diff mbox series

[v5,1/3] thermal/acpi: Add ACPI trip point routines

Message ID 20230113180235.1604526-2-daniel.lezcano@linaro.org (mailing list archive)
State Changes Requested, archived
Headers show
Series Thermal ACPI APIs for generic trip points | expand

Commit Message

Daniel Lezcano Jan. 13, 2023, 6:02 p.m. UTC 
The ACPI specification describes the trip points, the device tree
bindings as well.

The OF code uses the generic trip point structures.

The ACPI has their own trip points structure and uses the get_trip_*
ops to retrieve them.

We can do the same as the OF code and create a set of ACPI functions
to retrieve a trip point description. Having a common code for ACPI
will help to cleanup the remaining Intel drivers and get rid of the
get_trip_* functions.

These changes add the ACPI thermal calls to retrieve the basic
information we need to be reused in the thermal ACPI and Intel
drivers.

The different ACPI functions have the generic trip point structure
passed as parameter where it is filled.

This structure aims to be the one used by all the thermal drivers and
the thermal framework.

After this series, a couple of Intel drivers and the ACPI thermal
driver will still have their own trip points definition but a new
series on top of this one will finish the conversion to the generic
trip point handling.

This series depends on the generic trip point added to the thermal
framework and available in the thermal/linux-next branch.

 https://lkml.org/lkml/2022/10/3/456

It has been tested on a Intel i7-8650U - x280 with the INT3400, the
PCH, ACPITZ, and x86_pkg_temp. No regression observed so far.

Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
---
 drivers/thermal/Kconfig        |   4 +
 drivers/thermal/Makefile       |   1 +
 drivers/thermal/thermal_acpi.c | 209 +++++++++++++++++++++++++++++++++
 include/linux/thermal.h        |   8 ++
 4 files changed, 222 insertions(+)
 create mode 100644 drivers/thermal/thermal_acpi.c

Comments

Rafael J. Wysocki Jan. 19, 2023, 1:15 p.m. UTC | #1 
On Fri, Jan 13, 2023 at 7:02 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> The ACPI specification describes the trip points, the device tree
> bindings as well.
>
> The OF code uses the generic trip point structures.
>
> The ACPI has their own trip points structure and uses the get_trip_*
> ops to retrieve them.
>
> We can do the same as the OF code and create a set of ACPI functions
> to retrieve a trip point description. Having a common code for ACPI
> will help to cleanup the remaining Intel drivers and get rid of the
> get_trip_* functions.
>
> These changes add the ACPI thermal calls to retrieve the basic
> information we need to be reused in the thermal ACPI and Intel
> drivers.
>
> The different ACPI functions have the generic trip point structure
> passed as parameter where it is filled.
>
> This structure aims to be the one used by all the thermal drivers and
> the thermal framework.
>
> After this series, a couple of Intel drivers and the ACPI thermal
> driver will still have their own trip points definition but a new
> series on top of this one will finish the conversion to the generic
> trip point handling.
>
> This series depends on the generic trip point added to the thermal
> framework and available in the thermal/linux-next branch.
>
>  https://lkml.org/lkml/2022/10/3/456
>
> It has been tested on a Intel i7-8650U - x280 with the INT3400, the
> PCH, ACPITZ, and x86_pkg_temp. No regression observed so far.

Some names of the functions defined below can be less cryptic IMO.
Please see the following comments.

> Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
> ---
>  drivers/thermal/Kconfig        |   4 +
>  drivers/thermal/Makefile       |   1 +
>  drivers/thermal/thermal_acpi.c | 209 +++++++++++++++++++++++++++++++++
>  include/linux/thermal.h        |   8 ++
>  4 files changed, 222 insertions(+)
>  create mode 100644 drivers/thermal/thermal_acpi.c
>
> diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
> index e052dae614eb..eaeb2b2ee6e9 100644
> --- a/drivers/thermal/Kconfig
> +++ b/drivers/thermal/Kconfig
> @@ -76,6 +76,10 @@ config THERMAL_OF
>           Say 'Y' here if you need to build thermal infrastructure
>           based on device tree.
>
> +config THERMAL_ACPI
> +       depends on ACPI
> +       bool
> +
>  config THERMAL_WRITABLE_TRIPS
>         bool "Enable writable trip points"
>         help
> diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
> index 2506c6c8ca83..60f0dfa9aae2 100644
> --- a/drivers/thermal/Makefile
> +++ b/drivers/thermal/Makefile
> @@ -13,6 +13,7 @@ thermal_sys-$(CONFIG_THERMAL_NETLINK)         += thermal_netlink.o
>  # interface to/from other layers providing sensors
>  thermal_sys-$(CONFIG_THERMAL_HWMON)            += thermal_hwmon.o
>  thermal_sys-$(CONFIG_THERMAL_OF)               += thermal_of.o
> +thermal_sys-$(CONFIG_THERMAL_ACPI)             += thermal_acpi.o
>
>  # governors
>  thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)   += gov_fair_share.o
> diff --git a/drivers/thermal/thermal_acpi.c b/drivers/thermal/thermal_acpi.c
> new file mode 100644
> index 000000000000..ef6f10713650
> --- /dev/null
> +++ b/drivers/thermal/thermal_acpi.c
> @@ -0,0 +1,209 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Copyright 2022 Linaro Limited
> + *
> + * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
> + *
> + * ACPI thermal configuration
> + */
> +#include <linux/acpi.h>
> +#include <linux/module.h>
> +#include <linux/kernel.h>
> +#include <linux/units.h>
> +#include <uapi/linux/thermal.h>
> +
> +#include "thermal_core.h"
> +
> +/*
> + * An hysteresis value below zero is invalid and we can consider a
> + * value greater than 20°K/°C is invalid too.
> + */
> +#define HYSTERESIS_MIN_DECIK   0
> +#define HYSTERESIS_MAX_DECIK   200

If the full word "hysteresis" is used here, it should also be used in
the hysteresis-related names below.

I would use the "hyst" abbreviation here and elsewhere where applicable.

> +
> +/*
> + * Minimum temperature for full military grade is 218°K (-55°C) and
> + * max temperature is 448°K (175°C). We can consider those values as
> + * the boundaries for the [trips] temperature returned by the
> + * firmware. Any values out of these boundaries can be considered
> + * bogus and we can assume the firmware has no data to provide.
> + */
> +#define TEMPERATURE_MIN_DECIK  2180
> +#define TEMPERATURE_MAX_DECIK  4480

Like the above, but regarding "temperature" and "temp" instead of
"hysteresis" and "hyst", respectively.

> +
> +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
> +                                              char *object, int *temperature)

So this would become thermal_acpi_get_temp_object(). or even
thermal_acpi_get_temp() because it really returns the temperature
value.

I also don't particularly like returning values via pointers, which is
entirely avoidable here, because the temperature value obtained from
the ACPI control methods must be a positive number.

So I would make it

static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
{

which would be consistent with the definition of the hysteresis
function below (which returns the value directly).

> +{
> +       unsigned long long temp;
> +       acpi_status status;
> +
> +       status = acpi_evaluate_integer(adev->handle, object, NULL, &temp);
> +       if (ACPI_FAILURE(status)) {
> +               acpi_handle_debug(adev->handle, "No temperature object '%s'\n", object);

This message may not be true, because status need not be AE_NOT_FOUND.

> +               return -ENODEV;
> +       }
> +
> +       if (temp < TEMPERATURE_MIN_DECIK || temp >= TEMPERATURE_MAX_DECIK) {
> +               acpi_handle_info(adev->handle, "Invalid temperature '%llu deci°K' for object '%s'\n",
> +                                temp, object);

I think that the message can be debug-level as well and I would just
say "Invalid value %llu returned by %s\n" in it.

> +               return -ENODATA;

And I'm not sure if the difference between -ENODEV and -ENODATA
matters here.  Maybe return -ENODATA in all error cases?

> +       }
> +
> +       *temperature = deci_kelvin_to_millicelsius(temp);
> +
> +       return 0;
> +}
> +
> +/**
> + * thermal_acpi_trip_gtsh() - Get the global hysteresis value

thermal_acpi_global_hyst() please.

