[PATCH 4/9] i8k: Rework error retries

Pali Rohár
2015-01-12T13:32:53Z

From: Guenter Roeck <linux@roeck-us.net>

Instead of returning a previous value if the SMM code returns
an error when trying to read a temperature, retry once.
If that fails again, return -ENODATA. Also return -ENODATA if an
attempt is made to read the GPU temperature but the GPU is
currently turned off.

Drop the I8K_TEMPERATURE_BUG definition and handle the related bug
unconditionally.

Signed-off-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Pali Rohár <pali.rohar@gmail.com>
---
drivers/char/i8k.c | 47 ++++++++++++++++++++++++-----------------------
1 file changed, 24 insertions(+), 23 deletions(-)

diff --git a/drivers/char/i8k.c b/drivers/char/i8k.c
index 1854fab..0e332fc 100644
--- a/drivers/char/i8k.c
+++ b/drivers/char/i8k.c
@@ -5,7 +5,7 @@
*
* Hwmon integration:
* Copyright (C) 2011 Jean Delvare <jdelvare@suse.de>
- * Copyright (C) 2013 Guenter Roeck <linux@roeck-us.net>
+ * Copyright (C) 2013, 2014 Guenter Roeck <linux@roeck-us.net>
*
* This program is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License as published by the
@@ -20,6 +20,7 @@

#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

+#include <linux/delay.h>
#include <linux/module.h>
#include <linux/types.h>
#include <linux/init.h>
@@ -59,8 +60,6 @@
#define I8K_POWER_AC 0x05
#define I8K_POWER_BATTERY 0x01

-#define I8K_TEMPERATURE_BUG 1
-
static DEFINE_MUTEX(i8k_mutex);
static char bios_version[4];
static struct device *i8k_hwmon_dev;
@@ -300,39 +299,41 @@ static int i8k_get_temp_type(int sensor)
/*
* Read the cpu temperature.
*/
-static int i8k_get_temp(int sensor)
+static int _i8k_get_temp(int sensor)
{
- struct smm_regs regs = { .eax = I8K_SMM_GET_TEMP, };
- int rc;
- int temp;
+ struct smm_regs regs = {
+ .eax = I8K_SMM_GET_TEMP,
+ .ebx = sensor & 0xff,
+ };

-#ifdef I8K_TEMPERATURE_BUG
- static int prev[4] = { I8K_MAX_TEMP+1, I8K_MAX_TEMP+1, I8K_MAX_TEMP+1, I8K_MAX_TEMP+1 };
-#endif
- regs.ebx = sensor & 0xff;
- rc = i8k_smm(&regs);
- if (rc < 0)
- return rc;
+ return i8k_smm(&regs) ? : regs.eax & 0xff;
+}

- temp = regs.eax & 0xff;
+static int i8k_get_temp(int sensor)
+{
+ int temp = _i8k_get_temp(sensor);

-#ifdef I8K_TEMPERATURE_BUG
/*
* Sometimes the temperature sensor returns 0x99, which is out of range.
- * In this case we return (once) the previous cached value. For example:
+ * In this case we retry (once) before returning an error.
# 1003655137 00000058 00005a4b
# 1003655138 00000099 00003a80 <--- 0x99 = 153 degrees
# 1003655139 00000054 00005c52
*/
- if (temp > I8K_MAX_TEMP) {
- temp = prev[sensor];
- prev[sensor] = I8K_MAX_TEMP+1;
- } else {
- prev[sensor] = temp;
+ if (temp == 0x99) {
+ msleep(100);
+ temp = _i8k_get_temp(sensor);
}
+ /*
+ * Return -ENODATA for all invalid temperatures.
+ *
+ * Known instances are the 0x99 value as seen above as well as
+ * 0xc1 (193), which may be returned when trying to read the GPU
+ * temperature if the system supports a GPU and it is currently
+ * turned off.
+ */
if (temp > I8K_MAX_TEMP)
return -ENODATA;
-#endif

return temp;
}
--
1.7.9.5