diff options
| author | Henrik Rydberg <rydberg@euromail.se> | 2008-10-18 20:27:43 -0700 |
|---|---|---|
| committer | Linus Torvalds <torvalds@linux-foundation.org> | 2008-10-20 08:52:35 -0700 |
| commit | 8c9398d1e9766e3659e277acb2e8ca1c17684139 (patch) | |
| tree | 160520c76c2dfbe89398b6c53aa8813e212abed3 /drivers/hwmon | |
| parent | 07e8dbd3ebbdedc71335049dd4b0d542cb038d7d (diff) | |
| download | linux-8c9398d1e9766e3659e277acb2e8ca1c17684139.tar.gz linux-8c9398d1e9766e3659e277acb2e8ca1c17684139.tar.bz2 linux-8c9398d1e9766e3659e277acb2e8ca1c17684139.zip | |
hwmon: applesmc: lighter wait mechanism, drastic improvement
The read fail ratio is sensitive to the delay between the first byte
written and the first byte read; apparently the sensors cannot be rushed.
Increasing the minimum wait time, without changing the total wait time,
improves the fail ratio from a 8% chance that any of the sensors fails in
one read, down to 0.4%, on a Macbook Air. On a Macbook Pro 3,1, the
effect is even more apparent. By reducing the number of status polls, the
ratio is further improved to below 0.1%. Finally, increasing the total
wait time brings the fail ratio down to virtually zero.
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Tested-by: Bob McElrath <bob@mcelrath.org>
Cc: Nicolas Boichat <nicolas@boichat.ch>
Cc: "Mark M. Hoffman" <mhoffman@lightlink.com>
Cc: Jean Delvare <khali@linux-fr.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'drivers/hwmon')
| -rw-r--r-- | drivers/hwmon/applesmc.c | 22 |
1 files changed, 12 insertions, 10 deletions
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c index 59266ce60cc2..bc011da79e14 100644 --- a/drivers/hwmon/applesmc.c +++ b/drivers/hwmon/applesmc.c @@ -49,6 +49,9 @@ #define APPLESMC_MAX_DATA_LENGTH 32 +#define APPLESMC_MIN_WAIT 0x0040 +#define APPLESMC_MAX_WAIT 0x8000 + #define APPLESMC_STATUS_MASK 0x0f #define APPLESMC_READ_CMD 0x10 #define APPLESMC_WRITE_CMD 0x11 @@ -172,25 +175,25 @@ static unsigned int key_at_index; static struct workqueue_struct *applesmc_led_wq; /* - * __wait_status - Wait up to 10ms for the status port to get a certain value + * __wait_status - Wait up to 32ms for the status port to get a certain value * (masked with 0x0f), returning zero if the value is obtained. Callers must * hold applesmc_lock. */ static int __wait_status(u8 val) { - unsigned int i; + int us; val = val & APPLESMC_STATUS_MASK; - for (i = 0; i < 1000; i++) { + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { + udelay(us); if ((inb(APPLESMC_CMD_PORT) & APPLESMC_STATUS_MASK) == val) { if (debug) printk(KERN_DEBUG - "Waited %d us for status %x\n", - i*10, val); + "Waited %d us for status %x\n", + 2 * us - APPLESMC_MIN_WAIT, val); return 0; } - udelay(10); } printk(KERN_WARNING "applesmc: wait status failed: %x != %x\n", @@ -206,13 +209,12 @@ static int __wait_status(u8 val) */ static int send_command(u8 cmd) { - int i; - for (i = 0; i < 1000; i++) { + int us; + for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) { outb(cmd, APPLESMC_CMD_PORT); - udelay(5); + udelay(us); if ((inb(APPLESMC_CMD_PORT) & APPLESMC_STATUS_MASK) == 0x0c) return 0; - udelay(5); } printk(KERN_WARNING "applesmc: command failed: %x -> %x\n", cmd, inb(APPLESMC_CMD_PORT)); |