Subject: [PATCH] tty: serial: msm_serial: Use DT aliases

From: [email-masked] (Frank Rowand)
Date: Mon, 10 Nov 2014 19:20:23 -0800

On 11/10/2014 6:07 PM, Stephen Boyd wrote:
> On 11/10/2014 05:56 PM, Frank Rowand wrote:
>> On 11/10/2014 11:42 AM, Stephen Boyd wrote:
>>> diff --git a/drivers/tty/serial/msm_serial.c b/drivers/tty/serial/msm_serial.c
>>> index 09364dd8cf3a..d1bc6b6cbc70 100644
>>> --- a/drivers/tty/serial/msm_serial.c
>>> +++ b/drivers/tty/serial/msm_serial.c
>>> @@ -1046,14 +1046,14 @@ static int msm_serial_probe(struct platform_device *pdev)
>>>  	const struct of_device_id *id;
>>>  	int irq, line;
>>>  
>>> -	if (pdev->id == -1)
>>> -		pdev->id = atomic_inc_return(&msm_uart_next_id) - 1;
>>> -
>>>  	if (pdev->dev.of_node)
>>>  		line = of_alias_get_id(pdev->dev.of_node, "serial");
>>>  	else
>>>  		line = pdev->id;
>>>  
>>> +	if (line < 0)
>>> +		line = atomic_inc_return(&msm_uart_next_id) - 1;
>>> +
>>>  	if (unlikely(line < 0 || line >= UART_NR))
>> Then this original check for "line < 0" can also be removed.
>>
>>
> 
> Well this matches what was there before. It would do atomic_inc_return
> if the line was negative and then still check for a negative value. I
> don't mind removing it though. Perhaps we should use an ida?:
> 

OK, you are right.  If (pdev->id < -1) and (!pdev->dev.of_node) then
the check is still needed.

You could use an ida.  Some drivers use a bit map.  I really don't think
this should become a complicated algorithm though.  If the rule is that
either all UARTS have an alias, or no UART has an alias, then I think
the patch could be something like the following.

This combines your original patch, plus your fix patch, plus making
the aliases all or nothing.  Not tested, not even compiled.

What do you think?

Index: linux/drivers/tty/serial/msm_serial.c
===================================================================
--- linux.orig/drivers/tty/serial/msm_serial.c
+++ linux/drivers/tty/serial/msm_serial.c
@@ -1044,17 +1044,28 @@ static int msm_serial_probe(struct platf
 	struct resource *resource;
 	struct uart_port *port;
 	const struct of_device_id *id;
-	int irq;
+	int irq, line;
+	static int no_prev_alias = 1;
 
-	if (pdev->id == -1)
-		pdev->id = atomic_inc_return(&msm_uart_next_id) - 1;
+	if (pdev->dev.of_node) {
+		line = of_alias_get_id(pdev->dev.of_node, "serial");
+		if (line < 0 && no_prev_alias)
+			line = atomic_inc_return(&msm_uart_next_id) - 1;
+		else
+			no_prev_alias = 0;
+	} else {
+		if (pdev->id < 0 && no_prev_alias)
+			line = atomic_inc_return(&msm_uart_next_id) - 1;
+		else
+			line = pdev->id;
+	}
 
-	if (unlikely(pdev->id < 0 || pdev->id >= UART_NR))
+	if (unlikely(line < 0 || line >= UART_NR))
 		return -ENXIO;
 
-	dev_info(&pdev->dev, "msm_serial: detected port #%d\n", pdev->id);
+	dev_info(&pdev->dev, "msm_serial: detected port #%d\n", line);
 
-	port = get_port_from_line(pdev->id);
+	port = get_port_from_line(line);
 	port->dev = &pdev->dev;
 	msm_port = UART_TO_MSM(port);