linux-kernel - Re: [PATCH v2 1/2] thermal: intel: int340x: Add throttling control interface to PTC

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Message-ID: <0dc5ad78ecd3e9a692c50ffb860bb1b0f93fef39.camel@intel.com>
Date: Mon, 16 Jun 2025 00:46:55 +0000
From: "Zhang, Rui" <rui.zhang@...el.com>
To: "srinivas.pandruvada@...ux.intel.com"
	<srinivas.pandruvada@...ux.intel.com>, "lukasz.luba@....com"
	<lukasz.luba@....com>, "rafael@...nel.org" <rafael@...nel.org>,
	"daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>
CC: "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v2 1/2] thermal: intel: int340x: Add throttling control
 interface to PTC

On Fri, 2025-06-13 at 14:49 -0700, Srinivas Pandruvada wrote:
> Firmware-based thermal temperature control loops may aggressively
> throttle performance to prevent temperature overshoots relative to the
> defined target temperature. This can negatively impact performance.
> User
> space may prefer to prioritize performance, even if it results in
> temperature overshoots with in acceptable range.
> 
> For example, user space might tolerate temperature overshoots when the
> device is placed on a desk, as opposed to when it's on a lap. To
> accommodate such scenarios, an optional attribute is provided to
> specify
> a tolerance level for temperature overshoots while maintaining
> acceptable
> performance.
> 
> Attribute:
> thermal_tolerance:

yeah, this is much better to me.

>  This attribute ranges from 0 to 7, where 0 represents
> the most aggressive control to avoid any temperature overshoots, and 7
> represents a more graceful approach, favoring performance even at the
> expense of temperature overshoots.
> Note: This level may not scale linearly. For example, a value of 3 does
> not
> necessarily imply a 50% improvement in performance compared to a value
> of
> 0.
> 
> Signed-off-by: Srinivas Pandruvada
> <srinivas.pandruvada@...ux.intel.com>

Reviewed-by: Zhang Rui <rui.zhang@...el.com>

-rui
> ---
> v2:
> - Changed commit description
> - Change "gain" to "thermal_tolerance" analogous to latency_tolerance.
> - Dropped "min_performance" attribute for next patch set
> 
>  Documentation/driver-api/thermal/intel_dptf.rst          | 9 +++++++++
>  .../intel/int340x_thermal/platform_temperature_control.c | 8 +++++++-
>  2 files changed, 16 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/driver-api/thermal/intel_dptf.rst
> b/Documentation/driver-api/thermal/intel_dptf.rst
> index ec5769accae0..c51ac793dc06 100644
> --- a/Documentation/driver-api/thermal/intel_dptf.rst
> +++ b/Documentation/driver-api/thermal/intel_dptf.rst
> @@ -206,6 +206,15 @@ All these controls needs admin privilege to
> update.
>  	Update a new temperature target in milli degree celsius for
> hardware to
>  	use for the temperature control.
>  
> +``thermal_tolerance`` (RW)
> +	This attribute ranges from 0 to 7, where 0 represents
> +	the most aggressive control to avoid any temperature
> overshoots, and
> +	7 represents a more graceful approach, favoring performance
> even at
> +	the expense of temperature overshoots.
> +	Note: This level may not scale linearly. For example, a value
> of 3 does
> +	not necessarily imply a 50% improvement in performance
> compared to a
> +	value of 0.
> +
>  Given that this is platform temperature control, it is expected that a
>  single user-level manager owns and manages the controls. If multiple
>  user-level software applications attempt to write different targets,
> it
> diff --git
> a/drivers/thermal/intel/int340x_thermal/platform_temperature_control.c
> b/drivers/thermal/intel/int340x_thermal/platform_temperature_control.c
> index 2d6504514893..7850e91a6e2c 100644
> ---
> a/drivers/thermal/intel/int340x_thermal/platform_temperature_control.c
> +++
> b/drivers/thermal/intel/int340x_thermal/platform_temperature_control.c
> @@ -49,7 +49,7 @@ struct mmio_reg {
>  };
>  
>  #define MAX_ATTR_GROUP_NAME_LEN	32
> -#define PTC_MAX_ATTRS		3
> +#define PTC_MAX_ATTRS		4
>  
>  struct ptc_data {
>  	u32 offset;
> @@ -57,6 +57,7 @@ struct ptc_data {
>  	struct attribute *ptc_attrs[PTC_MAX_ATTRS];
>  	struct device_attribute temperature_target_attr;
>  	struct device_attribute enable_attr;
> +	struct device_attribute thermal_tolerance_attr;
>  	char group_name[MAX_ATTR_GROUP_NAME_LEN];
>  };
>  
> @@ -78,6 +79,7 @@ static u32 ptc_offsets[PTC_MAX_INSTANCES] = {0x5B20,
> 0x5B28, 0x5B30};
>  static const char * const ptc_strings[] = {
>  	"temperature_target",
>  	"enable",
> +	"thermal_tolerance",
>  	NULL
>  };
>  
> @@ -177,6 +179,8 @@ PTC_SHOW(temperature_target);
>  PTC_STORE(temperature_target);
>  PTC_SHOW(enable);
>  PTC_STORE(enable);
> +PTC_SHOW(thermal_tolerance);
> +PTC_STORE(thermal_tolerance);
>  
>  #define ptc_init_attribute(_name)\
>  	do {\
> @@ -193,9 +197,11 @@ static int ptc_create_groups(struct pci_dev *pdev,
> int instance, struct ptc_data
>  
>  	ptc_init_attribute(temperature_target);
>  	ptc_init_attribute(enable);
> +	ptc_init_attribute(thermal_tolerance);
>  
>  	data->ptc_attrs[index++] = &data-
> >temperature_target_attr.attr;
>  	data->ptc_attrs[index++] = &data->enable_attr.attr;
> +	data->ptc_attrs[index++] = &data->thermal_tolerance_attr.attr;
>  	data->ptc_attrs[index] = NULL;
>  
>  	snprintf(data->group_name, MAX_ATTR_GROUP_NAME_LEN,