[PATCH 6.0 0464/1073] hwmon: (jc42) Restore the min/max/critical temperatures on resume

Greg Kroah-Hartman
2022-12-28T15:54:37Z

From: Martin Blumenstingl <martin.blumenstingl@googlemail.com>

[ Upstream commit 084ed144c448fd5bc8ed5a58247153fbbfd115c3 ]

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: 175c490c9e7f ("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>
---
drivers/hwmon/jc42.c | 10 +++++++++-
1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/drivers/hwmon/jc42.c b/drivers/hwmon/jc42.c
index 96bffd5b5866..5004b17c5682 100644
--- a/drivers/hwmon/jc42.c
+++ b/drivers/hwmon/jc42.c
@@ -579,6 +579,10 @@ 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;
}

@@ -586,9 +590,13 @@ 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 = {
--
2.35.1