[PATCH v12 5/8] i2c: fsi: Add transfer implementation

[Eddie James <eajames@linux.vnet.ibm.com>]

From: "eajames@linux.vnet.ibm.com" <eajames@linux.vnet.ibm.com>

Execute I2C transfers from the FSI-attached I2C master. Use polling
instead of interrupts as we have no hardware IRQ over FSI.

Signed-off-by: Eddie James <eajames@linux.vnet.ibm.com>
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>
---
 drivers/i2c/busses/i2c-fsi.c | 195 ++++++++++++++++++++++++++++++++++++++++++-
 1 file changed, 193 insertions(+), 2 deletions(-)

diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
index 0f0bc88..45a6ebd 100644
--- a/drivers/i2c/busses/i2c-fsi.c
+++ b/drivers/i2c/busses/i2c-fsi.c
@@ -155,6 +155,7 @@ struct fsi_i2c_port {
 	struct i2c_adapter	adapter;
 	struct fsi_i2c_master	*master;
 	u16			port;
+	u16			xfrd;
 };
 
 static int fsi_i2c_read_reg(struct fsi_device *fsi, unsigned int reg,
@@ -230,6 +231,99 @@ static int fsi_i2c_set_port(struct fsi_i2c_port *port)
 	return fsi_i2c_write_reg(fsi, I2C_FSI_RESET_ERR, &dummy);
 }
 
+static int fsi_i2c_start(struct fsi_i2c_port *port, struct i2c_msg *msg,
+			 bool stop)
+{
+	struct fsi_i2c_master *i2c = port->master;
+	u32 cmd = I2C_CMD_WITH_START | I2C_CMD_WITH_ADDR;
+
+	port->xfrd = 0;
+
+	if (msg->flags & I2C_M_RD)
+		cmd |= I2C_CMD_READ;
+
+	if (stop || msg->flags & I2C_M_STOP)
+		cmd |= I2C_CMD_WITH_STOP;
+
+	cmd |= FIELD_PREP(I2C_CMD_ADDR, msg->addr);
+	cmd |= FIELD_PREP(I2C_CMD_LEN, msg->len);
+
+	return fsi_i2c_write_reg(i2c->fsi, I2C_FSI_CMD, &cmd);
+}
+
+static int fsi_i2c_get_op_bytes(int op_bytes)
+{
+	/* fsi is limited to max 4 byte aligned ops */
+	if (op_bytes > 4)
+		return 4;
+	else if (op_bytes == 3)
+		return 2;
+	return op_bytes;
+}
+
+static int fsi_i2c_write_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
+			      u8 fifo_count)
+{
+	int write;
+	int rc;
+	struct fsi_i2c_master *i2c = port->master;
+	int bytes_to_write = i2c->fifo_size - fifo_count;
+	int bytes_remaining = msg->len - port->xfrd;
+
+	bytes_to_write = min(bytes_to_write, bytes_remaining);
+
+	while (bytes_to_write) {
+		write = fsi_i2c_get_op_bytes(bytes_to_write);
+
+		rc = fsi_device_write(i2c->fsi, I2C_FSI_FIFO,
+				      &msg->buf[port->xfrd], write);
+		if (rc)
+			return rc;
+
+		port->xfrd += write;
+		bytes_to_write -= write;
+	}
+
+	return 0;
+}
+
+static int fsi_i2c_read_fifo(struct fsi_i2c_port *port, struct i2c_msg *msg,
+			     u8 fifo_count)
+{
+	int read;
+	int rc;
+	struct fsi_i2c_master *i2c = port->master;
+	int bytes_to_read;
+	int xfr_remaining = msg->len - port->xfrd;
+	u32 dummy;
+
+	bytes_to_read = min_t(int, fifo_count, xfr_remaining);
+
+	while (bytes_to_read) {
+		read = fsi_i2c_get_op_bytes(bytes_to_read);
+
+		if (xfr_remaining) {
+			rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO,
+					     &msg->buf[port->xfrd], read);
+			if (rc)
+				return rc;
+
+			port->xfrd += read;
+			xfr_remaining -= read;
+		} else {
+			/* no more buffer but data in fifo, need to clear it */
+			rc = fsi_device_read(i2c->fsi, I2C_FSI_FIFO, &dummy,
+					     read);
+			if (rc)
+				return rc;
+		}
+
+		bytes_to_read -= read;
+	}
+
+	return 0;
+}
+
 static int fsi_i2c_reset_engine(struct fsi_i2c_master *i2c, u16 port)
 {
 	int rc;
@@ -305,17 +399,114 @@ static int fsi_i2c_abort(struct fsi_i2c_port *port, u32 status)
 	return -ETIMEDOUT;
 }
 
