[PATCH v4 0/4] ACPI: parse the SPCR table

[PATCH v4 0/4] ACPI: parse the SPCR table

[Aleksey Makarov]

'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
Console Redirection Table) [2] as a mandatory ACPI table that
specifies the configuration of serial console.

Introduce a new function acpi_console_check().  At the uart port
registration, this function checks if the ACPI SPCR table specifies
its argument of type struct uart_port to be a console
and if so calls add_preferred_console().

Use SPCR to tell if SBSA serial driver should use 32-bit access to registers.

Based on the work by Leif Lindholm [3]

Should be applied to next-20160229.

Tested on QEMU.  SPCR support is included in QEMU's ARM mach-virt
since 2.4 release.

v4:
- drop patch "ACPI: change __init to __ref for early_acpi_os_unmap_memory()"
  ACPI developers work on a new API and asked not to do that.
  Instead, use acpi_get_table_with_size()/early_acpi_os_unmap_memory() once
  and cache the result. (Lv Zheng)
- fix some style issues (Yury Norov)

v3:
https://lkml.kernel.org/g/1455559532-8305-1-git-send-email-aleksey.makarov at linaro.org

Greg Kroah-Hartman did not like v2 so I have rewritten this patchset:

- drop acpi_match() member of struct console
- drop implementations of this member for pl011 and 8250
- drop the patch that renames some vars in printk.c as it is not needed anymore
- drop patch that introduces system wide acpi_table_parse2().
  Instead introduce a custom acpi_table_parse_spcr() in spcr.c

Instead of introducing a new match_acpi() member of struct console,
this patchset introduces a new function acpi_console_check().
This function is called when a new uart is registered at serial_core.c
the same way OF code checks for console.  If the registered uart is the
console specified by SPCR table, this function calls add_preferred_console()

The restrictions of this approach are:

- only serial consoles can be set up
- only consoles specified by the memory/io address can be set up
  (SPCR can specify devices by PCI id/PCI address)

v2:
https://lkml.kernel.org/g/1455299022-11641-1-git-send-email-aleksey.makarov at linaro.org
- don't use SPCR if user specified console in command line
- fix initialization order of newcon->index = 0
- rename some variables at printk.c (Joe Perches, Peter Hurley)
- enable ACPI_SPCR_TABLE in a separate patch (Andy Shevchenko)
- remove the retry loop for console registering (Peter Hurley).
  Instead, obtain SPCR with acpi_get_table().  That works after
  call to acpi_early_init() i. e. in any *_initcall()
- describe design decision behind introducing acpi_match() (Peter Hurley)
- fix compilation for x86 + ACPI (Graeme Gregory)
- introduce DBG2 constants in a separate patch (Andy Shevchenko)
- fix a typo in DBG2 constants (Andy Shevchenko)
- add ACPI_DBG2_ARM_SBSA_32BIT constant (Christopher Covington)
- add support for ACPI_DBG2_ARM_SBSA_* consoles (Christopher Covington)
- add documentation for functions
- add a patch that uses SPCR to find if SBSA serial driver should use 32-bit
  accessor functions (Christopher Covington)
- change __init to __ref for early_acpi_os_unmap_memory() in a separate patch
- introduce acpi_table_parse2() in a separate patch
- fix fetching the SPCR table early (Mark Salter)
- add a patch from Mark Salter that introduces support for matching 8250-based
  consoles

v1:
https://lkml.kernel.org/g/1453722324-22407-1-git-send-email-aleksey.makarov at linaro.org

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
[2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
[3] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm at linaro.org

Aleksey Makarov (4):
  ACPI: parse SPCR and enable matching console
  ACPI: enable ACPI_SPCR_TABLE on ARM64
  ACPI: add definitions of DBG2 subtypes
  serial: pl011: use ACPI SPCR to setup 32-bit access

 arch/arm64/Kconfig               |   1 +
 drivers/acpi/Kconfig             |   3 +
 drivers/acpi/Makefile            |   1 +
 drivers/acpi/spcr.c              | 138 +++++++++++++++++++++++++++++++++++++++
 drivers/tty/serial/amba-pl011.c  |   2 +
 drivers/tty/serial/serial_core.c |  14 +++-
 include/acpi/actbl2.h            |   5 ++
 include/linux/acpi.h             |  15 +++++
 8 files changed, 177 insertions(+), 2 deletions(-)
 create mode 100644 drivers/acpi/spcr.c

-- 
2.7.1

[PATCH v4 1/4] ACPI: parse SPCR and enable matching console

[Aleksey Makarov]

'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port
Console Redirection Table) [2] as a mandatory ACPI table that
specifies the configuration of serial console.

