From 5ce91714b0d8c0a3ff9b858966721f508351cf4c Mon Sep 17 00:00:00 2001 From: =?utf8?q?Pali=20Roh=C3=A1r?= Date: Sat, 18 Jun 2016 00:54:47 +0200 Subject: [PATCH] hwmon: (dell-smm) Cache fan_type() calls and change fan detection MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit On more Dell machines (e.g. Dell Precision M3800) fan_type() call is too expensive (CPU is too long in SMM mode) and cause kernel to hang. This is bug in Dell SMM or BIOS. This patch caches type for each fan (as it should not change) and changes the way how fan presense is detected. First it try function fan_status() as was before commit f989e55452c7 ("i8k: Add support for fan labels"). And if that fails fallback to fan_type(). *_status() functions can fail in case fan is not currently accessible (e.g. present on GPU which is currently turned off). Reported-by: Tolga Cakir Signed-off-by: Pali Rohár Link: https://bugzilla.kernel.org/show_bug.cgi?id=112021 Cc: stable@vger.kernel.org # v4.0+, will need backport Tested-by: Tolga Cakir Signed-off-by: Guenter Roeck --- drivers/hwmon/dell-smm-hwmon.c | 25 ++++++++++++++++++++----- 1 file changed, 20 insertions(+), 5 deletions(-) diff --git a/drivers/hwmon/dell-smm-hwmon.c b/drivers/hwmon/dell-smm-hwmon.c index 4bbc58714868..2ac87d553e22 100644 --- a/drivers/hwmon/dell-smm-hwmon.c +++ b/drivers/hwmon/dell-smm-hwmon.c @@ -238,7 +238,7 @@ static int i8k_get_fan_speed(int fan) /* * Read the fan type. */ -static int i8k_get_fan_type(int fan) +static int _i8k_get_fan_type(int fan) { struct smm_regs regs = { .eax = I8K_SMM_GET_FAN_TYPE, }; @@ -249,6 +249,17 @@ static int i8k_get_fan_type(int fan) return i8k_smm(®s) ? : regs.eax & 0xff; } +static int i8k_get_fan_type(int fan) +{ + /* I8K_SMM_GET_FAN_TYPE SMM call is expensive, so cache values */ + static int types[2] = { INT_MIN, INT_MIN }; + + if (types[fan] == INT_MIN) + types[fan] = _i8k_get_fan_type(fan); + + return types[fan]; +} + /* * Read the fan nominal rpm for specific fan speed. */ @@ -782,13 +793,17 @@ static int __init i8k_init_hwmon(void) if (err >= 0) i8k_hwmon_flags |= I8K_HWMON_HAVE_TEMP4; - /* First fan attributes, if fan type is OK */ - err = i8k_get_fan_type(0); + /* First fan attributes, if fan status or type is OK */ + err = i8k_get_fan_status(0); + if (err < 0) + err = i8k_get_fan_type(0); if (err >= 0) i8k_hwmon_flags |= I8K_HWMON_HAVE_FAN1; - /* Second fan attributes, if fan type is OK */ - err = i8k_get_fan_type(1); + /* Second fan attributes, if fan status or type is OK */ + err = i8k_get_fan_status(1); + if (err < 0) + err = i8k_get_fan_type(1); if (err >= 0) i8k_hwmon_flags |= I8K_HWMON_HAVE_FAN2; -- 2.20.1