[RFC PATCH 0/3] serial: uartps: Add run time support for more IPs than hardcoded 2

[RFC PATCH 0/3] serial: uartps: Add run time support for more IPs than hardcoded 2

[Michal Simek]

Hi,

this series is trying to address discussion I had with Alan in past
https://patchwork.kernel.org/patch/9738445/.

It is moving uart_register_driver() to probe function like it is done in
pl011 driver.
And also introducing new function for alias compatibility checking to
resolve cases where some IPs have alias and some of them not.
This case is detected in pl011_probe_dt_alias() but not properly solved.

Also keep status of free ids/minor numbers in bitmap to know what's the
next unallocated number.

The same solution can be used in pl011, uart16550 and uartlite to really
get unified kernel.

Tested on these use cases:
Notes:
ff000000 is the first PS uart listed in dtsi
ff010000 is the second PS uart listed in dtsi

Standard zcu102 setting
		serial0 = &uart0;
		serial1 = &uart1;
[    0.196628] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.642542] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

Swapped zcu102 setting
		serial0 = &uart1;
		serial1 = &uart0;
[    0.196472] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.196824] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

uart0 on alias higher then MAX uart ports
		serial0 = &uart1;
		serial200 = &uart0;
[    0.176793] ff000000.serial: ttyPS200 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.177288] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

Both uarts on higher aliases
		serial1 = &uart1;
		serial2 = &uart0;
[    0.196470] ff000000.serial: ttyPS2 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.196823] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

uart0 not listed but it is probed first that's why should be ttyPS0 but
there is uart1 via alias
		serial0 = &uart1;
[    0.176656] xuartps ff000000.serial: No serial alias passed. Using
the first free id
[    0.176671] xuartps ff000000.serial: Validate id 0
[    0.176680] xuartps ff000000.serial: The empty id is 0
[    0.176692] xuartps ff000000.serial: ID 0 already taken - skipped
[    0.176701] xuartps ff000000.serial: Validate id 1
[    0.176710] xuartps ff000000.serial: The empty id is 1
[    0.176719] xuartps ff000000.serial: Selected ID 1 allocation passed
[    0.176760] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.177104] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

uart0 not listed but it is probed first that's why should be ttyPS0
		serial1 = &uart1;
[    0.176661] xuartps ff000000.serial: No serial alias passed. Using
the first free id
[    0.176676] xuartps ff000000.serial: Validate id 0
[    0.176686] xuartps ff000000.serial: The empty id is 0
[    0.176696] xuartps ff000000.serial: Selected ID 0 allocation passed
[    0.176737] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.177069] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

uarts not listed in aliases list
[    0.176673] xuartps ff000000.serial: No serial alias passed. Using
the first free id
[    0.176687] xuartps ff000000.serial: Validate id 0
[    0.176697] xuartps ff000000.serial: The empty id is 0
[    0.176707] xuartps ff000000.serial: Selected ID 0 allocation passed
[    0.176746] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
base_baud = 6250000) is a xuartps
[    0.177057] xuartps ff010000.serial: No serial alias passed. Using
the first free id
[    0.177070] xuartps ff010000.serial: Validate id 0
[    0.177079] xuartps ff010000.serial: The empty id is 0
[    0.177089] xuartps ff010000.serial: Selected ID 0 allocation failed
[    0.177098] xuartps ff010000.serial: Validate id 1
[    0.177107] xuartps ff010000.serial: The empty id is 1
[    0.177116] xuartps ff010000.serial: Selected ID 1 allocation passed
[    0.177149] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
base_baud = 6250000) is a xuartps

Thanks,
Michal


Michal Simek (3):
  of: base: Introduce of_alias_check_id() to check alias IDs
  serial: uartps: Move register to probe based on run time detection
  serial: uartps: Change uart ports allocation

 drivers/of/base.c                  |  49 +++++++++++
 drivers/tty/serial/xilinx_uartps.c | 128 +++++++++++++++++++++++------
 include/linux/of.h                 |   2 +
 3 files changed, 153 insertions(+), 26 deletions(-)

-- 
2.17.0

[RFC PATCH 2/3] serial: uartps: Move register to probe based on run time detection

[Michal Simek]

Find out the highest serial alias and allocate that amount of
structures/minor numbers to be able to handle all of them.
Origin setting that there are two prealocated CDNS_UART_NR_PORTS is kept
there.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
---