Parse this table and check if any registered console match the
description.  If it does, enable that console.

Introduce a new function acpi_console_check().  At the uart port
registration, this function checks if the ACPI SPCR table specifies
its argument of type struct uart_port to be a console
and if so calls add_preferred_console().

[1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
[2] http://msdn.microsoft.com/en-us/library/windows/hardware/dn639131(v=vs.85).aspx

Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
---
 drivers/acpi/Kconfig             |   3 +
 drivers/acpi/Makefile            |   1 +
 drivers/acpi/spcr.c              | 116 +++++++++++++++++++++++++++++++++++++++
 drivers/tty/serial/serial_core.c |  14 ++++-
 include/linux/acpi.h             |  10 ++++
 5 files changed, 142 insertions(+), 2 deletions(-)
 create mode 100644 drivers/acpi/spcr.c

diff --git a/drivers/acpi/Kconfig b/drivers/acpi/Kconfig
index 65fb483..5611eb6 100644
--- a/drivers/acpi/Kconfig
+++ b/drivers/acpi/Kconfig
@@ -77,6 +77,9 @@ config ACPI_DEBUGGER_USER
 
 endif
 
+config ACPI_SPCR_TABLE
+	bool
+
 config ACPI_SLEEP
 	bool
 	depends on SUSPEND || HIBERNATION
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index 7395928..f70ae14 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -82,6 +82,7 @@ obj-$(CONFIG_ACPI_EC_DEBUGFS)	+= ec_sys.o
 obj-$(CONFIG_ACPI_CUSTOM_METHOD)+= custom_method.o
 obj-$(CONFIG_ACPI_BGRT)		+= bgrt.o
 obj-$(CONFIG_ACPI_CPPC_LIB)	+= cppc_acpi.o
+obj-$(CONFIG_ACPI_SPCR_TABLE)	+= spcr.o
 obj-$(CONFIG_ACPI_DEBUGGER_USER) += acpi_dbg.o
 
 # processor has its own "processor." module_param namespace
diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
new file mode 100644
index 0000000..c460cb1
--- /dev/null
+++ b/drivers/acpi/spcr.c
@@ -0,0 +1,116 @@
+/*
+ * Copyright (c) 2012, Intel Corporation
+ * Copyright (c) 2015, Red Hat, Inc.
+ * Copyright (c) 2015, 2016 Linaro Ltd.
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ */
+
+#define pr_fmt(fmt) "ACPI: SPCR: " fmt
+
+#include <linux/acpi.h>
+#include <linux/console.h>
+#include <linux/kernel.h>
+#include <linux/serial_core.h>
+
+static char *options;
+static struct acpi_generic_address address;
+
+static int __init parse_spcr_init(void)
+{
+	struct acpi_table_spcr *table;
+	acpi_size table_size;
+	acpi_status status;
+	int err = 0;
+
+	status = acpi_get_table_with_size(ACPI_SIG_SPCR, 0,
+					  (struct acpi_table_header **)&table,
+					  &table_size);
+
+	if (ACPI_FAILURE(status)) {
+		pr_err("could not get the table\n");
+		return -ENOENT;
+	}
+
+	if (table->header.revision < 2) {
+		err = -EINVAL;
+		pr_err("wrong table version\n");
+		goto done;
+	}
+
+	switch (table->baud_rate) {
+	case 3:
+		options = "9600";
+		break;
+	case 4:
+		options = "19200";
+		break;
+	case 6:
+		options = "57600";
+		break;
+	case 7:
+		options = "115200";
+		break;
+	default:
+		options = "";
+		break;
+	}
+
+	address = table->serial_port;
+
+done:
+	early_acpi_os_unmap_memory((void __iomem *)table, table_size);
+	return err;
+}
+
+/*
+ * This function calls __init parse_spcr_init() so it needs __ref.
+ * It is referenced by the arch_inicall() macros so it will be called
+ * at initialization and the 'parsed' variable will be set.
+ * So it's safe to make it __ref.
+ */
+static int __ref parse_spcr(void)
+{
+	static bool parsed;
+	static int parse_error;
+
+	if (!parsed) {
+		parse_error = parse_spcr_init();
+		parsed = true;
+	}
+
+	return parse_error;
+}
+
+arch_initcall(parse_spcr);
+
+/**
+ * acpi_console_check - Check if uart matches the console specified by SPCR.
+ *
+ * @uport:	uart port to check
+ *
+ * This function checks if the ACPI SPCR table specifies @uport to be a console
+ * and if so calls add_preferred_console()
+ *
+ * Return: a non-error value if the console matches.
+ */
+bool acpi_console_check(struct uart_port *uport)
+{
+	if (acpi_disabled || console_set_on_cmdline || parse_spcr() < 0)
+		return false;
+
+	if ((address.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY &&
+	     address.address == (u64)uport->mapbase) ||
+	    (address.space_id == ACPI_ADR_SPACE_SYSTEM_IO &&
+	     address.address == (u64)uport->iobase)) {
+		pr_info("adding preferred console [%s%d]\n", uport->cons->name,
+			uport->line);
+		add_preferred_console(uport->cons->name, uport->line, options);
+		return true;
+	}
+
+	return false;
+}
diff --git a/drivers/tty/serial/serial_core.c b/drivers/tty/serial/serial_core.c
index a126a60..459ab54 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -34,6 +34,7 @@
 #include <linux/serial_core.h>
 #include <linux/delay.h>
 #include <linux/mutex.h>
+#include <linux/acpi.h>
 
