Patchwork [1/2] i2c-designware: always clear interrupts before enabling them

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Submitter Mika Westerberg
Date May 13, 2013, 10:54 a.m.
Message ID <1368442471-7582-1-git-send-email-mika.westerberg@linux.intel.com>
Download mbox | patch
Permalink /patch/243358/
State Accepted
Headers show

Comments

Mika Westerberg - May 13, 2013, 10:54 a.m.
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@linux.intel.com>
---
 drivers/i2c/busses/i2c-designware-core.c |    3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)
Wolfram Sang - May 17, 2013, 8:31 a.m.
On Mon, May 13, 2013 at 01:54:30PM +0300, Mika Westerberg wrote:
> 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@linux.intel.com>

Applied to for-current, thanks! Added stable, too.

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Patch

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 21fbb34..7a89ca5 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -383,7 +383,8 @@  static void i2c_dw_xfer_init(struct dw_i2c_dev *dev)
 	/* Enable the adapter */
 	__i2c_dw_enable(dev, true);
 
-	/* Enable interrupts */
+	/* Clear and enable interrupts */
+	i2c_dw_clear_int(dev);
 	dw_writel(dev, DW_IC_INTR_DEFAULT_MASK, DW_IC_INTR_MASK);
 }