On Tue, Oct 01, 2013 at 12:55:26PM +0200, Henrik Rydberg wrote:
> > >Warning message triggered with 3.12.0-0.rc3.git0.1.fc21.x86_64.
> > >
> > >[ 10.886016] applesmc: key count changed from 261 to 1174405121
> > >
> >
> > Explains the crash, but the new key count is very wrong. 1174405121 =
> > 0x46000001.
> > Which I guess explains the subsequent memory allocation error in the log.
> >
> > Henrik, any idea what might be going on ? Is it possible that the previous
> > command failure leaves some state machine in a bad state ?
>
> I seem to recall a report on another similar state problem on newer
> machines, so maybe, yes. Older machines seem fine, I have never
> encountered the problem myself. Here is a patch to test that
> theory. It has been tested to be pretty harmless on two different
> generations.
>
> I really really do not want to add an 'if (value is insane)' check ;-)
>
Chris,
any chance you can load this patch on an affected machine so we can get
test feedback ? This one is too experimental to submit upstream without
knowing that it really fixes the problem.
Thanks,
Guenter
> Thanks,
> Henrik
>
> From d48a9e4e6e45dcd9c7e7ad88df714b92772a62d6 Mon Sep 17 00:00:00 2001
> From: Henrik Rydberg <rydb...@euromail.se>
> Date: Tue, 1 Oct 2013 12:16:09 +0200
> Subject: [PATCH] applesmc remedy take 1
>
> Conjectured problem: there are remnant bytes ready on the data line
> which corrupts the read after a failure.
>
> Remedy: assuming bit0 is the read valid line, try to flush it before
> starting a new command.
>
> Exception: the write-number-of-bytes-to-read command seems to differ
> between models (it may not be needed on the newest), so do not try to
> flush the data at that particular point.
>
> Tested on a MacBookPro10,1 and a MacBookAir3,1, but the original problem
> has not been reproduced, so the actual effect of this patch is unknown.
> ---
> drivers/hwmon/applesmc.c | 29 +++++++++++++++++++++--------
> 1 file changed, 21 insertions(+), 8 deletions(-)
>
> diff --git a/drivers/hwmon/applesmc.c b/drivers/hwmon/applesmc.c
> index 98814d1..f6eaf6d1 100644
> --- a/drivers/hwmon/applesmc.c
> +++ b/drivers/hwmon/applesmc.c
> @@ -186,10 +186,23 @@ static int wait_read(void)
> * send_byte - Write to SMC port, retrying when necessary. Callers
> * must hold applesmc_lock.
> */
> -static int send_byte(u8 cmd, u16 port)
> +static int send_byte(u8 cmd, u16 port, bool flush)
> {
> - u8 status;
> - int us;
> + u8 status, data;
> + int us, nskip;
> +
> + if (flush) {
> + /* read the data port until bit0 is cleared */
> + for (nskip = 0; nskip < 16; nskip++) {
> + udelay(APPLESMC_MIN_WAIT);
> + status = inb(APPLESMC_CMD_PORT);
> + if (!(status & 0x01))
> + break;
> + data = inb(APPLESMC_DATA_PORT);
> + }
> + if (nskip)
> + pr_warn("flushed %d bytes\n", nskip);
> + }
>
> outb(cmd, port);
> for (us = APPLESMC_MIN_WAIT; us < APPLESMC_MAX_WAIT; us <<= 1) {
> @@ -215,7 +228,7 @@ static int send_byte(u8 cmd, u16 port)
>
> static int send_command(u8 cmd)
> {
> - return send_byte(cmd, APPLESMC_CMD_PORT);
> + return send_byte(cmd, APPLESMC_CMD_PORT, true);
> }
>
> static int send_argument(const char *key)
> @@ -223,7 +236,7 @@ static int send_argument(const char *key)
> int i;
>
> for (i = 0; i < 4; i++)
> - if (send_byte(key[i], APPLESMC_DATA_PORT))
> + if (send_byte(key[i], APPLESMC_DATA_PORT, true))
> return -EIO;
> return 0;
> }
> @@ -237,7 +250,7 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer,
> u8 len)
> return -EIO;
> }
>
> - if (send_byte(len, APPLESMC_DATA_PORT)) {
> + if (send_byte(len, APPLESMC_DATA_PORT, false)) {
> pr_warn("%.4s: read len fail\n", key);
> return -EIO;
> }
> @@ -262,13 +275,13 @@ static int write_smc(u8 cmd, const char *key, const u8
> *buffer, u8 len)
> return -EIO;
> }
>
> - if (send_byte(len, APPLESMC_DATA_PORT)) {
> + if (send_byte(len, APPLESMC_DATA_PORT, true)) {
> pr_warn("%.4s: write len fail\n", key);
> return -EIO;
> }
>
> for (i = 0; i < len; i++) {
> - if (send_byte(buffer[i], APPLESMC_DATA_PORT)) {
> + if (send_byte(buffer[i], APPLESMC_DATA_PORT, true)) {
> pr_warn("%s: write data fail\n", key);
> return -EIO;
> }
> --
> 1.8.3.4
>
>
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