linux-kernel - [PATCH] i2c-designware: Manually set RESTART bit between messages

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Date:	Fri, 21 Jun 2013 15:05:28 +0800
From:	Chew Chiau Ee <chiaue.ee.chew@...el.com>
To:	Wolfram Sang <wsa@...-dreams.de>
Cc:	linux-i2c@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH] i2c-designware: Manually set RESTART bit between messages

From: Chew, Chiau Ee <chiau.ee.chew@...el.com>

If both IC_EMPTYFIFO_HOLD_MASTER_EN and IC_RESTART_EN are set to 1, the
Designware I2C controller doesn't generate RESTART unless user specifically
requests it by setting RESTART bit in IC_DATA_CMD register.

Since IC_EMPTYFIFO_HOLD_MASTER_EN setting can't be detected from hardware
register, we must always manually set the restart bit between messages.

Signed-off-by: Chew, Chiau Ee <chiau.ee.chew@...el.com>
---
 drivers/i2c/busses/i2c-designware-core.c |   14 ++++++++++++++
 1 files changed, 14 insertions(+), 0 deletions(-)

diff --git a/drivers/i2c/busses/i2c-designware-core.c b/drivers/i2c/busses/i2c-designware-core.c
index 3de5494..9348439 100644
--- a/drivers/i2c/busses/i2c-designware-core.c
+++ b/drivers/i2c/busses/i2c-designware-core.c
@@ -403,6 +403,7 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 	u32 addr = msgs[dev->msg_write_idx].addr;
 	u32 buf_len = dev->tx_buf_len;
 	u8 *buf = dev->tx_buf;
+	bool need_restart = false;
 
 	intr_mask = DW_IC_INTR_DEFAULT_MASK;
 
@@ -430,6 +431,14 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 			/* new i2c_msg */
 			buf = msgs[dev->msg_write_idx].buf;
 			buf_len = msgs[dev->msg_write_idx].len;
+
+			/* If both IC_EMPTYFIFO_HOLD_MASTER_EN and
+			 * IC_RESTART_EN are set, we must manually
+			 * set restart bit between messages.
+			 */
+			if ((dev->master_cfg & DW_IC_CON_RESTART_EN) &&
+					(dev->msg_write_idx > 0))
+				need_restart = true;
 		}
 
 		tx_limit = dev->tx_fifo_depth - dw_readl(dev, DW_IC_TXFLR);
@@ -448,6 +457,11 @@ i2c_dw_xfer_msg(struct dw_i2c_dev *dev)
 			    buf_len == 1)
 				cmd |= BIT(9);
 
+			if (need_restart) {
+				cmd |= BIT(10);
+				need_restart = false;
+			}
+
 			if (msgs[dev->msg_write_idx].flags & I2C_M_RD) {
 
 				/* avoid rx buffer overrun */
-- 
1.7.4.4

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