> + * @adev: the acpi device to get the description from
> + *
> + * Get the global hysteresis value for the trip points. If any call
> + * fail, we shall return a zero hysteresis value.
> + *
> + * Return: An integer between %HYSTERESIS_MIN_DECIK and %HYSTERESIS_MAX_DECIK
> + */
> +int thermal_acpi_trip_gtsh(struct acpi_device *adev)
> +{
> +       unsigned long long hyst;
> +       acpi_status status;
> +
> +       status = acpi_evaluate_integer(adev->handle, "GTSH", NULL, &hyst);

GTSH is not a standard ACPI thing.

AFAICS, it's int3403 specific, so using it in a generic ACPI library
is questionable.

> +       if (ACPI_FAILURE(status))
> +               return 0;
> +
> +       if (hyst < HYSTERESIS_MIN_DECIK || hyst >= HYSTERESIS_MAX_DECIK) {
> +               acpi_handle_info(adev->handle, "Invalid hysteresis '%llu deci°K' for object 'GTSH'\n",
> +                                hyst);
> +               return 0;
> +       }
> +
> +       return deci_kelvin_to_millicelsius(hyst);
> +}
> +EXPORT_SYMBOL_GPL(thermal_acpi_trip_gtsh);
> +
> +/**
> + * thermal_acpi_trip_act() - Get the specified active trip point

thermal_acpi_active_trip_temp, please.

> + * @adev: the acpi device to get the description from

Please spell ACPI in capitals in all comments.

And I would say

@adev: Thermal zone ACPI device object

> + * @trip: a &struct thermal_trip to be filled if the function succeed

@trip: Trip point structure to be populated on success

> + * @id: an integer speciyfing the active trip point id

@id: Active cooling level (0 - 9)

> + *
> + * The function calls the ACPI framework to get the "_ACTx" objects
> + * which describe the active trip points.

No, it doesn't do that.  What it really does can be described as

"Evaluate the _ACx object for the thermal zone represented by @adev to
obtain the temperature of the active cooling trip point corresponding
to the active cooling level given by @id and initialize @trip as an
active trip point using that temperature value"

> The @id builds the "_ACTx"
> + * string with the numbered active trip point name. Then it fills the
> + * @trip structure with the information retrieved from those objects.
> + *
> + * Return:
> + * * 0 - Success
> + * * -ENODEV - Failed to retrieve the ACPI object
> + * * -ENODATA - The ACPI object value appears to be inconsistent
> + */
> +int thermal_acpi_trip_act(struct acpi_device *adev,
> +                         struct thermal_trip *trip, int id)
> +{
> +       char name[5];

char name[] = "_AC0";

> +       int ret;

int temp;

if (id < 0 || id > 9)
        return -EINVAL;

name[3] += id;

> +
> +       sprintf(name, "_AC%d", id);
> +
> +       ret = thermal_acpi_get_temperature_object(adev, name, &trip->temperature);
> +       if (ret)
> +               return ret;

temp = thermal_acpi_get_temp(adev, name);
if (temp < 0)
        return temp;

trip->temperature = temp;

And analogously below.

> +
> +       trip->hysteresis = 0;
> +       trip->type = THERMAL_TRIP_ACTIVE;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(thermal_acpi_trip_act);
> +
> +/**
> + * thermal_acpi_trip_psv() - Get the passive trip point

thermal_acpi_passive_trip_temp, please.

> + * @adev: the acpi device to get the description from
> + * @trip: a &struct thermal_trip to be filled if the function succeed

The same comments as above apply.

> + *
> + * The function calls the ACPI framework to get the "_PSV" object
> + * which describe the passive trip point. Then it fills the @trip
> + * structure with the information retrieved from those objects.

"Evaluate the _PSV object for the thermal zone represented by @adev to
obtain the temperature of the passive cooling trip point and
initialize @trip as a passive trip point using that temperature
value."