 #include <asm/irq.h>
 #include <asm/uaccess.h>
@@ -2654,8 +2655,17 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
 		spin_lock_init(&uport->lock);
 		lockdep_set_class(&uport->lock, &port_lock_key);
 	}
-	if (uport->cons && uport->dev)
-		of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
+
+	/*
+	 * Support both open FW and ACPI access to console definitions.
+	 * Both of_console_check() and acpi_console_check() will call
+	 * add_preferred_console() if a console definition is found.
+	 */
+	if (uport->cons && uport->dev) {
+		if (!acpi_console_check(uport))
+			of_console_check(uport->dev->of_node, uport->cons->name,
+					 uport->line);
+	}
 
 	uart_configure_port(drv, state, uport);
 
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index 06ed7e5..ea0c297 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1004,4 +1004,14 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
 #define acpi_probe_device_table(t)	({ int __r = 0; __r;})
 #endif
 
+struct uart_port;
+#ifdef CONFIG_ACPI_SPCR_TABLE
+bool acpi_console_check(struct uart_port *uport);
+#else
+static inline bool acpi_console_check(struct uart_port *uport)
+{
+	return FALSE;
+}
+#endif
+
 #endif	/*_LINUX_ACPI_H*/
-- 
2.7.1

[PATCH v4 2/4] ACPI: enable ACPI_SPCR_TABLE on ARM64

[Aleksey Makarov]

SBBR mentions SPCR as a mandatory ACPI table.
So enable it for ARM64

Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
---
 arch/arm64/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 9dc5209..544af2e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -3,6 +3,7 @@ config ARM64
 	select ACPI_CCA_REQUIRED if ACPI
 	select ACPI_GENERIC_GSI if ACPI
 	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
+	select ACPI_SPCR_TABLE if ACPI
 	select ARCH_HAS_DEVMEM_IS_ALLOWED
 	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
 	select ARCH_HAS_ELF_RANDOMIZE
-- 
2.7.1

[PATCH v4 3/4] ACPI: add definitions of DBG2 subtypes

[Aleksey Makarov]

The recent version of Microsoft Debug Port Table 2 (DBG2) [1]
specifies additional serial debug port subtypes.  These constants
are also referred by Serial Port Console Redirection Table (SPCR) [2]

Add these constants.

[1] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639131(v=vs.85).aspx
[2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx

Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
---
 include/acpi/actbl2.h | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/include/acpi/actbl2.h b/include/acpi/actbl2.h
index a4ef625..652f747 100644
--- a/include/acpi/actbl2.h
+++ b/include/acpi/actbl2.h
@@ -371,6 +371,11 @@ struct acpi_dbg2_device {
 
 #define ACPI_DBG2_16550_COMPATIBLE  0x0000
 #define ACPI_DBG2_16550_SUBSET      0x0001
+#define ACPI_DBG2_ARM_PL011         0x0003
+#define ACPI_DBG2_ARM_SBSA_32BIT    0x000D
+#define ACPI_DBG2_ARM_SBSA_GENERIC  0x000E
+#define ACPI_DBG2_ARM_DCC           0x000F
+#define ACPI_DBG2_BCM2835           0x0010
 
 #define ACPI_DBG2_1394_STANDARD     0x0000
 
-- 
2.7.1

[PATCH v4 4/4] serial: pl011: use ACPI SPCR to setup 32-bit access

[Aleksey Makarov]

Some implementations of ARM SBSA serial port hardware require that access
to the registers should be 32-bit.  Unfortunately, the only way for
the driver to tell if it's the case is to use the data from ACPI SPCR/DBG2
tables.  In this case the value of the 'Interface Type' field of the SPCR
table is ACPI_DBG2_ARM_SBSA_32BIT.

