serial: pl011: honour serial aliases in device tree
authorMatthew Leach <matthew.leach@arm.com>
Tue, 28 Aug 2012 15:41:28 +0000 (16:41 +0100)
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>
Wed, 5 Sep 2012 20:18:12 +0000 (13:18 -0700)
If the order of UART nodes is changed in the device tree, then tty dev
devices are attached to different serial ports causing the console to
be directed to a different physical serial port. The "serial" aliases
in the device tree should prevent this.

This patch ensures that the UART driver creates tty devices that
honour these aliases if a device tree is present.

Acked-by: Linus Walleij <linus.walleij@linaro.org>
Reviewed-by: Will Deacon <will.deacon@arm.com>
Acked-by: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Matthew Leach <matthew.leach@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
drivers/tty/serial/amba-pl011.c

index 3322023..05c15ec 100644 (file)
@@ -52,6 +52,8 @@
 #include <linux/scatterlist.h>
 #include <linux/delay.h>
 #include <linux/types.h>
+#include <linux/of.h>
+#include <linux/of_device.h>
 #include <linux/pinctrl/consumer.h>
 #include <linux/sizes.h>
 
@@ -1862,6 +1864,38 @@ static struct uart_driver amba_reg = {
        .cons                   = AMBA_CONSOLE,
 };
 
+static int pl011_probe_dt_alias(int index, struct device *dev)
+{
+       struct device_node *np;
+       static bool seen_dev_with_alias = false;
+       static bool seen_dev_without_alias = false;
+       int ret = index;
+
+       if (!IS_ENABLED(CONFIG_OF))
+               return ret;
+
+       np = dev->of_node;
+       if (!np)
+               return ret;
+
+       ret = of_alias_get_id(np, "serial");
+       if (IS_ERR_VALUE(ret)) {
+               seen_dev_without_alias = true;
+               ret = index;
+       } else {
+               seen_dev_with_alias = true;
+               if (ret >= ARRAY_SIZE(amba_ports) || amba_ports[ret] != NULL) {
+                       dev_warn(dev, "requested serial port %d  not available.\n", ret);
+                       ret = index;
+               }
+       }
+
+       if (seen_dev_with_alias && seen_dev_without_alias)
+               dev_warn(dev, "aliased and non-aliased serial devices found in device tree. Serial port enumeration may be unpredictable.\n");
+
+       return ret;
+}
+
 static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
 {
        struct uart_amba_port *uap;
@@ -1884,6 +1918,8 @@ static int pl011_probe(struct amba_device *dev, const struct amba_id *id)
                goto out;
        }
 
+       i = pl011_probe_dt_alias(i, &dev->dev);
+
        base = ioremap(dev->res.start, resource_size(&dev->res));
        if (!base) {
                ret = -ENOMEM;