Discussed here: https://patchwork.kernel.org/patch/9738445/

The same solution is done in pl011 driver.
---
 drivers/tty/serial/xilinx_uartps.c | 32 ++++++++++++++++--------------
 1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index 0fc9de20843c..ffb5b66a05b5 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -1432,6 +1432,22 @@ static int cdns_uart_probe(struct platform_device *pdev)
 	struct cdns_uart *cdns_uart_data;
 	const struct of_device_id *match;
 
+	if (!cdns_uart_uart_driver.state) {
+		rc = of_alias_get_highest_id("serial");
+		if (rc >= CDNS_UART_NR_PORTS) {
+			/* serial2 means 3 ports that's why rc(2) + 1 here */
+			rc += 1;
+			/* Rewrite default setup which is using 2 ports */
+			cdns_uart_uart_driver.nr = rc;
+		}
+
+		rc = uart_register_driver(&cdns_uart_uart_driver);
+		if (rc < 0) {
+			dev_err(&pdev->dev, "Failed to register driver\n");
+			return rc;
+		}
+	}
+
 	cdns_uart_data = devm_kzalloc(&pdev->dev, sizeof(*cdns_uart_data),
 			GFP_KERNEL);
 	if (!cdns_uart_data)
@@ -1622,28 +1638,14 @@ static struct platform_driver cdns_uart_platform_driver = {
 
 static int __init cdns_uart_init(void)
 {
-	int retval = 0;
-
-	/* Register the cdns_uart driver with the serial core */
-	retval = uart_register_driver(&cdns_uart_uart_driver);
-	if (retval)
-		return retval;
-
 	/* Register the platform driver */
-	retval = platform_driver_register(&cdns_uart_platform_driver);
-	if (retval)
-		uart_unregister_driver(&cdns_uart_uart_driver);
-
-	return retval;
+	return platform_driver_register(&cdns_uart_platform_driver);
 }
 
 static void __exit cdns_uart_exit(void)
 {
 	/* Unregister the platform driver */
 	platform_driver_unregister(&cdns_uart_platform_driver);
-
-	/* Unregister the cdns_uart driver */
-	uart_unregister_driver(&cdns_uart_uart_driver);
 }
 
 arch_initcall(cdns_uart_init);
-- 
2.17.0

[RFC PATCH 3/3] serial: uartps: Change uart ports allocation

[Michal Simek]

For ips which have alias algorightm all the tim using that alias and
minor number. It means serial20 alias ends up as ttyPS20.

If aliases are not setup for enabled core the first unused position is
used but that's need to be checked if it is really empty because another
instance doesn't need to be probed. of_alias_check_id() does that test.
If alias pointing to different not compatible IP, it is free to use.

Signed-off-by: Michal Simek <michal.simek@xilinx.com>
---

 drivers/tty/serial/xilinx_uartps.c | 96 ++++++++++++++++++++++++++----
 1 file changed, 85 insertions(+), 11 deletions(-)

diff --git a/drivers/tty/serial/xilinx_uartps.c b/drivers/tty/serial/xilinx_uartps.c
index ffb5b66a05b5..7c616b48c117 100644
--- a/drivers/tty/serial/xilinx_uartps.c
+++ b/drivers/tty/serial/xilinx_uartps.c
@@ -45,6 +45,9 @@ static int rx_timeout = 10;
 module_param(rx_timeout, uint, S_IRUGO);
 MODULE_PARM_DESC(rx_timeout, "Rx timeout, 1-255");
 
+/* The inuse bitfield is recording which IDs are free/used by the driver. */
+static unsigned long *inuse;
+
 /* Register offsets for the UART. */
 #define CDNS_UART_CR		0x00  /* Control Register */
 #define CDNS_UART_MR		0x04  /* Mode Register */
@@ -1418,6 +1421,75 @@ static const struct of_device_id cdns_uart_of_match[] = {
 };
 MODULE_DEVICE_TABLE(of, cdns_uart_of_match);
 
