Piteball/android_kernel_google_msm
1
0
Fork 0
mirror of https://github.com/followmsi/android_kernel_google_msm.git synced 2024-11-06 23:17:41 +00:00
Code Issues Projects Releases Wiki Activity

hwmon: (applesmc) Always read until end of data

Browse source 
commit 25f2bd7f5a upstream.

The crash reported and investigated in commit 5f4513 turned out to be
caused by a change to the read interface on newer (2012) SMCs.

Tests by Chris show that simply reading the data valid line is enough
for the problem to go away. Additional tests show that the newer SMCs
no longer wait for the number of requested bytes, but start sending
data right away.  Apparently the number of bytes to read is no longer
specified as before, but instead found out by reading until end of
data. Failure to read until end of data confuses the state machine,
which eventually causes the crash.

As a remedy, assuming bit0 is the read valid line, make sure there is
nothing more to read before leaving the read function.

Tested to resolve the original problem, and runtested on MBA3,1,
MBP4,1, MBP8,2, MBP10,1, MBP10,2. The patch seems to have no effect on
machines before 2012.

Tested-by: Chris Murphy <chris@cmurf.com>
Signed-off-by: Henrik Rydberg <rydberg@euromail.se>
Signed-off-by: Guenter Roeck <linux@roeck-us.net>
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
Cc: Qiang Huang <h.huangqiang@huawei.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Henrik Rydberg 2013-10-02 19:15:03 +02:00 committed by Greg Kroah-Hartman
parent 7aa8c17047
commit e4b2585a85
1 changed files with 13 additions and 0 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

13
drivers/hwmon/applesmc.c
View file

@ -212,6 +212,7 @@ static int send_argument(const char *key)
static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
{
u8 status, data = 0;
int i;
if (send_command(cmd) || send_argument(key)) {
@ -219,6 +220,7 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
return -EIO;
}
/* This has no effect on newer (2012) SMCs */
outb(len, APPLESMC_DATA_PORT);
for (i = 0; i < len; i++) {
@ -229,6 +231,17 @@ static int read_smc(u8 cmd, const char *key, u8 *buffer, u8 len)
buffer[i] = inb(APPLESMC_DATA_PORT);
}
/* Read the data port until bit0 is cleared */
for (i = 0; i < 16; i++) {
udelay(APPLESMC_MIN_WAIT);
status = inb(APPLESMC_CMD_PORT);
if (!(status & 0x01))
break;
data = inb(APPLESMC_DATA_PORT);
}
if (i)
pr_warn("flushed %d bytes, last value is: %d\n", i, data);
return 0;
}