hwmon: (applesmc) Shorten minimum wait time

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@euromail.se>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>

diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 0162f55278057796cf52674c2282631f4852cb43..f41585ecbe2b931988f88a0609734a0593aecf51 100644 (file)
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -54,7 +54,7 @@
 #define APPLESMC_MAX_DATA_LENGTH 32
 
 /* wait up to 32 ms for a status change. */
-#define APPLESMC_MIN_WAIT      0x0040
+#define APPLESMC_MIN_WAIT      0x0010
 #define APPLESMC_MAX_WAIT      0x8000
 
 #define APPLESMC_STATUS_MASK   0x0f