> + *
> + * Return:
> + * * 0 - Success
> + * * -ENODEV - Failed to retrieve the ACPI object
> + * * -ENODATA - The ACPI object value appears to be inconsistent
> + */
> +int thermal_acpi_trip_psv(struct acpi_device *adev, struct thermal_trip *trip)
> +{
> +       int ret;
> +
> +       ret = thermal_acpi_get_temperature_object(adev, "_PSV", &trip->temperature);
> +       if (ret)
> +               return ret;
> +
> +       trip->hysteresis = 0;
> +       trip->type = THERMAL_TRIP_PASSIVE;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(thermal_acpi_trip_psv);
> +
> +/**
> + * thermal_acpi_trip_hot() - Get the near critical trip point

thermal_acpi_hot_trip_temp, please.

> + * @adev: the acpi device to get the description from
> + * @trip: a &struct thermal_trip to be filled if the function succeed

The same comments as above apply.

> + *
> + * The function calls the ACPI framework to get the "_HOT" object
> + * which describe the hot trip point. Then it fills the @trip
> + * structure with the information retrieved from those objects.

"Evaluate the _HOT object for the thermal zone represented by @adev to
obtain the temperature of the trip point at which the system is
expected to be put into the S4 sleep state and initialize @trip as a
hot trip point using that temperature value."

> + *
> + * Return:
> + * * 0 - Success
> + * * -ENODEV - Failed to retrieve the ACPI object
> + * * -ENODATA - The ACPI object appears to be inconsistent
> + */
> +int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip)
> +{
> +       int ret;
> +
> +       ret = thermal_acpi_get_temperature_object(adev, "_HOT", &trip->temperature);
> +       if (ret)
> +               return ret;
> +
> +       trip->hysteresis = 0;
> +       trip->type = THERMAL_TRIP_HOT;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(thermal_acpi_trip_hot);
> +
> +/**
> + * thermal_acpi_trip_crit() - Get the critical trip point

thermal_acpi_crit_trip_temp, please.

> + * @adev: the acpi device to get the description from
> + * @trip: a &struct thermal_trip to be filled if the function succeed

The same comments as above apply.

> + *
> + * The function calls the ACPI framework to get the "_CRT" object
> + * which describe the critical trip point. Then it fills the @trip
> + * structure with the information retrieved from this object.

"Evaluate the _CRT object for the thermal zone represented by @adev to
obtain the temperature of the critical cooling trip point and
initialize @trip as a critical trip point using that temperature
value."

> + *
> + * Return:
> + * * 0 - Success
> + * * -ENODEV - Failed to retrieve the ACPI object
> + * * -ENODATA - The ACPI object value appears to be inconsistent
> + */
> +int thermal_acpi_trip_crit(struct acpi_device *adev, struct thermal_trip *trip)
> +{
> +       int ret;
> +
> +       ret = thermal_acpi_get_temperature_object(adev, "_CRT", &trip->temperature);
> +       if (ret)
> +               return ret;
> +
> +       /*
> +        * The hysteresis value has no sense here because critical
> +        * trip point has no u-turn
> +        */
> +       trip->hysteresis = 0;
> +       trip->type = THERMAL_TRIP_CRITICAL;
> +
> +       return 0;
> +}
> +EXPORT_SYMBOL_GPL(thermal_acpi_trip_crit);
> diff --git a/include/linux/thermal.h b/include/linux/thermal.h
> index 30353e4b1424..ba2d5d4c23e2 100644
> --- a/include/linux/thermal.h
> +++ b/include/linux/thermal.h
> @@ -334,6 +334,14 @@ static inline void devm_thermal_of_zone_unregister(struct device *dev,
>  }
>  #endif
>
> +#ifdef CONFIG_THERMAL_ACPI
> +int thermal_acpi_trip_gtsh(struct acpi_device *adev);
> +int thermal_acpi_trip_crit(struct acpi_device *adev, struct thermal_trip *trip);
> +int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip);
> +int thermal_acpi_trip_psv(struct acpi_device *adev, struct thermal_trip *trip);
> +int thermal_acpi_trip_act(struct acpi_device *adev, struct thermal_trip *trip, int id);
> +#endif
> +
>  int __thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
>                             struct thermal_trip *trip);
>  int thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
> --
Daniel Lezcano Jan. 20, 2023, 6:08 p.m. UTC | #2 
Hi Rafael,


