[Quantal][PATCH 1/2] hwmon: (applesmc) Shorten minimum wait time

Seth Forshee seth.forshee at canonical.com
Thu Aug 9 15:23:37 UTC 2012

From: Henrik Rydberg <rydberg at euromail.se>

The 2012 series of MacBooks have a faster SMC, and the current driver
timings do not work at all. Tests show that decreasing the minimum
wait time, from 64 us to 16 us, works well. Since this is still larger
than the original minimum of 10 us used before 2008, there is nothing
inherently problematic with changing it. The fail frequency on older
machines seems to increase slightly, but not enough to be noticeable.

Tested on MBA11, MBA31, MBA5,2, MBP9,2.

The patch was originally written by adamski99 (ubuntuforums.org) and
later tested by janhouse (bbs.archlinux.org).

Signed-off-by: Henrik Rydberg <rydberg at euromail.se>
Signed-off-by: Guenter Roeck <linux at roeck-us.net>
(cherry picked from commit a332bf9a65ab34b01226ed177f6937af843c8465)
BugLink: http://bugs.launchpad.net/bugs/1034449
Signed-off-by: Seth Forshee <seth.forshee at canonical.com>
 drivers/hwmon/applesmc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 2cde9ec..745bd41 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -54,7 +54,7 @@
 /* wait up to 32 ms for a status change. */
-#define APPLESMC_MIN_WAIT	0x0040
+#define APPLESMC_MIN_WAIT	0x0010
 #define APPLESMC_MAX_WAIT	0x8000

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