+static int fsi_i2c_handle_status(struct fsi_i2c_port *port,
+				 struct i2c_msg *msg, u32 status)
+{
+	int rc;
+	u8 fifo_count;
+
+	if (status & I2C_STAT_ERR) {
+		rc = fsi_i2c_abort(port, status);
+		if (rc)
+			return rc;
+
+		if (status & I2C_STAT_INV_CMD)
+			return -EINVAL;
+
+		if (status & (I2C_STAT_PARITY | I2C_STAT_BE_OVERRUN |
+		    I2C_STAT_BE_ACCESS))
+			return -EPROTO;
+
+		if (status & I2C_STAT_NACK)
+			return -ENXIO;
+
+		if (status & I2C_STAT_LOST_ARB)
+			return -EAGAIN;
+
+		if (status & I2C_STAT_STOP_ERR)
+			return -EBADMSG;
+
+		return -EIO;
+	}
+
+	if (status & I2C_STAT_DAT_REQ) {
+		fifo_count = FIELD_GET(I2C_STAT_FIFO_COUNT, status);
+
+		if (msg->flags & I2C_M_RD)
+			return fsi_i2c_read_fifo(port, msg, fifo_count);
+
+		return fsi_i2c_write_fifo(port, msg, fifo_count);
+	}
+
+	if (status & I2C_STAT_CMD_COMP) {
+		if (port->xfrd < msg->len)
+			return -ENODATA;
+
+		return msg->len;
+	}
+
+	return 0;
+}
+
+static int fsi_i2c_wait(struct fsi_i2c_port *port, struct i2c_msg *msg,
+			unsigned long timeout)
+{
+	u32 status = 0;
+	int rc;
+	unsigned long start = jiffies;
+
+	do {
+		rc = fsi_i2c_read_reg(port->master->fsi, I2C_FSI_STAT,
+				      &status);
+		if (rc)
+			return rc;
+
+		if (status & I2C_STAT_ANY_RESP) {
+			rc = fsi_i2c_handle_status(port, msg, status);
+			if (rc < 0)
+				return rc;
+
+			/* cmd complete and all data xfrd */
+			if (rc == msg->len)
+				return 0;
+
+			/* need to xfr more data, but maybe don't need wait */
+			continue;
+		}
+
+		usleep_range(I2C_CMD_SLEEP_MIN_US, I2C_CMD_SLEEP_MAX_US);
+	} while (time_after(start + timeout, jiffies));
+
+	return -ETIMEDOUT;
+}
+
 static int fsi_i2c_xfer(struct i2c_adapter *adap, struct i2c_msg *msgs,
 			int num)
 {
-	int rc;
+	int i, rc;
+	unsigned long start_time;
 	struct fsi_i2c_port *port = adap->algo_data;
+	struct i2c_msg *msg;
 
 	rc = fsi_i2c_set_port(port);
 	if (rc)
 		return rc;
 
-	return -EOPNOTSUPP;
+	for (i = 0; i < num; i++) {
+		msg = msgs + i;
+		start_time = jiffies;
+
+		rc = fsi_i2c_start(port, msg, i == num - 1);
+		if (rc)
+			return rc;
+
+		rc = fsi_i2c_wait(port, msg,
+				  adap->timeout - (jiffies - start_time));
+		if (rc)
+			return rc;
+	}
+
+	return num;
 }
 
 static u32 fsi_i2c_functionality(struct i2c_adapter *adap)
-- 
1.8.3.1