TEMPERATURE,
> + .limit = temp_limit_attrs4,
> + .nlimit = ARRAY_SIZE(temp_limit_attrs4),
> }
> };
>
>

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