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    Subject[PATCH] applesmc: Bump max wait and rearrange udelay
    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@gmail.com>

    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) {
    - 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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      Last update: 2012-09-16 01:01    [W:0.025 / U:59.948 seconds]
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