How this value is described in the DBG2 spec:
"(deprecated) ARM SBSA (2.x only) Generic UART supporting only
32-bit accesses"

Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
---
 drivers/acpi/spcr.c             | 22 ++++++++++++++++++++++
 drivers/tty/serial/amba-pl011.c |  2 ++
 include/linux/acpi.h            |  5 +++++
 3 files changed, 29 insertions(+)

diff --git a/drivers/acpi/spcr.c b/drivers/acpi/spcr.c
index c460cb1..f2e81af 100644
--- a/drivers/acpi/spcr.c
+++ b/drivers/acpi/spcr.c
@@ -18,6 +18,7 @@
 
 static char *options;
 static struct acpi_generic_address address;
+static bool sbsa_32_bit;
 
 static int __init parse_spcr_init(void)
 {
@@ -60,6 +61,7 @@ static int __init parse_spcr_init(void)
 	}
 
 	address = table->serial_port;
+	sbsa_32_bit = table->interface_type == ACPI_DBG2_ARM_SBSA_32BIT;
 
 done:
 	early_acpi_os_unmap_memory((void __iomem *)table, table_size);
@@ -114,3 +116,23 @@ bool acpi_console_check(struct uart_port *uport)
 
 	return false;
 }
+
+/**
+ * acpi_console_sbsa_32bit - Tell if SPCR specifies 32-bit SBSA.
+ *
+ * Some implementations of ARM SBSA serial port hardware require that access
+ * to the registers should be 32-bit.  Unfortunately, the only way for
+ * the driver to tell if it's the case is to use the data from ACPI SPCR/DBG2
+ * tables.  In this case the value of the 'Interface Type' field of the SPCR
+ * table is ACPI_DBG2_ARM_SBSA_32BIT.
+ *
+ * Return: true if access should be 32-bit wide.
+ */
+bool acpi_console_sbsa_32bit(void)
+{
+	if (acpi_disabled || parse_spcr() < 0)
+		return false;
+
+	return sbsa_32_bit;
+}
+EXPORT_SYMBOL(acpi_console_sbsa_32bit);
diff --git a/drivers/tty/serial/amba-pl011.c b/drivers/tty/serial/amba-pl011.c
index 500232a..d9ca3a4 100644
--- a/drivers/tty/serial/amba-pl011.c
+++ b/drivers/tty/serial/amba-pl011.c
@@ -2541,6 +2541,8 @@ static int sbsa_uart_probe(struct platform_device *pdev)
 		baudrate = 115200;
 	}
 
+	vendor_sbsa.access_32b = acpi_console_sbsa_32bit();
+
 	portnr = pl011_find_free_port();
 	if (portnr < 0)
 		return portnr;
diff --git a/include/linux/acpi.h b/include/linux/acpi.h
index ea0c297..da1eb23 100644
--- a/include/linux/acpi.h
+++ b/include/linux/acpi.h
@@ -1007,11 +1007,16 @@ static inline struct fwnode_handle *acpi_get_next_subnode(struct device *dev,
 struct uart_port;
 #ifdef CONFIG_ACPI_SPCR_TABLE
 bool acpi_console_check(struct uart_port *uport);
+bool acpi_console_sbsa_32bit(void);
 #else
 static inline bool acpi_console_check(struct uart_port *uport)
 {
 	return FALSE;
 }
+static inline bool acpi_console_sbsa_32bit(void)
+{
+	return false;
+}
 #endif
 
 #endif	/*_LINUX_ACPI_H*/
-- 
2.7.1

[PATCH v4 1/4] ACPI: parse SPCR and enable matching console

[Andy Shevchenko]

On Mon, Feb 29, 2016 at 2:02 PM, Aleksey Makarov
<aleksey.makarov@linaro.org> wrote:
> 'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port
> Console Redirection Table) [2] as a mandatory ACPI table that
> specifies the configuration of serial console.
>
> Parse this table and check if any registered console match the
> description.  If it does, enable that console.
>
> Introduce a new function acpi_console_check().  At the uart port
> registration, this function checks if the ACPI SPCR table specifies
> its argument of type struct uart_port to be a console
> and if so calls add_preferred_console().

