linux-kernel - Re: [PATCH v2 3/3] hwmon: (coretemp) Extend the bitmask to read temperature to 0xff

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Date: Sun, 28 Apr 2024 10:01:30 -0700
From: Guenter Roeck <linux@...ck-us.net>
To: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>
Cc: "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	Zhang Rui <rui.zhang@...el.com>, Jean Delvare <jdelvare@...e.com>,
	Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>,
	Lukasz Luba <lukasz.luba@....com>,
	Daniel Lezcano <daniel.lezcano@...aro.org>,
	linux-pm@...r.kernel.org, linux-hwmon@...r.kernel.org,
	linux-kernel@...r.kernel.org, Ricardo Neri <ricardo.neri@...el.com>
Subject: Re: [PATCH v2 3/3] hwmon: (coretemp) Extend the bitmask to read
 temperature to 0xff

On Thu, Apr 25, 2024 at 10:13:11AM -0700, Ricardo Neri wrote:
> The Intel Software Development manual defines the temperature digital
> readout as the bits [22:16] of the IA32_[PACKAGE]_THERM_STATUS registers.
> Bit 23 is specified as reserved.
> 
> In recent processors, however, the temperature digital readout uses bits
> [23:16]. In those processors, using the bitmask 0x7f would lead to
> incorrect readings if the temperature deviates from TjMax by more than
> 127 degrees Celsius.
> 
> Although not guaranteed, bit 23 is likely to be 0 in processors from a few
> generations ago. The temperature reading would still be correct in those
> processors when using a 0xff bitmask.
> 
> Model-specific provisions can be made for older processors in which bit 23
> is not 0 should the need arise.
> 
> Signed-off-by: Ricardo Neri <ricardo.neri-calderon@...ux.intel.com>

Applied.

Thanks,
Guenter