+static int cdns_get_id(struct platform_device *pdev)
+{
+	int id;
+
+	/* Look for a serialN alias */
+	id = of_alias_get_id(pdev->dev.of_node, "serial");
+	if (id < 0) {
+		dev_warn(&pdev->dev,
+			 "No serial alias passed. Using the first free id\n");
+
+		/*
+		 * Start with id 0 and check if there is no serial0 alias
+		 * which points to device which is compatible with this driver.
+		 * If alias exists then try next free position.
+		 */
+		id = 0;
+
+		for (;;) {
+			dev_dbg(&pdev->dev, "Validate id %d\n", id);
+			id = find_next_zero_bit(inuse, id,
+						cdns_uart_uart_driver.nr);
+
+			dev_dbg(&pdev->dev, "The empty id is %d\n", id);
+			/* Check if ID is empty */
+
+			if (of_alias_check_id(cdns_uart_of_match,
+					      "serial", id)) {
+				dev_dbg(&pdev->dev,
+					"ID %d already taken - skipped\n", id);
+				/* Try next one */
+				id++;
+				continue;
+			}
+
+			/* It shouldn't happen anytime */
+			if (id >= cdns_uart_uart_driver.nr) {
+				dev_dbg(&pdev->dev,
+					"ID %d is greater than NR of ports\n",
+					cdns_uart_uart_driver.nr);
+				return -ENXIO;
+			}
+
+			/* Break the loop if bit is taken */
+			if (!test_and_set_bit(id, inuse)) {
+				dev_dbg(&pdev->dev,
+					"Selected ID %d allocation passed\n",
+					id);
+				break;
+			}
+			dev_dbg(&pdev->dev,
+				"Selected ID %d allocation failed\n", id);
+			/* if taking bit fails then try next one */
+			id++;
+		}
+	} else {
+		/*
+		 * If alias was found there is no reason to check
+		 * anything else
+		 */
+		if (test_and_set_bit(id, inuse)) {
+			dev_dbg(&pdev->dev,
+				 "ID %d allocation failed\n", id);
+			return -EAGAIN;
+		}
+	}
+
+	return id;
+}
+
 /**
  * cdns_uart_probe - Platform driver probe
  * @pdev: Pointer to the platform device structure
@@ -1446,6 +1518,13 @@ static int cdns_uart_probe(struct platform_device *pdev)
 			dev_err(&pdev->dev, "Failed to register driver\n");
 			return rc;
 		}
+
+		/* Create bitfield to record which ids are free */
+		inuse = devm_kcalloc(&pdev->dev,
+				     BITS_TO_LONGS(cdns_uart_uart_driver.nr),
+				     sizeof(unsigned long), GFP_KERNEL);
+		if (!inuse)
+			return -ENOMEM;
 	}
 
 	cdns_uart_data = devm_kzalloc(&pdev->dev, sizeof(*cdns_uart_data),
@@ -1463,6 +1542,10 @@ static int cdns_uart_probe(struct platform_device *pdev)
 		cdns_uart_data->quirks = data->quirks;
 	}
 
+	id = cdns_get_id(pdev);
+	if (id < 0)
+		return id;
+
 	cdns_uart_data->pclk = devm_clk_get(&pdev->dev, "pclk");
 	if (IS_ERR(cdns_uart_data->pclk)) {
 		cdns_uart_data->pclk = devm_clk_get(&pdev->dev, "aper_clk");
@@ -1515,16 +1598,6 @@ static int cdns_uart_probe(struct platform_device *pdev)
 				&cdns_uart_data->clk_rate_change_nb))
 		dev_warn(&pdev->dev, "Unable to register clock notifier.\n");
 #endif
-	/* Look for a serialN alias */
-	id = of_alias_get_id(pdev->dev.of_node, "serial");
-	if (id < 0)
-		id = 0;
-
-	if (id >= CDNS_UART_NR_PORTS) {
-		dev_err(&pdev->dev, "Cannot get uart_port structure\n");
-		rc = -ENODEV;
-		goto err_out_notif_unreg;
-	}
 
 	/* At this point, we've got an empty uart_port struct, initialize it */
 	spin_lock_init(&port->lock);
@@ -1583,10 +1656,10 @@ static int cdns_uart_probe(struct platform_device *pdev)
 	return 0;
 
 err_out_pm_disable:
+	clear_bit(port->line, inuse);
 	pm_runtime_disable(&pdev->dev);
 	pm_runtime_set_suspended(&pdev->dev);
 	pm_runtime_dont_use_autosuspend(&pdev->dev);
-err_out_notif_unreg:
 #ifdef CONFIG_COMMON_CLK
 	clk_notifier_unregister(cdns_uart_data->uartclk,
 			&cdns_uart_data->clk_rate_change_nb);
@@ -1618,6 +1691,7 @@ static int cdns_uart_remove(struct platform_device *pdev)
 #endif
 	rc = uart_remove_one_port(&cdns_uart_uart_driver, port);
 	port->mapbase = 0;
+	clear_bit(port->line, inuse);
 	clk_disable_unprepare(cdns_uart_data->uartclk);
 	clk_disable_unprepare(cdns_uart_data->pclk);
 	pm_runtime_disable(&pdev->dev);
-- 
2.17.0