> +       if (ACPI_FAILURE(status)) {
> +               pr_err("could not get the table\n");

Is it worse to have on error level? Is it possible to have firmware
without this table? I think it would be a normal case for non-arm
world.
I'm also not sure if this message useful even on warn level.

> +               return -ENOENT;
> +       }
> +
> +       if (table->header.revision < 2) {
> +               err = -EINVAL;
> +               pr_err("wrong table version\n");

And this one quite good to have, indeed.

> + * acpi_console_check - Check if uart matches the console specified by SPCR.
> + *
> + * @uport:     uart port to check
> + *

Since you use sections, you may add:
+ * Description:

> + * This function checks if the ACPI SPCR table specifies @uport to be a console
> + * and if so calls add_preferred_console()
> + *
> + * Return: a non-error value if the console matches.

> @@ -2654,8 +2655,17 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
>                 spin_lock_init(&uport->lock);
>                 lockdep_set_class(&uport->lock, &port_lock_key);
>         }
> -       if (uport->cons && uport->dev)
> -               of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
> +
> +       /*
> +        * Support both open FW and ACPI access to console definitions.
> +        * Both of_console_check() and acpi_console_check() will call
> +        * add_preferred_console() if a console definition is found.
> +        */
> +       if (uport->cons && uport->dev) {
> +               if (!acpi_console_check(uport))

if (cond1) {
 if (cond2) {
...
 }
}

is equivalent to
if (cond1 && cond2) {
...
}

> +                       of_console_check(uport->dev->of_node, uport->cons->name,
> +                                        uport->line);
> +       }



-- 
With Best Regards,
Andy Shevchenko

[PATCH v4 1/4] ACPI: parse SPCR and enable matching console

[Aleksey Makarov]

Hi Andy, 

Thank you for review.

On 02/29/2016 04:29 PM, Andy Shevchenko wrote:
> On Mon, Feb 29, 2016 at 2:02 PM, Aleksey Makarov
> <aleksey.makarov@linaro.org> wrote:
>> 'ARM Server Base Boot Requiremets' [1] mentions SPCR (Serial Port
>> Console Redirection Table) [2] as a mandatory ACPI table that
>> specifies the configuration of serial console.
>>
>> Parse this table and check if any registered console match the
>> description.  If it does, enable that console.
>>
>> Introduce a new function acpi_console_check().  At the uart port
>> registration, this function checks if the ACPI SPCR table specifies
>> its argument of type struct uart_port to be a console
>> and if so calls add_preferred_console().
> 
>> +       if (ACPI_FAILURE(status)) {
>> +               pr_err("could not get the table\n");
> 
> Is it worse to have on error level? Is it possible to have firmware
> without this table? I think it would be a normal case for non-arm
> world.
> I'm also not sure if this message useful even on warn level.

I will delete the message in the next version, thank you.

>> +               return -ENOENT;
>> +       }
>> +
>> +       if (table->header.revision < 2) {
>> +               err = -EINVAL;
>> +               pr_err("wrong table version\n");
> 
> And this one quite good to have, indeed.
> 
>> + * acpi_console_check - Check if uart matches the console specified by SPCR.
>> + *
>> + * @uport:     uart port to check
>> + *
> 
> Since you use sections, you may add:
> + * Description:

According to kernel-doc-nano-HOWTO.txt "Description: " is optional.

>> + * This function checks if the ACPI SPCR table specifies @uport to be a console
>> + * and if so calls add_preferred_console()
>> + *
>> + * Return: a non-error value if the console matches.
> 
>> @@ -2654,8 +2655,17 @@ int uart_add_one_port(struct uart_driver *drv, struct uart_port *uport)
>>                 spin_lock_init(&uport->lock);
>>                 lockdep_set_class(&uport->lock, &port_lock_key);
>>         }
>> -       if (uport->cons && uport->dev)
>> -               of_console_check(uport->dev->of_node, uport->cons->name, uport->line);
>> +
>> +       /*
>> +        * Support both open FW and ACPI access to console definitions.
>> +        * Both of_console_check() and acpi_console_check() will call
>> +        * add_preferred_console() if a console definition is found.
>> +        */
>> +       if (uport->cons && uport->dev) {
>> +               if (!acpi_console_check(uport))
> 
> if (cond1) {
>  if (cond2) {
> ...
>  }
> }
> 
> is equivalent to
> if (cond1 && cond2) {
> ...
> }

It is, but it's a style decision.  I would prefer to leave it as is because it emphasizes that
after meeting some condition we first call acpi_console_check() and then of_console_check().

