linux-kernel - [PATCH] i2c: davinci: Add block read functionality for IPMI

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Message-ID: <1398970186-12204-1-git-send-email-m-karicheri2@ti.com>
Date:	Thu, 1 May 2014 14:49:46 -0400
From:	Murali Karicheri <m-karicheri2@...com>
To:	<davinci-linux-open-source@...ux.davincidsp.com>,
	<linux-i2c@...r.kernel.org>, <linux-kernel@...r.kernel.org>
CC:	Murali Karicheri <m-karicheri2@...com>,
	Garrett Ding <g-ding@...com>, Sekhar Nori <nsekhar@...com>,
	Kevin Hilman <khilman@...prootsystems.com>,
	Wolfram Sang <wsa@...-dreams.de>,
	Santosh Shilimkar <santosh.shilimkar@...com>
Subject: [PATCH] i2c: davinci: Add block read functionality for IPMI

Intelligent Plaform Management Interface (IPMI) requires I2C driver
to support block read, where the first byte received from slave is
the length of following data:-
 Added length check if the read type is block read (I2C_M_RECV_LEN)
 Send NACK/STOP bits before last byte is received

Signed-off-by: Garrett Ding <g-ding@...com>
Signed-off-by: Murali Karicheri <m-karicheri2@...com>
Tested-by: Garrett Ding <g-ding@...com>
CC: Sekhar Nori <nsekhar@...com>
CC: Kevin Hilman <khilman@...prootsystems.com>
CC: Wolfram Sang <wsa@...-dreams.de>
CC: Santosh Shilimkar <santosh.shilimkar@...com>
---
 Tested on a customer board based on K2HK SoC
 drivers/i2c/busses/i2c-davinci.c |   42 +++++++++++++++++++++++++++++++++-----
 1 file changed, 37 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-davinci.c b/drivers/i2c/busses/i2c-davinci.c
index 389bc68..cd97920 100644
--- a/drivers/i2c/busses/i2c-davinci.c
+++ b/drivers/i2c/busses/i2c-davinci.c
@@ -97,6 +97,10 @@
 #define DAVINCI_I2C_IMR_NACK	BIT(1)
 #define DAVINCI_I2C_IMR_AL	BIT(0)
 
+/* capabilities */
+#define I2C_CAPABILITIES	(I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL | \
+				 I2C_FUNC_SMBUS_READ_BLOCK_DATA)
+
 struct davinci_i2c_dev {
 	struct device           *dev;
 	void __iomem		*base;
@@ -318,7 +322,13 @@ i2c_davinci_xfer_msg(struct i2c_adapter *adap, struct i2c_msg *msg, int stop)
 	davinci_i2c_write_reg(dev, DAVINCI_I2C_SAR_REG, msg->addr);
 
 	dev->buf = msg->buf;
-	dev->buf_len = msg->len;
+
+	 /* if first received byte is length, set buf_len = 0xffff as flag */
+	if (msg->flags & I2C_M_RECV_LEN)
+		dev->buf_len = 0xffff;
+	else
+		dev->buf_len = msg->len;
+
 	dev->stop = stop;
 
 	davinci_i2c_write_reg(dev, DAVINCI_I2C_CNT_REG, dev->buf_len);
@@ -456,7 +466,7 @@ i2c_davinci_xfer(struct i2c_adapter *adap, struct i2c_msg msgs[], int num)
 
 static u32 i2c_davinci_func(struct i2c_adapter *adap)
 {
-	return I2C_FUNC_I2C | I2C_FUNC_SMBUS_EMUL;
+	return I2C_CAPABILITIES;
 }
 
 static void terminate_read(struct davinci_i2c_dev *dev)
@@ -528,10 +538,32 @@ static irqreturn_t i2c_davinci_isr(int this_irq, void *dev_id)
 
 		case DAVINCI_I2C_IVR_RDR:
 			if (dev->buf_len) {
-				*dev->buf++ =
-				    davinci_i2c_read_reg(dev,
-							 DAVINCI_I2C_DRR_REG);
+				*dev->buf++ = davinci_i2c_read_reg(dev,
+							DAVINCI_I2C_DRR_REG);
+				/*
+				 * check if the first received byte is message
+				 * length, i.e, I2C_M_RECV_LEN
+				 */
+				if (dev->buf_len == 0xffff)
+					dev->buf_len = *(dev->buf - 1) + 1;
+
 				dev->buf_len--;
+				/*
+				 * send NACK/STOP bits BEFORE last byte is
+				 * received
+				 */
+				if (dev->buf_len == 1) {
+					w = davinci_i2c_read_reg(dev,
+							DAVINCI_I2C_MDR_REG);
+					w |= DAVINCI_I2C_MDR_NACK;
+					davinci_i2c_write_reg(dev,
+							DAVINCI_I2C_MDR_REG, w);
+
+					w |= DAVINCI_I2C_MDR_STP;
+					davinci_i2c_write_reg(dev,
+							DAVINCI_I2C_MDR_REG, w);
+				}
+
 				if (dev->buf_len)
 					continue;
 
-- 
1.7.9.5

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