On 19/01/2023 14:15, Rafael J. Wysocki wrote:

[ ... ]

>> +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
>> +                                              char *object, int *temperature)
> 
> So this would become thermal_acpi_get_temp_object(). or even
> thermal_acpi_get_temp() because it really returns the temperature
> value.
> 
> I also don't particularly like returning values via pointers, which is
> entirely avoidable here, because the temperature value obtained from
> the ACPI control methods must be a positive number.
> 
> So I would make it
> 
> static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
> {

We are converting decikelvin -> millicelsius. Even it is very unlikely, 
the result could be less than zero (eg. -1°C). We won't be able to 
differentiate -ENODATA with a negative value, no ?

In the future, it is possible we will have to deal with cold trip points 
in order to warm a board. May be we should don't care for now ?
Rafael J. Wysocki Jan. 20, 2023, 6:15 p.m. UTC | #3 
On Fri, Jan 20, 2023 at 7:08 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
>
> Hi Rafael,
>
>
> On 19/01/2023 14:15, Rafael J. Wysocki wrote:
>
> [ ... ]
>
> >> +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
> >> +                                              char *object, int *temperature)
> >
> > So this would become thermal_acpi_get_temp_object(). or even
> > thermal_acpi_get_temp() because it really returns the temperature
> > value.
> >
> > I also don't particularly like returning values via pointers, which is
> > entirely avoidable here, because the temperature value obtained from
> > the ACPI control methods must be a positive number.
> >
> > So I would make it
> >
> > static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
> > {
>
> We are converting decikelvin -> millicelsius. Even it is very unlikely,
> the result could be less than zero (eg. -1°C). We won't be able to
> differentiate -ENODATA with a negative value, no ?
>
> In the future, it is possible we will have to deal with cold trip points
> in order to warm a board. May be we should don't care for now ?

My point is that the ACPI specification mandates that the return
values be in deciK and so always non-negative.
Daniel Lezcano Jan. 20, 2023, 6:27 p.m. UTC | #4 
On 20/01/2023 19:15, Rafael J. Wysocki wrote:
> On Fri, Jan 20, 2023 at 7:08 PM Daniel Lezcano
> <daniel.lezcano@linaro.org> wrote:
>>
>>
>> Hi Rafael,
>>
>>
>> On 19/01/2023 14:15, Rafael J. Wysocki wrote:
>>
>> [ ... ]
>>
>>>> +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
>>>> +                                              char *object, int *temperature)
>>>
>>> So this would become thermal_acpi_get_temp_object(). or even
>>> thermal_acpi_get_temp() because it really returns the temperature
>>> value.
>>>
>>> I also don't particularly like returning values via pointers, which is
>>> entirely avoidable here, because the temperature value obtained from
>>> the ACPI control methods must be a positive number.
>>>
>>> So I would make it
>>>
>>> static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
>>> {
>>
>> We are converting decikelvin -> millicelsius. Even it is very unlikely,
>> the result could be less than zero (eg. -1°C). We won't be able to
>> differentiate -ENODATA with a negative value, no ?
>>
>> In the future, it is possible we will have to deal with cold trip points
>> in order to warm a board. May be we should don't care for now ?
> 
> My point is that the ACPI specification mandates that the return
> values be in deciK and so always non-negative.

I understand that but the code does:

static int thermal_acpi_get_temp(struct acpi_device *adev, char 
*object_name)
{
	...

	return deci_kelvin_to_millicelsius(temp);
}

All the callers do:

...

         ret = thermal_acpi_get_temp(adev, name);
         if (ret < 0)
		return ret;
	/* This could be an error
	 * or negative millicelsius temperature
	 */

	/* here we already have millicelsius */
         trip->temperature = ret;
...

So I guess we want to do:

...

         ret = thermal_acpi_get_temp(adev, name);
         if (ret < 0)
		return ret;

	/* we convert here instead in thermal_acpi_get_temp() */
         trip->temperature = deci_kelvin_to_millicelsius(ret);
...

