[PATCH v2] serial: pl011: honour serial aliases in device tree

[PATCH v2] serial: pl011: honour serial aliases in device tree

[Matthew Leach]

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: Rob Herring <rob.herring@calxeda.com>
Signed-off-by: Matthew Leach <matthew.leach@arm.com>
---
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..33c90f6 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 index;
+
+	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

Re: [PATCH v2] serial: pl011: honour serial aliases in device tree

[Will Deacon]

Hi Matthew,

On Tue, Aug 21, 2012 at 04:48:14PM +0100, Matthew Leach wrote:
> diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
> index d3553b5..33c90f6 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 index;

May as well return ret here for consistency. With that:

Reviewed-by: Will Deacon <will.deacon-5wv7dgnIgG8@public.gmane.org>

I guess this goes via Greg's tree rather than the ARM one?

Will

Re: [PATCH v2] serial: pl011: honour serial aliases in device tree

[Linus Walleij]

On Tue, Aug 21, 2012 at 5:48 PM, Matthew Leach <matthew.leach@arm.com> wrote:

> 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: Rob Herring <rob.herring@calxeda.com>
> Signed-off-by: Matthew Leach <matthew.leach@arm.com>
> ---
> v2: use IS_ENABLED instead of ifdefs

Looks good to me.
Acked-by: Linus Walleij <linus.walleij@linaro.org>

Yours,
Linus Walleij