Re: [RFC PATCH 0/3] serial: uartps: Add run time support for more IPs than hardcoded 2

[Maarten Brock]

On 2018-04-26 16:08, Michal Simek wrote:
> Hi,
> 
> this series is trying to address discussion I had with Alan in past
> https://patchwork.kernel.org/patch/9738445/.
> 
> It is moving uart_register_driver() to probe function like it is done 
> in
> pl011 driver.
> And also introducing new function for alias compatibility checking to
> resolve cases where some IPs have alias and some of them not.
> This case is detected in pl011_probe_dt_alias() but not properly 
> solved.
> 
> Also keep status of free ids/minor numbers in bitmap to know what's the
> next unallocated number.
> 
> The same solution can be used in pl011, uart16550 and uartlite to 
> really
> get unified kernel.
> 
> Tested on these use cases:
> Notes:
> ff000000 is the first PS uart listed in dtsi
> ff010000 is the second PS uart listed in dtsi
> 
> Standard zcu102 setting
> 		serial0 = &uart0;
> 		serial1 = &uart1;
> [    0.196628] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.642542] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> Swapped zcu102 setting
> 		serial0 = &uart1;
> 		serial1 = &uart0;
> [    0.196472] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.196824] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> uart0 on alias higher then MAX uart ports
> 		serial0 = &uart1;
> 		serial200 = &uart0;
> [    0.176793] ff000000.serial: ttyPS200 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.177288] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> Both uarts on higher aliases
> 		serial1 = &uart1;
> 		serial2 = &uart0;
> [    0.196470] ff000000.serial: ttyPS2 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.196823] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> uart0 not listed but it is probed first that's why should be ttyPS0 but
> there is uart1 via alias
> 		serial0 = &uart1;
> [    0.176656] xuartps ff000000.serial: No serial alias passed. Using
> the first free id
> [    0.176671] xuartps ff000000.serial: Validate id 0
> [    0.176680] xuartps ff000000.serial: The empty id is 0
> [    0.176692] xuartps ff000000.serial: ID 0 already taken - skipped
> [    0.176701] xuartps ff000000.serial: Validate id 1
> [    0.176710] xuartps ff000000.serial: The empty id is 1
> [    0.176719] xuartps ff000000.serial: Selected ID 1 allocation passed
> [    0.176760] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.177104] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> uart0 not listed but it is probed first that's why should be ttyPS0
> 		serial1 = &uart1;
> [    0.176661] xuartps ff000000.serial: No serial alias passed. Using
> the first free id
> [    0.176676] xuartps ff000000.serial: Validate id 0
> [    0.176686] xuartps ff000000.serial: The empty id is 0
> [    0.176696] xuartps ff000000.serial: Selected ID 0 allocation passed
> [    0.176737] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.177069] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> uarts not listed in aliases list
> [    0.176673] xuartps ff000000.serial: No serial alias passed. Using
> the first free id
> [    0.176687] xuartps ff000000.serial: Validate id 0
> [    0.176697] xuartps ff000000.serial: The empty id is 0
> [    0.176707] xuartps ff000000.serial: Selected ID 0 allocation passed
> [    0.176746] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
> base_baud = 6250000) is a xuartps
> [    0.177057] xuartps ff010000.serial: No serial alias passed. Using
> the first free id
> [    0.177070] xuartps ff010000.serial: Validate id 0
> [    0.177079] xuartps ff010000.serial: The empty id is 0
> [    0.177089] xuartps ff010000.serial: Selected ID 0 allocation failed
> [    0.177098] xuartps ff010000.serial: Validate id 1
> [    0.177107] xuartps ff010000.serial: The empty id is 1
> [    0.177116] xuartps ff010000.serial: Selected ID 1 allocation passed
> [    0.177149] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
> base_baud = 6250000) is a xuartps
> 
> Thanks,
> Michal

Hello Michal,

How will this interact with ns16550 based UARTs?

Can we have both /dev/ttyS0 and /dev/ttyPS0?
Currently we can't unless we create *no* serialN alias for the ns16550.
And there is no other means to lock the /dev/ttySx name to a device 
either.

Or will the xuartps driver eventually use /dev/ttySx as well?

