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From:   Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
To:     Wolfram Sang <wsa@the-dreams.de>, Rob Herring <robh+dt@kernel.org>,
        Mark Rutland <mark.rutland@arm.com>
Cc:     linux-i2c@vger.kernel.org, bcm-kernel-feedback-list@broadcom.com,
        Ray Jui <ray.jui@broadcom.com>,
        Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>,
        linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org,
        Michael Cheng <ccheng@broadcom.com>,
        Srinath Mannam <srinath.mannam@broadcom.com>
Subject: [PATCH 1/1] i2c: iproc: Add multi byte read-write support for slave mode
Date:   Thu,  9 May 2019 09:35:17 +0530
Message-Id: <1557374717-14603-1-git-send-email-rayagonda.kokatanur@broadcom.com>
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

Add multiple byte read-write support for slave mode.

Signed-off-by: Rayagonda Kokatanur <rayagonda.kokatanur@broadcom.com>
Signed-off-by: Srinath Mannam <srinath.mannam@broadcom.com>
---
 drivers/i2c/busses/i2c-bcm-iproc.c | 117 +++++++++++++++++--------------------
 1 file changed, 53 insertions(+), 64 deletions(-)

diff --git a/drivers/i2c/busses/i2c-bcm-iproc.c b/drivers/i2c/busses/i2c-bcm-iproc.c
index a845b8d..2c7f145 100644
--- a/drivers/i2c/busses/i2c-bcm-iproc.c
+++ b/drivers/i2c/busses/i2c-bcm-iproc.c
@@ -165,12 +165,6 @@ enum i2c_slave_read_status {
 	I2C_SLAVE_RX_END,
 };
 
-enum i2c_slave_xfer_dir {
-	I2C_SLAVE_DIR_READ = 0,
-	I2C_SLAVE_DIR_WRITE,
-	I2C_SLAVE_DIR_NONE,
-};
-
 enum bus_speed_index {
 	I2C_SPD_100K = 0,
 	I2C_SPD_400K,
@@ -203,7 +197,6 @@ struct bcm_iproc_i2c_dev {
 	struct i2c_msg *msg;
 
 	struct i2c_client *slave;
-	enum i2c_slave_xfer_dir xfer_dir;
 
 	/* bytes that have been transferred */
 	unsigned int tx_bytes;
@@ -219,7 +212,8 @@ struct bcm_iproc_i2c_dev {
 		| BIT(IS_M_RX_THLD_SHIFT))
 
 #define ISR_MASK_SLAVE (BIT(IS_S_START_BUSY_SHIFT)\
-		| BIT(IS_S_RX_EVENT_SHIFT) | BIT(IS_S_RD_EVENT_SHIFT))
+		| BIT(IS_S_RX_EVENT_SHIFT) | BIT(IS_S_RD_EVENT_SHIFT)\
+		| BIT(IS_S_TX_UNDERRUN_SHIFT))
 
 static int bcm_iproc_i2c_reg_slave(struct i2c_client *slave);
 static int bcm_iproc_i2c_unreg_slave(struct i2c_client *slave);
@@ -297,15 +291,11 @@ static void bcm_iproc_i2c_slave_init(
 	/* clear all pending slave interrupts */
 	iproc_i2c_wr_reg(iproc_i2c, IS_OFFSET, ISR_MASK_SLAVE);
 
-	/* Enable interrupt register for any READ event */
-	val = BIT(IE_S_RD_EVENT_SHIFT);
 	/* Enable interrupt register to indicate a valid byte in receive fifo */
-	val |= BIT(IE_S_RX_EVENT_SHIFT);
+	val = BIT(IE_S_RX_EVENT_SHIFT);
 	/* Enable interrupt register for the Slave BUSY command */
 	val |= BIT(IE_S_START_BUSY_SHIFT);
 	iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
-
-	iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
 }
 
 static void bcm_iproc_i2c_check_slave_status(
@@ -314,8 +304,11 @@ static void bcm_iproc_i2c_check_slave_status(
 	u32 val;
 
 	val = iproc_i2c_rd_reg(iproc_i2c, S_CMD_OFFSET);
-	val = (val >> S_CMD_STATUS_SHIFT) & S_CMD_STATUS_MASK;
+	/* status is valid only when START_BUSY is cleared after it was set */
+	if (val & BIT(S_CMD_START_BUSY_SHIFT))
+		return;
 
+	val = (val >> S_CMD_STATUS_SHIFT) & S_CMD_STATUS_MASK;
 	if (val == S_CMD_STATUS_TIMEOUT) {
 		dev_err(iproc_i2c->device, "slave random stretch time timeout\n");
 
@@ -327,70 +320,66 @@ static void bcm_iproc_i2c_check_slave_status(
 }
 
 static bool bcm_iproc_i2c_slave_isr(struct bcm_iproc_i2c_dev *iproc_i2c,
-				u32 status)
+				    u32 status)
 {
-	u8 value;
 	u32 val;
-	u32 rd_status;
-	u32 tmp;
+	u8 value, rx_status;
 
