linux-kernel - [RFC PATCH 6/8] i2c-octeon: Flush TWSI writes with readback

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Message-Id: <a3fe08c015f2700f5cdd6b2b770d3e1254751b5e.1455782324.git.jglauber@cavium.com>
Date:	Thu, 18 Feb 2016 09:22:28 +0100
From:	Jan Glauber <jglauber@...ium.com>
To:	linux-i2c@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, Wolfram Sang <wsa@...-dreams.de>,
	Peter Swain <pswain@...ium.com>,
	Jan Glauber <jglauber@...ium.com>
Subject: [RFC PATCH 6/8] i2c-octeon: Flush TWSI writes with readback

From: Peter Swain <pswain@...ium.com>

Signed-off-by: Peter Swain <pswain@...ium.com>
Signed-off-by: Jan Glauber <jglauber@...ium.com>
Acked-by: David Daney <ddaney@...iumnetworks.com>
---
 drivers/i2c/busses/i2c-octeon.c | 19 ++++++++++++-------
 1 file changed, 12 insertions(+), 7 deletions(-)

diff --git a/drivers/i2c/busses/i2c-octeon.c b/drivers/i2c/busses/i2c-octeon.c
index 0b28d8c..bb15a9c 100644
--- a/drivers/i2c/busses/i2c-octeon.c
+++ b/drivers/i2c/busses/i2c-octeon.c
@@ -130,6 +130,12 @@ static int timeout = 2;
 module_param(timeout, int, 0444);
 MODULE_PARM_DESC(timeout, "Low-level device timeout (ms)");
 
+static void writeqflush(u64 val, void __iomem *addr)
+{
+	__raw_writeq(val, addr);
+	__raw_readq(addr);	/* wait for write to land */
+}
+
 /**
  * octeon_i2c_write_sw - write an I2C core register
  * @i2c: The struct octeon_i2c
@@ -190,8 +196,7 @@ static u8 octeon_i2c_read_sw(struct octeon_i2c *i2c, u64 eop_reg)
  */
 static void octeon_i2c_write_int(struct octeon_i2c *i2c, u64 data)
 {
-	__raw_writeq(data, i2c->twsi_base + TWSI_INT);
-	__raw_readq(i2c->twsi_base + TWSI_INT);
+	writeqflush(data, i2c->twsi_base + TWSI_INT);
 }
 
 /**
@@ -797,10 +802,10 @@ static int octeon_i2c_simple_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
 
 		for (i = 0; i < msgs[0].len - 4 && i < 4; i++, j--)
 			ext |= (u64) msgs[0].buf[j] << (8 * i);
-		__raw_writeq(ext, i2c->twsi_base + SW_TWSI_EXT);
+		writeqflush(ext, i2c->twsi_base + SW_TWSI_EXT);
 	}
 
-	__raw_writeq(cmd, i2c->twsi_base + SW_TWSI);
+	writeqflush(cmd, i2c->twsi_base + SW_TWSI);
 
 	ret = octeon_i2c_hlc_wait(i2c);
 	if (ret)
@@ -846,7 +851,7 @@ static int octeon_i2c_ia_read(struct octeon_i2c *i2c, struct i2c_msg *msgs)
 		cmd |= (u64) msgs[0].buf[0] << SW_TWSI_IA_SHIFT;
 
 	octeon_i2c_hlc_int_clear(i2c);
-	__raw_writeq(cmd, i2c->twsi_base + SW_TWSI);
+	writeqflush(cmd, i2c->twsi_base + SW_TWSI);
 
 	ret = octeon_i2c_hlc_wait(i2c);
 	if (ret)
@@ -906,10 +911,10 @@ static int octeon_i2c_ia_write(struct octeon_i2c *i2c, struct i2c_msg *msgs)
 		set_ext = true;
 	}
 	if (set_ext)
-		__raw_writeq(ext, i2c->twsi_base + SW_TWSI_EXT);
+		writeqflush(ext, i2c->twsi_base + SW_TWSI_EXT);
 
 	octeon_i2c_hlc_int_clear(i2c);
-	__raw_writeq(cmd, i2c->twsi_base + SW_TWSI);
+	writeqflush(cmd, i2c->twsi_base + SW_TWSI);
 
 	ret = octeon_i2c_hlc_wait(i2c);
 	if (ret)
-- 
1.9.1