Sounds good ?
Rafael J. Wysocki Jan. 20, 2023, 6:47 p.m. UTC | #5 
On Fri, Jan 20, 2023 at 7:27 PM Daniel Lezcano
<daniel.lezcano@linaro.org> wrote:
>
> On 20/01/2023 19:15, Rafael J. Wysocki wrote:
> > On Fri, Jan 20, 2023 at 7:08 PM Daniel Lezcano
> > <daniel.lezcano@linaro.org> wrote:
> >>
> >>
> >> Hi Rafael,
> >>
> >>
> >> On 19/01/2023 14:15, Rafael J. Wysocki wrote:
> >>
> >> [ ... ]
> >>
> >>>> +static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
> >>>> +                                              char *object, int *temperature)
> >>>
> >>> So this would become thermal_acpi_get_temp_object(). or even
> >>> thermal_acpi_get_temp() because it really returns the temperature
> >>> value.
> >>>
> >>> I also don't particularly like returning values via pointers, which is
> >>> entirely avoidable here, because the temperature value obtained from
> >>> the ACPI control methods must be a positive number.
> >>>
> >>> So I would make it
> >>>
> >>> static int thermal_acpi_get_temp(struct acpi_device *adev, char *object_name)
> >>> {
> >>
> >> We are converting decikelvin -> millicelsius. Even it is very unlikely,
> >> the result could be less than zero (eg. -1°C). We won't be able to
> >> differentiate -ENODATA with a negative value, no ?
> >>
> >> In the future, it is possible we will have to deal with cold trip points
> >> in order to warm a board. May be we should don't care for now ?
> >
> > My point is that the ACPI specification mandates that the return
> > values be in deciK and so always non-negative.
>
> I understand that but the code does:
>
> static int thermal_acpi_get_temp(struct acpi_device *adev, char
> *object_name)
> {
>         ...
>
>         return deci_kelvin_to_millicelsius(temp);
> }
>
> All the callers do:
>
> ...
>
>          ret = thermal_acpi_get_temp(adev, name);
>          if (ret < 0)
>                 return ret;
>         /* This could be an error
>          * or negative millicelsius temperature
>          */
>
>         /* here we already have millicelsius */
>          trip->temperature = ret;
> ...
>
> So I guess we want to do:
>
> ...
>
>          ret = thermal_acpi_get_temp(adev, name);
>          if (ret < 0)
>                 return ret;
>
>         /* we convert here instead in thermal_acpi_get_temp() */
>          trip->temperature = deci_kelvin_to_millicelsius(ret);
> ...
>
> Sounds good ?

Yes, it does.  Convert when it is known to be valid.
diff mbox series

Patch

diff --git a/drivers/thermal/Kconfig b/drivers/thermal/Kconfig
index e052dae614eb..eaeb2b2ee6e9 100644
--- a/drivers/thermal/Kconfig
+++ b/drivers/thermal/Kconfig
@@ -76,6 +76,10 @@  config THERMAL_OF
 	  Say 'Y' here if you need to build thermal infrastructure
 	  based on device tree.
 
+config THERMAL_ACPI
+       depends on ACPI
+       bool
+
 config THERMAL_WRITABLE_TRIPS
 	bool "Enable writable trip points"
 	help
diff --git a/drivers/thermal/Makefile b/drivers/thermal/Makefile
index 2506c6c8ca83..60f0dfa9aae2 100644
--- a/drivers/thermal/Makefile
+++ b/drivers/thermal/Makefile
@@ -13,6 +13,7 @@  thermal_sys-$(CONFIG_THERMAL_NETLINK)		+= thermal_netlink.o
 # interface to/from other layers providing sensors
 thermal_sys-$(CONFIG_THERMAL_HWMON)		+= thermal_hwmon.o
 thermal_sys-$(CONFIG_THERMAL_OF)		+= thermal_of.o
+thermal_sys-$(CONFIG_THERMAL_ACPI)		+= thermal_acpi.o
 
