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

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Submitter Seth Forshee
Date Aug. 9, 2012, 3:23 p.m.
Message ID <1344525818-27653-2-git-send-email-seth.forshee@canonical.com>
Download mbox | patch
Permalink /patch/176176/
State New
Headers show

Comments

Seth Forshee - Aug. 9, 2012, 3:23 p.m.
From: Henrik Rydberg <rydberg@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@euromail.se>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
(cherry picked from commit a332bf9a65ab34b01226ed177f6937af843c8465)
BugLink: http://bugs.launchpad.net/bugs/1034449
Signed-off-by: Seth Forshee <seth.forshee@canonical.com>
---
 drivers/hwmon/applesmc.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Patch

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 @@ 
 #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