[PATCH] i2c-i801: Fix resume when PEC is used

Fix for bug #6395:

Fail to resume on Tecra M2 with ADM1032 and Intel 82801DBM

The BIOS of the Tecra M2 doesn't like it when it has to reboot or resume
after the i2c-i801 driver has left the SMBus in PEC mode.  The most simple
fix is to clear the PEC bit after after every transaction.  That's what
this driver was doing up to 2.6.15 (inclusive).

Thanks to Daniele Gaffuri for the very good report.

Signed-off-by: Jean Delvare <khali@linux-fr.org>
Cc: Greg KH <greg@kroah.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 5 insertions, 0 deletions

diff --git a/drivers/i2c/busses/i2c-i801.c b/drivers/i2c/busses/i2c-i801.c
index 8e0f3158215f..dfca74933625 100644
--- a/drivers/i2c/busses/i2c-i801.c
+++ b/drivers/i2c/busses/i2c-i801.c
@@ -478,6 +478,11 @@ static s32 i801_access(struct i2c_adapter * adap, u16 addr,
                 ret = i801_transaction();
         }
 
+        /* Some BIOSes don't like it when PEC is enabled at reboot or resume
+           time, so we forcibly disable it after every transaction. */
+        if (hwpec)
+                outb_p(0, SMBAUXCTL);
+
         if(block)
                 return ret;
         if(ret)