[ 3.8.y.z extended stable ] Patch "i2c: designware: always clear interrupts before enabling them" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    i2c: designware: always clear interrupts before enabling them

to the linux-3.8.y-queue branch of the 3.8.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.8.y-queue

This patch is scheduled to be released in version 3.8.13.2.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.8.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 6c80835db657fbb5fc17eb6521be1d9f5807b4ac Mon Sep 17 00:00:00 2001
From: Mika Westerberg <mika.westerberg at linux.intel.com>
Date: Mon, 13 May 2013 00:54:30 +0000
Subject: i2c: designware: always clear interrupts before enabling them

commit 2a2d95e9d6d29e726cc294b65391917ed2e32bf4 upstream.

If the I2C bus is put to a low power state by an ACPI method it might pull
the SDA line low (as its power is removed). Once the bus is put to full
power state again, the SDA line is pulled back to high. This transition
looks like a STOP condition from the controller point-of-view which sets
STOP detected bit in its status register causing the driver to fail
subsequent transfers.

Fix this by always clearing all interrupts before we start a transfer.

Signed-off-by: Mika Westerberg <mika.westerberg at linux.intel.com>
Signed-off-by: Wolfram Sang <wsa at the-dreams.de>
[ kamal: backport to 3.8 ]
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/i2c/busses/i2c-designware-core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 9a6aad8..bf8ce32 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -361,7 +361,8 @@ static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
 	/* Enable the adapter */
 	dw_writel(dev, 1, DW_IC_ENABLE);

-	/* Enable interrupts */
+	/* Clear and enable interrupts */
+	i2c_dw_clear_int(dev);
 	dw_writel(dev, DW_IC_INTR_DEFAULT_MASK, DW_IC_INTR_MASK);
 }

--
1.8.1.2