-	/* Start of transaction. check address and populate the direction */
-	if (iproc_i2c->xfer_dir == I2C_SLAVE_DIR_NONE) {
-		tmp = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
-		rd_status = (tmp >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
-		/* This condition checks whether the request is a new request */
-		if (((rd_status == I2C_SLAVE_RX_START) &&
-			(status & BIT(IS_S_RX_EVENT_SHIFT))) ||
-			((rd_status == I2C_SLAVE_RX_END) &&
-			(status & BIT(IS_S_RD_EVENT_SHIFT)))) {
-
-			/* Last bit is W/R bit.
-			 * If 1 then its a read request(by master).
-			 */
-			iproc_i2c->xfer_dir = tmp & SLAVE_READ_WRITE_BIT_MASK;
-			if (iproc_i2c->xfer_dir == I2C_SLAVE_DIR_WRITE)
-				i2c_slave_event(iproc_i2c->slave,
-					I2C_SLAVE_READ_REQUESTED, &value);
-			else
-				i2c_slave_event(iproc_i2c->slave,
+	/* Slave RX byte receive */
+	if (status & BIT(IS_S_RX_EVENT_SHIFT)) {
+		val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
+		rx_status = (val >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
+		if (rx_status == I2C_SLAVE_RX_START) {
+			/* Start of SMBUS for Master write */
+			i2c_slave_event(iproc_i2c->slave,
 					I2C_SLAVE_WRITE_REQUESTED, &value);
-		}
-	}
 
-	/* read request from master */
-	if ((status & BIT(IS_S_RD_EVENT_SHIFT)) &&
-		(iproc_i2c->xfer_dir == I2C_SLAVE_DIR_WRITE)) {
-		i2c_slave_event(iproc_i2c->slave,
-			I2C_SLAVE_READ_PROCESSED, &value);
-		iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
+			val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
+			value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
+			i2c_slave_event(iproc_i2c->slave,
+					I2C_SLAVE_WRITE_RECEIVED, &value);
+		} else if (status & BIT(IS_S_RD_EVENT_SHIFT)) {
+			/* Start of SMBUS for Master Read */
+			i2c_slave_event(iproc_i2c->slave,
+					I2C_SLAVE_READ_REQUESTED, &value);
+			iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
 
-		val = BIT(S_CMD_START_BUSY_SHIFT);
-		iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
-	}
+			val = BIT(S_CMD_START_BUSY_SHIFT);
+			iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
 
-	/* write request from master */
-	if ((status & BIT(IS_S_RX_EVENT_SHIFT)) &&
-		(iproc_i2c->xfer_dir == I2C_SLAVE_DIR_READ)) {
-		val = iproc_i2c_rd_reg(iproc_i2c, S_RX_OFFSET);
-		/* Its a write request by Master to Slave.
-		 * We read data present in receive FIFO
-		 */
-		value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
+			/*
+			 * Enable interrupt for TX FIFO becomes empty and
+			 * less than PKT_LENGTH bytes were output on the SMBUS
+			 */
+			val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
+			val |= BIT(IE_S_TX_UNDERRUN_SHIFT);
+			iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
+		} else {
+			/* Master write other than start */
+			value = (u8)((val >> S_RX_DATA_SHIFT) & S_RX_DATA_MASK);
+			i2c_slave_event(iproc_i2c->slave,
+					I2C_SLAVE_WRITE_RECEIVED, &value);
+		}
+	} else if (status & BIT(IS_S_TX_UNDERRUN_SHIFT)) {
+		/* Master read other than start */
 		i2c_slave_event(iproc_i2c->slave,
-			I2C_SLAVE_WRITE_RECEIVED, &value);
-
-		/* check the status for the last byte of the transaction */
-		rd_status = (val >> S_RX_STATUS_SHIFT) & S_RX_STATUS_MASK;
-		if (rd_status == I2C_SLAVE_RX_END)
-			iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
+				I2C_SLAVE_READ_PROCESSED, &value);
 
-		dev_dbg(iproc_i2c->device, "\nread value = 0x%x\n", value);
+		iproc_i2c_wr_reg(iproc_i2c, S_TX_OFFSET, value);
+		val = BIT(S_CMD_START_BUSY_SHIFT);
+		iproc_i2c_wr_reg(iproc_i2c, S_CMD_OFFSET, val);
 	}
 
 	/* Stop */
 	if (status & BIT(IS_S_START_BUSY_SHIFT)) {
 		i2c_slave_event(iproc_i2c->slave, I2C_SLAVE_STOP, &value);
-		iproc_i2c->xfer_dir = I2C_SLAVE_DIR_NONE;
+		/*
+		 * Enable interrupt for TX FIFO becomes empty and
+		 * less than PKT_LENGTH bytes were output on the SMBUS
+		 */
+		val = iproc_i2c_rd_reg(iproc_i2c, IE_OFFSET);
+		val &= ~BIT(IE_S_TX_UNDERRUN_SHIFT);
+		iproc_i2c_wr_reg(iproc_i2c, IE_OFFSET, val);
 	}
 
 	/* clear interrupt status */
-- 
1.9.1