linux-kernel - [PATCH 4.2.y-ckt 131/211] i2c: img-scb: Clear line and interrupt status before starting a transfer

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Message-Id: <1452023119-25647-132-git-send-email-kamal@canonical.com>
Date:	Tue,  5 Jan 2016 11:43:59 -0800
From:	Kamal Mostafa <kamal@...onical.com>
To:	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	kernel-team@...ts.ubuntu.com
Cc:	Sifan Naeem <sifan.naeem@...tec.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 4.2.y-ckt 131/211] i2c: img-scb: Clear line and interrupt status before starting a transfer

4.2.8-ckt1 -stable review patch.  If anyone has any objections, please let me know.

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

From: Sifan Naeem <sifan.naeem@...tec.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@...tec.com>
Acked-by: James Hogan <james.hogan@...tec.com>
Reviewed-by: James Hartley <james.hartley@...tec.com>
Signed-off-by: Wolfram Sang <wsa@...-dreams.de>
Signed-off-by: Kamal Mostafa <kamal@...onical.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 e4daebc..b14eeae 100644
--- a/drivers/i2c/busses/i2c-img-scb.c
+++ b/drivers/i2c/busses/i2c-img-scb.c
@@ -1060,6 +1060,15 @@ 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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