Maarten

Re: [RFC PATCH 0/3] serial: uartps: Add run time support for more IPs than hardcoded 2

[Michal Simek]

Hi,

On 5.5.2018 15:10, Maarten Brock wrote:
> On 2018-04-26 16:08, Michal Simek wrote:
>> Hi,
>>
>> this series is trying to address discussion I had with Alan in past
>> https://patchwork.kernel.org/patch/9738445/.
>>
>> It is moving uart_register_driver() to probe function like it is done in
>> pl011 driver.
>> And also introducing new function for alias compatibility checking to
>> resolve cases where some IPs have alias and some of them not.
>> This case is detected in pl011_probe_dt_alias() but not properly solved.
>>
>> Also keep status of free ids/minor numbers in bitmap to know what's the
>> next unallocated number.
>>
>> The same solution can be used in pl011, uart16550 and uartlite to really
>> get unified kernel.
>>
>> Tested on these use cases:
>> Notes:
>> ff000000 is the first PS uart listed in dtsi
>> ff010000 is the second PS uart listed in dtsi
>>
>> Standard zcu102 setting
>>         serial0 = &uart0;
>>         serial1 = &uart1;
>> [    0.196628] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.642542] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> Swapped zcu102 setting
>>         serial0 = &uart1;
>>         serial1 = &uart0;
>> [    0.196472] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.196824] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> uart0 on alias higher then MAX uart ports
>>         serial0 = &uart1;
>>         serial200 = &uart0;
>> [    0.176793] ff000000.serial: ttyPS200 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.177288] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> Both uarts on higher aliases
>>         serial1 = &uart1;
>>         serial2 = &uart0;
>> [    0.196470] ff000000.serial: ttyPS2 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.196823] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> uart0 not listed but it is probed first that's why should be ttyPS0 but
>> there is uart1 via alias
>>         serial0 = &uart1;
>> [    0.176656] xuartps ff000000.serial: No serial alias passed. Using
>> the first free id
>> [    0.176671] xuartps ff000000.serial: Validate id 0
>> [    0.176680] xuartps ff000000.serial: The empty id is 0
>> [    0.176692] xuartps ff000000.serial: ID 0 already taken - skipped
>> [    0.176701] xuartps ff000000.serial: Validate id 1
>> [    0.176710] xuartps ff000000.serial: The empty id is 1
>> [    0.176719] xuartps ff000000.serial: Selected ID 1 allocation passed
>> [    0.176760] ff000000.serial: ttyPS1 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.177104] ff010000.serial: ttyPS0 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> uart0 not listed but it is probed first that's why should be ttyPS0
>>         serial1 = &uart1;
>> [    0.176661] xuartps ff000000.serial: No serial alias passed. Using
>> the first free id
>> [    0.176676] xuartps ff000000.serial: Validate id 0
>> [    0.176686] xuartps ff000000.serial: The empty id is 0
>> [    0.176696] xuartps ff000000.serial: Selected ID 0 allocation passed
>> [    0.176737] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.177069] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> uarts not listed in aliases list
>> [    0.176673] xuartps ff000000.serial: No serial alias passed. Using
>> the first free id
>> [    0.176687] xuartps ff000000.serial: Validate id 0
>> [    0.176697] xuartps ff000000.serial: The empty id is 0
>> [    0.176707] xuartps ff000000.serial: Selected ID 0 allocation passed
>> [    0.176746] ff000000.serial: ttyPS0 at MMIO 0xff000000 (irq = 33,
>> base_baud = 6250000) is a xuartps
>> [    0.177057] xuartps ff010000.serial: No serial alias passed. Using
>> the first free id
>> [    0.177070] xuartps ff010000.serial: Validate id 0
>> [    0.177079] xuartps ff010000.serial: The empty id is 0
>> [    0.177089] xuartps ff010000.serial: Selected ID 0 allocation failed
>> [    0.177098] xuartps ff010000.serial: Validate id 1
>> [    0.177107] xuartps ff010000.serial: The empty id is 1
>> [    0.177116] xuartps ff010000.serial: Selected ID 1 allocation passed
>> [    0.177149] ff010000.serial: ttyPS1 at MMIO 0xff010000 (irq = 34,
>> base_baud = 6250000) is a xuartps
>>
>> Thanks,
>> Michal
> 
> Hello Michal,
> 
> How will this interact with ns16550 based UARTs?
> 
> Can we have both /dev/ttyS0 and /dev/ttyPS0?
> Currently we can't unless we create *no* serialN alias for the ns16550.
> And there is no other means to lock the /dev/ttySx name to a device either.
> 
> Or will the xuartps driver eventually use /dev/ttySx as well?

I am not changing any current behavior in this case. uartps is using
ttyPS. ns16550 is using ttyS and on xilinx devices we are using also
ttyUL for uartlite. Other drivers are using different names.

Thanks,
Michal