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@xxxxxxxxxx>
Reviewed-by: Will Deacon <will.deacon@xxxxxxx>
Acked-by: Rob Herring <rob.herring@xxxxxxxxxxx>
Signed-off-by: Matthew Leach <matthew.leach@xxxxxxx>
---
v3: minor consistency correction
v2: use IS_ENABLED instead of ifdefs
drivers/tty/serial/amba-pl011.c | 36 ++++++++++++++++++++++++++++++++++++
1 files changed, 36 insertions(+), 0 deletions(-)
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index d3553b5..dc05dd1 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -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>
@@ -1869,6 +1871,38 @@ 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;
@@ -1891,6 +1925,8 @@ 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;
--
1.7.0.4
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