[PATCH v2] i2c: fsi: Create busses for all ports

[Oliver O'Halloran]

Currently we only create an I2C bus for the ports listed in the
device-tree for that master. There's no real reason for this since
we can discover the number of ports the master supports by looking
at the port_max field of the status register.

This patch re-works the bus add logic so that we always create buses
for each port, unless the bus is marked as unavailable in the DT. This
is useful since it ensures that all the buses provided by the CFAM I2C
master are accessible to debug tools.

Cc: Eddie James <eajames at linux.vnet.ibm.com>
Signed-off-by: Oliver O'Halloran <oohall at gmail.com>
---
v2: Fixed off-by-one when calulating the number of ports.
    Compile fixes.
---
 drivers/i2c/busses/i2c-fsi.c | 32 +++++++++++++++++++++++++++-----
 1 file changed, 27 insertions(+), 5 deletions(-)

diff --git a/drivers/i2c/busses/i2c-fsi.c b/drivers/i2c/busses/i2c-fsi.c
index 1e2be2219a60..da5eb3960def 100644
--- a/drivers/i2c/busses/i2c-fsi.c
+++ b/drivers/i2c/busses/i2c-fsi.c
@@ -658,13 +658,29 @@ static const struct i2c_algorithm fsi_i2c_algorithm = {
 	.functionality = fsi_i2c_functionality,
 };
 
+static struct device_node *fsi_i2c_find_port_of_node(struct device_node *fsi,
+						     int port)
+{
+	struct device_node *np;
+	u32 port_no;
+	int rc;
+
+	for_each_child_of_node(fsi, np) {
+		rc = of_property_read_u32(np, "reg", &port_no);
+		if (!rc && port_no == port)
+			return np;
+	}
+
+	return NULL;
+}
+
 static int fsi_i2c_probe(struct device *dev)
 {
 	struct fsi_i2c_master *i2c;
 	struct fsi_i2c_port *port;
 	struct device_node *np;
+	u32 port_no, ports, stat;
 	int rc;
-	u32 port_no;
 
 	i2c = devm_kzalloc(dev, sizeof(*i2c), GFP_KERNEL);
 	if (!i2c)
@@ -678,10 +694,16 @@ static int fsi_i2c_probe(struct device *dev)
 	if (rc)
 		return rc;
 
-	/* Add adapter for each i2c port of the master. */
-	for_each_available_child_of_node(dev->of_node, np) {
-		rc = of_property_read_u32(np, "reg", &port_no);
-		if (rc || port_no > USHRT_MAX)
+	rc = fsi_i2c_read_reg(i2c->fsi, I2C_FSI_STAT, &stat);
+	if (rc)
+		return rc;
+
+	ports = FIELD_GET(I2C_STAT_MAX_PORT, stat) + 1;
+	dev_dbg(dev, "I2C master has %d ports\n", ports);
+
+	for (port_no = 0; port_no < ports; port_no++) {
+		np = fsi_i2c_find_port_of_node(dev->of_node, port_no);
+		if (np && !of_device_is_available(np))
 			continue;
 
 		port = kzalloc(sizeof(*port), GFP_KERNEL);
-- 
2.21.0