On Sat, 15 Sep 2012, Parag Warudkar wrote:
>
>
> On Sat, 15 Sep 2012, Guenter Roeck wrote:
> >
> > Also, since the delay time can get quite large, would it make sense to replace
> > udelay with usleep_range() ?
> >
>
> Yes, I think that would be a good thing to do. We could sleep in range of
> us<<=1 and us<<1 and if usleep_range() returns actual sleep time we can
> factor that in for next loop iteration if necessary. Gotta think a bit on
> that one.
>
> I will rework the patch to fix the loop termination and keep the bump to
> 0x10000 in place and possibly also experiment with usleep_range().
>
Below is what I am experimenting with right now. I chose to keep the
APPLESMC_MAX_WAIT to current 0x8000 (32ms). With the fixed loop
termination and use of usleep_range() instead of udelay - I will try to
run this a couple days and see if I can recreate the failure within 32ms.
Does this look ok? (I haven't yet changed send_byte to use usleep_range -
if this approach looks ok I can change that as well.)
Signed-off-by: Parag Warudkar <parag.lkml@xxxxxxxxx>
diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
index 2827088..6610037 100644
--- a/drivers/hwmon/applesmc.c
+++ b/drivers/hwmon/applesmc.c
@@ -168,15 +168,20 @@ static struct workqueue_struct *applesmc_led_wq;
static int wait_read(void)
{
u8 status;
- int us;
- for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) {
- udelay(us);
+ unsigned long r1_us = APPLESMC_MIN_WAIT;
+ unsigned long r2_us;
+ do {
status = inb(APPLESMC_CMD_PORT);
/* read: wait for smc to settle */
if (status & 0x01)
return 0;
- }
-
+ r2_us = r1_us << 2;
+ if (r2_us > APPLESMC_MAX_WAIT)
+ goto fail;
+ usleep_range(r1_us, r2_us);
+ r1_us = r2_us;
+ } while (1);
+fail:
pr_warn("wait_read() fail: 0x%02x\n", status);
return -EIO;
}
@@ -191,12 +196,13 @@ static int send_byte(u8 cmd, u16 port)
int us;
outb(cmd, port);
- for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) {
- udelay(us);
+ for (us = APPLESMC_MIN_WAIT; us <= APPLESMC_MAX_WAIT; us <<= 1) {
status = inb(APPLESMC_CMD_PORT);
/* write: wait for smc to settle */
- if (status & 0x02)
+ if (status & 0x02) {
+ udelay(us);
continue;
+ }
/* ready: cmd accepted, return */
if (status & 0x04)
return 0;
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