Commit 084ed144 authored by Martin Blumenstingl's avatar Martin Blumenstingl Committed by Guenter Roeck
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hwmon: (jc42) Restore the min/max/critical temperatures on resume 



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: 175c490c ("hwmon: (jc42) Add support for STTS2004 and AT30TSE004")
Reviewed-by: default avatarGuenter Roeck <linux@roeck-us.net>
Signed-off-by: default avatarMartin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20221023213157.11078-3-martin.blumenstingl@googlemail.com


Signed-off-by: default avatarGuenter Roeck <linux@roeck-us.net>
parent 8f2fa472

drivers/hwmon/jc42.c

+9 −1
Original line number Diff line number Diff line
@@ -578,6 +578,10 @@ static int jc42_suspend(struct device *dev) 


	data->config |= JC42_CFG_SHUTDOWN;

	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);



	regcache_cache_only(data->regmap, true);

	regcache_mark_dirty(data->regmap);



	return 0;

}
@@ -585,9 +589,13 @@ static int jc42_resume(struct device *dev) 
{

	struct jc42_data *data = dev_get_drvdata(dev);



	regcache_cache_only(data->regmap, false);



	data->config &= ~JC42_CFG_SHUTDOWN;

	regmap_write(data->regmap, JC42_REG_CONFIG, data->config);

	return 0;



	/* Restore cached register values to hardware */

	return regcache_sync(data->regmap);

}



static const struct dev_pm_ops jc42_dev_pm_ops = {