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[PATCH 3.19.y-ckt 131/164] i2c: img-scb: Clear line and interrupt status before starting a transfer

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  [PATCH 3.19.y-ckt 131/164] i2c: img-scb: Clear line and interrupt status before starting a transfer Kamal Mostafa <kamal@canonical.com> - 2015-12-02 18:20 +0100

#1282087 — [PATCH 3.19.y-ckt 131/164] i2c: img-scb: Clear line and interrupt status before starting a transfer

3.19.8-ckt11 -stable review patch.  If anyone has any objections, please let me know.

------------------

From: Sifan Naeem <sifan.naeem@imgtec.com>

commit 1ed6faedfc9741cca2d97b25ab73902ba7177093 upstream.

Clear line status and all generated interrupts from the interrupt
status register before starting a transfer, as we may have
unserviced interrupts from previous transfers that might be
handled in the context of the new transfer.

Fixes: commit 27bce457d588 ("i2c: img-scb: Add Imagination Technologies I2C SCB driver")
Signed-off-by: Sifan Naeem <sifan.naeem@imgtec.com>
Acked-by: James Hogan <james.hogan@imgtec.com>
Reviewed-by: James Hartley <james.hartley@imgtec.com>
Signed-off-by: Wolfram Sang <wsa@the-dreams.de>
Signed-off-by: Kamal Mostafa <kamal@canonical.com>
---
 drivers/i2c/busses/i2c-img-scb.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/drivers/i2c/busses/i2c-img-scb.c b/drivers/i2c/busses/i2c-img-scb.c
index 515cbb4..90ffb07 100644
--- a/drivers/i2c/busses/i2c-img-scb.c
+++ b/drivers/i2c/busses/i2c-img-scb.c
@@ -1058,6 +1058,15 @@ static int img_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 		i2c->last_msg = (i == num - 1);
 		reinit_completion(&i2c->msg_complete);
 
+		/*
+		 * Clear line status and all interrupts before starting a
+		 * transfer, as we may have unserviced interrupts from
+		 * previous transfers that might be handled in the context
+		 * of the new transfer.
+		 */
+		img_i2c_writel(i2c, SCB_INT_CLEAR_REG, ~0);
+		img_i2c_writel(i2c, SCB_CLEAR_REG, ~0);
+
 		if (atomic)
 			img_i2c_atomic_start(i2c);
 		else if (msg->flags & I2C_M_RD)
-- 
1.9.1

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