On Sat, Sep 15, 2012 at 06:42:30PM -0400, Parag Warudkar wrote:
> I have been getting a steady stream of wait_read timeouts on my 2010 MBP.
>
> After playing around with various values of APPLESMC_MAX_WAIT a value of
> 0x10000 reduces the wait_read failures to zero under most normal workloads
> - with and without AC power plugged in, at idle and and at make -j4 loads.
>
> While there I noticed we don't really need to udelay before first inb() -
> so I moved it down to after first and subsequent failures.
>
> Been running this for couple days without any issues.
>
> Signed-off-by: Parag Warudkar <parag.lkml@xxxxxxxxx>
>
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index 2827088..46cb458 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
> @@ -56,7 +56,7 @@
> /* wait up to 32 ms for a status change. */
> #define APPLESMC_MIN_WAIT 0x0010
> #define APPLESMC_RETRY_WAIT 0x0100
> -#define APPLESMC_MAX_WAIT 0x8000
> +#define APPLESMC_MAX_WAIT 0x10000
>
> #define APPLESMC_READ_CMD 0x10
> #define APPLESMC_WRITE_CMD 0x11
> @@ -170,11 +170,11 @@ static int wait_read(void)
> u8 status;
> int us;
> for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) {
I wonder if it would make sense to keep APPLESMC_MAX_WAIT as it is now
and replace the loop termination conditions with
us <= APPLESMC_MAX_WAIT
That would accomplish the same, and APPLESMC_MAX_WAIT would reflect
the real maximum wait time.
Also, since the delay time can get quite large, would it make sense to replace
udelay with usleep_range() ?
Guenter
> - udelay(us);
> status = inb(APPLESMC_CMD_PORT);
> /* read: wait for smc to settle */
> if (status & 0x01)
> return 0;
> + udelay(us);
> }
>
> pr_warn("wait_read() fail: 0x%02x\n", status);
> @@ -192,11 +192,12 @@ static int send_byte(u8 cmd, u16 port)
>
> outb(cmd, port);
> for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) {
> - udelay(us);
> 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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