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[ Upstream commit084ed144c4] The JC42 compatible thermal sensor on Kingston KSM32ES8/16ME DIMMs (using Micron E-Die) is an ST Microelectronics STTS2004 (manufacturer 0x104a, device 0x2201). It does not keep the previously programmed minimum, maximum and critical temperatures after system suspend and resume (which is a shutdown / startup cycle for the JC42 temperature sensor). This results in an alarm on system resume because the hardware default for these values is 0°C (so any environment temperature greater than 0°C will trigger the alarm). Example before system suspend: jc42-i2c-0-1a Adapter: SMBus PIIX4 adapter port 0 at 0b00 temp1: +34.8°C (low = +0.0°C) (high = +85.0°C, hyst = +85.0°C) (crit = +95.0°C, hyst = +95.0°C) Example after system resume (without this change): jc42-i2c-0-1a Adapter: SMBus PIIX4 adapter port 0 at 0b00 temp1: +34.8°C (low = +0.0°C) ALARM (HIGH, CRIT) (high = +0.0°C, hyst = +0.0°C) (crit = +0.0°C, hyst = +0.0°C) Apply the cached values from the JC42_REG_TEMP_UPPER, JC42_REG_TEMP_LOWER, JC42_REG_TEMP_CRITICAL and JC42_REG_SMBUS (where the SMBUS register is not related to this issue but a side-effect of using regcache_sync() during system resume with the previously cached/programmed values. This fixes the alarm due to the hardware defaults of 0°C because the previously applied limits (set by userspace) are re-applied on system resume. Fixes:175c490c9e("hwmon: (jc42) Add support for STTS2004 and AT30TSE004") Reviewed-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com> Link: https://lore.kernel.org/r/20221023213157.11078-3-martin.blumenstingl@googlemail.com Signed-off-by: Guenter Roeck <linux@roeck-us.net> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.