 # governors
 thermal_sys-$(CONFIG_THERMAL_GOV_FAIR_SHARE)	+= gov_fair_share.o
diff --git a/drivers/thermal/thermal_acpi.c b/drivers/thermal/thermal_acpi.c
new file mode 100644
index 000000000000..ef6f10713650
--- /dev/null
+++ b/drivers/thermal/thermal_acpi.c
@@ -0,0 +1,209 @@ 
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright 2022 Linaro Limited
+ *
+ * Author: Daniel Lezcano <daniel.lezcano@linaro.org>
+ *
+ * ACPI thermal configuration
+ */
+#include <linux/acpi.h>
+#include <linux/module.h>
+#include <linux/kernel.h>
+#include <linux/units.h>
+#include <uapi/linux/thermal.h>
+
+#include "thermal_core.h"
+
+/*
+ * An hysteresis value below zero is invalid and we can consider a
+ * value greater than 20°K/°C is invalid too.
+ */
+#define HYSTERESIS_MIN_DECIK	0
+#define HYSTERESIS_MAX_DECIK	200
+
+/*
+ * Minimum temperature for full military grade is 218°K (-55°C) and
+ * max temperature is 448°K (175°C). We can consider those values as
+ * the boundaries for the [trips] temperature returned by the
+ * firmware. Any values out of these boundaries can be considered
+ * bogus and we can assume the firmware has no data to provide.
+ */
+#define TEMPERATURE_MIN_DECIK	2180
+#define TEMPERATURE_MAX_DECIK	4480
+
+static int thermal_acpi_get_temperature_object(struct acpi_device *adev,
+					       char *object, int *temperature)
+{
+	unsigned long long temp;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(adev->handle, object, NULL, &temp);
+	if (ACPI_FAILURE(status)) {
+		acpi_handle_debug(adev->handle, "No temperature object '%s'\n", object);
+		return -ENODEV;
+	}
+
+	if (temp < TEMPERATURE_MIN_DECIK || temp >= TEMPERATURE_MAX_DECIK) {
+		acpi_handle_info(adev->handle, "Invalid temperature '%llu deci°K' for object '%s'\n",
+				 temp, object);
+		return -ENODATA;
+	}
+
+	*temperature = deci_kelvin_to_millicelsius(temp);
+
+	return 0;
+}
+
+/**
+ * thermal_acpi_trip_gtsh() - Get the global hysteresis value
+ * @adev: the acpi device to get the description from
+ *
+ * Get the global hysteresis value for the trip points. If any call
+ * fail, we shall return a zero hysteresis value.
+ *
+ * Return: An integer between %HYSTERESIS_MIN_DECIK and %HYSTERESIS_MAX_DECIK
+ */
+int thermal_acpi_trip_gtsh(struct acpi_device *adev)
+{
+	unsigned long long hyst;
+	acpi_status status;
+
+	status = acpi_evaluate_integer(adev->handle, "GTSH", NULL, &hyst);
+	if (ACPI_FAILURE(status))
+		return 0;
+
+	if (hyst < HYSTERESIS_MIN_DECIK || hyst >= HYSTERESIS_MAX_DECIK) {
+		acpi_handle_info(adev->handle, "Invalid hysteresis '%llu deci°K' for object 'GTSH'\n",
+				 hyst);
+		return 0;
+	}
+
+	return deci_kelvin_to_millicelsius(hyst);
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_gtsh);
+
+/**
+ * thermal_acpi_trip_act() - Get the specified active trip point
+ * @adev: the acpi device to get the description from
+ * @trip: a &struct thermal_trip to be filled if the function succeed
+ * @id: an integer speciyfing the active trip point id
+ *
+ * The function calls the ACPI framework to get the "_ACTx" objects
+ * which describe the active trip points. The @id builds the "_ACTx"
+ * string with the numbered active trip point name. Then it fills the
+ * @trip structure with the information retrieved from those objects.
+ *
+ * Return:
+ * * 0 - Success
+ * * -ENODEV - Failed to retrieve the ACPI object
+ * * -ENODATA - The ACPI object value appears to be inconsistent
+ */
+int thermal_acpi_trip_act(struct acpi_device *adev,
+			  struct thermal_trip *trip, int id)
+{
+	char name[5];
+	int ret;
+
+	sprintf(name, "_AC%d", id);
+
+	ret = thermal_acpi_get_temperature_object(adev, name, &trip->temperature);
+	if (ret)
+		return ret;
