linux-kernel - [PATCH v3 4/4] i2c: omap: add notes related to i2c multimaster mode

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Message-Id: <1416685634-5864-5-git-send-email-al.kochet@gmail.com>
Date:	Sat, 22 Nov 2014 23:47:14 +0400
From:	Alexander Kochetkov <al.kochet@...il.com>
To:	linux-omap@...r.kernel.org, linux-i2c@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc:	Wolfram Sang <wsa@...-dreams.de>, Tony Lindgren <tony@...mide.com>,
	Felipe Balbi <balbi@...com>, al.kochet@...il.com
Subject: [PATCH v3 4/4] i2c: omap: add notes related to i2c multimaster mode

No functional changes.

Signed-off-by: Alexander Kochetkov <al.kochet@...il.com>
Reviewed-by: Felipe Balbi <balbi@...com>
---
 drivers/i2c/busses/i2c-omap.c |   12 +++++++++++-
 1 file changed, 11 insertions(+), 1 deletion(-)

diff --git a/drivers/i2c/busses/i2c-omap.c b/drivers/i2c/busses/i2c-omap.c
index e67b7d0..f276c0c 100644
--- a/drivers/i2c/busses/i2c-omap.c
+++ b/drivers/i2c/busses/i2c-omap.c
@@ -300,6 +300,12 @@ static void __omap_i2c_init(struct omap_i2c_dev *dev)
 	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, OMAP_I2C_CON_EN);
 
 	/*
+	 * NOTE: right after setting CON_EN, STAT_BB could be 0 while the
+	 * bus is busy. It will be changed to 1 on the next IP FCLK clock.
+	 * udelay(1) will be enough to fix that.
+	 */
+
+	/*
 	 * Don't write to this register if the IE state is 0 as it can
 	 * cause deadlock.
 	 */
@@ -660,7 +666,11 @@ static int omap_i2c_xfer_msg(struct i2c_adapter *adap,
 
 	if (!dev->b_hw && stop)
 		w |= OMAP_I2C_CON_STP;
-
+	/*
+	 * NOTE: STAT_BB bit could became 1 here if another master occupy
+	 * the bus. IP successfully complete transfer when the bus will be
+	 * free again (BB reset to 0).
+	 */
 	omap_i2c_write_reg(dev, OMAP_I2C_CON_REG, w);
 
 	/*
-- 
1.7.9.5

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