Thank you
Aleksey Makarov

> 
>> +                       of_console_check(uport->dev->of_node, uport->cons->name,
>> +                                        uport->line);
>> +       }
> 
> 
> 

[PATCH v4 0/4] ACPI: parse the SPCR table

[Peter Hurley]

It's customary to cc reviewers of your previous series.
Please review my comments to v3.

Regards,
Peter Hurley

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
> Console Redirection Table) [2] as a mandatory ACPI table that
> specifies the configuration of serial console.
> 
> Introduce a new function acpi_console_check().  At the uart port
> registration, this function checks if the ACPI SPCR table specifies
> its argument of type struct uart_port to be a console
> and if so calls add_preferred_console().
> 
> Use SPCR to tell if SBSA serial driver should use 32-bit access to registers.
> 
> Based on the work by Leif Lindholm [3]
> 
> Should be applied to next-20160229.
> 
> Tested on QEMU.  SPCR support is included in QEMU's ARM mach-virt
> since 2.4 release.
> 
> v4:
> - drop patch "ACPI: change __init to __ref for early_acpi_os_unmap_memory()"
>   ACPI developers work on a new API and asked not to do that.
>   Instead, use acpi_get_table_with_size()/early_acpi_os_unmap_memory() once
>   and cache the result. (Lv Zheng)
> - fix some style issues (Yury Norov)
> 
> v3:
> https://lkml.kernel.org/g/1455559532-8305-1-git-send-email-aleksey.makarov at linaro.org
> 
> Greg Kroah-Hartman did not like v2 so I have rewritten this patchset:
> 
> - drop acpi_match() member of struct console
> - drop implementations of this member for pl011 and 8250
> - drop the patch that renames some vars in printk.c as it is not needed anymore
> - drop patch that introduces system wide acpi_table_parse2().
>   Instead introduce a custom acpi_table_parse_spcr() in spcr.c
> 
> Instead of introducing a new match_acpi() member of struct console,
> this patchset introduces a new function acpi_console_check().
> This function is called when a new uart is registered at serial_core.c
> the same way OF code checks for console.  If the registered uart is the
> console specified by SPCR table, this function calls add_preferred_console()
> 
> The restrictions of this approach are:
> 
> - only serial consoles can be set up
> - only consoles specified by the memory/io address can be set up
>   (SPCR can specify devices by PCI id/PCI address)
> 
> v2:
> https://lkml.kernel.org/g/1455299022-11641-1-git-send-email-aleksey.makarov at linaro.org
> - don't use SPCR if user specified console in command line
> - fix initialization order of newcon->index = 0
> - rename some variables at printk.c (Joe Perches, Peter Hurley)
> - enable ACPI_SPCR_TABLE in a separate patch (Andy Shevchenko)
> - remove the retry loop for console registering (Peter Hurley).
>   Instead, obtain SPCR with acpi_get_table().  That works after
>   call to acpi_early_init() i. e. in any *_initcall()
> - describe design decision behind introducing acpi_match() (Peter Hurley)
> - fix compilation for x86 + ACPI (Graeme Gregory)
> - introduce DBG2 constants in a separate patch (Andy Shevchenko)
> - fix a typo in DBG2 constants (Andy Shevchenko)
> - add ACPI_DBG2_ARM_SBSA_32BIT constant (Christopher Covington)
> - add support for ACPI_DBG2_ARM_SBSA_* consoles (Christopher Covington)
> - add documentation for functions
> - add a patch that uses SPCR to find if SBSA serial driver should use 32-bit
>   accessor functions (Christopher Covington)
> - change __init to __ref for early_acpi_os_unmap_memory() in a separate patch
> - introduce acpi_table_parse2() in a separate patch
> - fix fetching the SPCR table early (Mark Salter)
> - add a patch from Mark Salter that introduces support for matching 8250-based
>   consoles
> 
> v1:
> https://lkml.kernel.org/g/1453722324-22407-1-git-send-email-aleksey.makarov at linaro.org
> 
> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
> [2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
> [3] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm at linaro.org
> 
> Aleksey Makarov (4):
>   ACPI: parse SPCR and enable matching console
>   ACPI: enable ACPI_SPCR_TABLE on ARM64
>   ACPI: add definitions of DBG2 subtypes
>   serial: pl011: use ACPI SPCR to setup 32-bit access
> 
>  arch/arm64/Kconfig               |   1 +
>  drivers/acpi/Kconfig             |   3 +
>  drivers/acpi/Makefile            |   1 +
>  drivers/acpi/spcr.c              | 138 +++++++++++++++++++++++++++++++++++++++
>  drivers/tty/serial/amba-pl011.c  |   2 +
>  drivers/tty/serial/serial_core.c |  14 +++-
>  include/acpi/actbl2.h            |   5 ++
>  include/linux/acpi.h             |  15 +++++
>  8 files changed, 177 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/acpi/spcr.c
> 

[PATCH v4 2/4] ACPI: enable ACPI_SPCR_TABLE on ARM64

[Peter Hurley]

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
> SBBR mentions SPCR as a mandatory ACPI table.
> So enable it for ARM64

Why is this opt-in per-arch?


> Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
> ---
>  arch/arm64/Kconfig | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
> index 9dc5209..544af2e 100644
> --- a/arch/arm64/Kconfig
> +++ b/arch/arm64/Kconfig
> @@ -3,6 +3,7 @@ config ARM64
>  	select ACPI_CCA_REQUIRED if ACPI
>  	select ACPI_GENERIC_GSI if ACPI
>  	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
> +	select ACPI_SPCR_TABLE if ACPI
>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>  	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>  	select ARCH_HAS_ELF_RANDOMIZE
> 

[PATCH v4 0/4] ACPI: parse the SPCR table

[Peter Hurley]

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
> Console Redirection Table) [2] as a mandatory ACPI table that
> specifies the configuration of serial console.
> 
> Introduce a new function acpi_console_check().  At the uart port
> registration, this function checks if the ACPI SPCR table specifies
> its argument of type struct uart_port to be a console
> and if so calls add_preferred_console().

How will a user enable an earlycon on the same console as the SPCR
console if there is no DBG2 table?


> Use SPCR to tell if SBSA serial driver should use 32-bit access to registers.
> 
> Based on the work by Leif Lindholm [3]
> 
> Should be applied to next-20160229.
> 
> Tested on QEMU.  SPCR support is included in QEMU's ARM mach-virt
> since 2.4 release.
> 
> v4:
> - drop patch "ACPI: change __init to __ref for early_acpi_os_unmap_memory()"
>   ACPI developers work on a new API and asked not to do that.
>   Instead, use acpi_get_table_with_size()/early_acpi_os_unmap_memory() once
>   and cache the result. (Lv Zheng)
> - fix some style issues (Yury Norov)
> 
> v3:
> https://lkml.kernel.org/g/1455559532-8305-1-git-send-email-aleksey.makarov at linaro.org
> 
> Greg Kroah-Hartman did not like v2 so I have rewritten this patchset:
> 
> - drop acpi_match() member of struct console
> - drop implementations of this member for pl011 and 8250
> - drop the patch that renames some vars in printk.c as it is not needed anymore
> - drop patch that introduces system wide acpi_table_parse2().
>   Instead introduce a custom acpi_table_parse_spcr() in spcr.c
> 
> Instead of introducing a new match_acpi() member of struct console,
> this patchset introduces a new function acpi_console_check().
> This function is called when a new uart is registered at serial_core.c
> the same way OF code checks for console.  If the registered uart is the
> console specified by SPCR table, this function calls add_preferred_console()
> 
> The restrictions of this approach are:
> 
> - only serial consoles can be set up
> - only consoles specified by the memory/io address can be set up
>   (SPCR can specify devices by PCI id/PCI address)
> 
> v2:
> https://lkml.kernel.org/g/1455299022-11641-1-git-send-email-aleksey.makarov at linaro.org
> - don't use SPCR if user specified console in command line
> - fix initialization order of newcon->index = 0
> - rename some variables at printk.c (Joe Perches, Peter Hurley)
> - enable ACPI_SPCR_TABLE in a separate patch (Andy Shevchenko)
> - remove the retry loop for console registering (Peter Hurley).
>   Instead, obtain SPCR with acpi_get_table().  That works after
>   call to acpi_early_init() i. e. in any *_initcall()
> - describe design decision behind introducing acpi_match() (Peter Hurley)
> - fix compilation for x86 + ACPI (Graeme Gregory)
> - introduce DBG2 constants in a separate patch (Andy Shevchenko)
> - fix a typo in DBG2 constants (Andy Shevchenko)
> - add ACPI_DBG2_ARM_SBSA_32BIT constant (Christopher Covington)
> - add support for ACPI_DBG2_ARM_SBSA_* consoles (Christopher Covington)
> - add documentation for functions
> - add a patch that uses SPCR to find if SBSA serial driver should use 32-bit
>   accessor functions (Christopher Covington)
> - change __init to __ref for early_acpi_os_unmap_memory() in a separate patch
> - introduce acpi_table_parse2() in a separate patch
> - fix fetching the SPCR table early (Mark Salter)
> - add a patch from Mark Salter that introduces support for matching 8250-based
>   consoles
> 
> v1:
> https://lkml.kernel.org/g/1453722324-22407-1-git-send-email-aleksey.makarov at linaro.org
> 
> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
> [2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
> [3] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm at linaro.org
> 
> Aleksey Makarov (4):
>   ACPI: parse SPCR and enable matching console
>   ACPI: enable ACPI_SPCR_TABLE on ARM64
>   ACPI: add definitions of DBG2 subtypes
>   serial: pl011: use ACPI SPCR to setup 32-bit access
> 
>  arch/arm64/Kconfig               |   1 +
>  drivers/acpi/Kconfig             |   3 +
>  drivers/acpi/Makefile            |   1 +
>  drivers/acpi/spcr.c              | 138 +++++++++++++++++++++++++++++++++++++++
>  drivers/tty/serial/amba-pl011.c  |   2 +
>  drivers/tty/serial/serial_core.c |  14 +++-
>  include/acpi/actbl2.h            |   5 ++
>  include/linux/acpi.h             |  15 +++++
>  8 files changed, 177 insertions(+), 2 deletions(-)
>  create mode 100644 drivers/acpi/spcr.c
> 