+
+	trip->hysteresis = 0;
+	trip->type = THERMAL_TRIP_ACTIVE;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_act);
+
+/**
+ * thermal_acpi_trip_psv() - Get the passive trip point
+ * @adev: the acpi device to get the description from
+ * @trip: a &struct thermal_trip to be filled if the function succeed
+ *
+ * The function calls the ACPI framework to get the "_PSV" object
+ * which describe the passive trip point. Then it fills the @trip
+ * structure with the information retrieved from those objects.
+ *
+ * Return:
+ * * 0 - Success
+ * * -ENODEV - Failed to retrieve the ACPI object
+ * * -ENODATA - The ACPI object value appears to be inconsistent
+ */
+int thermal_acpi_trip_psv(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	int ret;
+
+	ret = thermal_acpi_get_temperature_object(adev, "_PSV", &trip->temperature);
+	if (ret)
+		return ret;
+
+	trip->hysteresis = 0;
+	trip->type = THERMAL_TRIP_PASSIVE;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_psv);
+
+/**
+ * thermal_acpi_trip_hot() - Get the near critical trip point
+ * @adev: the acpi device to get the description from
+ * @trip: a &struct thermal_trip to be filled if the function succeed
+ *
+ * The function calls the ACPI framework to get the "_HOT" object
+ * which describe the hot trip point. Then it fills the @trip
+ * structure with the information retrieved from those objects.
+ *
+ * Return:
+ * * 0 - Success
+ * * -ENODEV - Failed to retrieve the ACPI object
+ * * -ENODATA - The ACPI object appears to be inconsistent
+ */
+int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	int ret;
+
+	ret = thermal_acpi_get_temperature_object(adev, "_HOT", &trip->temperature);
+	if (ret)
+		return ret;
+
+	trip->hysteresis = 0;
+	trip->type = THERMAL_TRIP_HOT;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_hot);
+
+/**
+ * thermal_acpi_trip_crit() - Get the critical trip point
+ * @adev: the acpi device to get the description from
+ * @trip: a &struct thermal_trip to be filled if the function succeed
+ *
+ * The function calls the ACPI framework to get the "_CRT" object
+ * which describe the critical trip point. Then it fills the @trip
+ * structure with the information retrieved from this object.
+ *
+ * Return:
+ * * 0 - Success
+ * * -ENODEV - Failed to retrieve the ACPI object
+ * * -ENODATA - The ACPI object value appears to be inconsistent
+ */
+int thermal_acpi_trip_crit(struct acpi_device *adev, struct thermal_trip *trip)
+{
+	int ret;
+
+	ret = thermal_acpi_get_temperature_object(adev, "_CRT", &trip->temperature);
+	if (ret)
+		return ret;
+
+	/*
+	 * The hysteresis value has no sense here because critical
+	 * trip point has no u-turn
+	 */
+	trip->hysteresis = 0;
+	trip->type = THERMAL_TRIP_CRITICAL;
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(thermal_acpi_trip_crit);
diff --git a/include/linux/thermal.h b/include/linux/thermal.h
index 30353e4b1424..ba2d5d4c23e2 100644
--- a/include/linux/thermal.h
+++ b/include/linux/thermal.h
@@ -334,6 +334,14 @@  static inline void devm_thermal_of_zone_unregister(struct device *dev,
 }
 #endif
 
+#ifdef CONFIG_THERMAL_ACPI
+int thermal_acpi_trip_gtsh(struct acpi_device *adev);
+int thermal_acpi_trip_crit(struct acpi_device *adev, struct thermal_trip *trip);
+int thermal_acpi_trip_hot(struct acpi_device *adev, struct thermal_trip *trip);
+int thermal_acpi_trip_psv(struct acpi_device *adev, struct thermal_trip *trip);
+int thermal_acpi_trip_act(struct acpi_device *adev, struct thermal_trip *trip, int id);
+#endif
+
 int __thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,
 			    struct thermal_trip *trip);
 int thermal_zone_get_trip(struct thermal_zone_device *tz, int trip_id,