> >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 ;-)
Thanks,
Henrik
>From d48a9e4e6e45dcd9c7e7ad88df714b92772a62d6 Mon Sep 17 00:00:00 2001
From: Henrik Rydberg <rydberg@xxxxxxxxxxx>
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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