[PATCH v4 2/4] ACPI: enable ACPI_SPCR_TABLE on ARM64

[Aleksey Makarov]

On 03/01/2016 06:27 PM, Peter Hurley wrote:
> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>> SBBR mentions SPCR as a mandatory ACPI table.
>> So enable it for ARM64
> 
> Why is this opt-in per-arch?

It could depend only on CONFIG_ACPI.
I will do that in the next version, thank you

>> Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
>> ---
>>  arch/arm64/Kconfig | 1 +
>>  1 file changed, 1 insertion(+)
>>
>> diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
>> index 9dc5209..544af2e 100644
>> --- a/arch/arm64/Kconfig
>> +++ b/arch/arm64/Kconfig
>> @@ -3,6 +3,7 @@ config ARM64
>>  	select ACPI_CCA_REQUIRED if ACPI
>>  	select ACPI_GENERIC_GSI if ACPI
>>  	select ACPI_REDUCED_HARDWARE_ONLY if ACPI
>> +	select ACPI_SPCR_TABLE if ACPI
>>  	select ARCH_HAS_DEVMEM_IS_ALLOWED
>>  	select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
>>  	select ARCH_HAS_ELF_RANDOMIZE
>>
> 

[PATCH v4 0/4] ACPI: parse the SPCR table

[Aleksey Makarov]

On 03/01/2016 06:31 PM, Peter Hurley wrote:
> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>> Console Redirection Table) [2] as a mandatory ACPI table that
>> specifies the configuration of serial console.
>>
>> Introduce a new function acpi_console_check().  At the uart port
>> registration, this function checks if the ACPI SPCR table specifies
>> its argument of type struct uart_port to be a console
>> and if so calls add_preferred_console().
> 
> How will a user enable an earlycon on the same console as the SPCR
> console if there is no DBG2 table?

...
[    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
[    0.000000] bootconsole [pl11] enabled
...
[    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
...
[    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
[    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
[    0.319502] console [ttyAMA0] enabled
[    0.319502] console [ttyAMA0] enabled
[    0.319933] bootconsole [pl11] disabled
[    0.319933] bootconsole [pl11] disabled
...

Why?

> 
> 
>> Use SPCR to tell if SBSA serial driver should use 32-bit access to registers.
>>
>> Based on the work by Leif Lindholm [3]
>>
>> Should be applied to next-20160229.
>>
>> Tested on QEMU.  SPCR support is included in QEMU's ARM mach-virt
>> since 2.4 release.
>>
>> v4:
>> - drop patch "ACPI: change __init to __ref for early_acpi_os_unmap_memory()"
>>   ACPI developers work on a new API and asked not to do that.
>>   Instead, use acpi_get_table_with_size()/early_acpi_os_unmap_memory() once
>>   and cache the result. (Lv Zheng)
>> - fix some style issues (Yury Norov)
>>
>> v3:
>> https://lkml.kernel.org/g/1455559532-8305-1-git-send-email-aleksey.makarov at linaro.org
>>
>> Greg Kroah-Hartman did not like v2 so I have rewritten this patchset:
>>
>> - drop acpi_match() member of struct console
>> - drop implementations of this member for pl011 and 8250
>> - drop the patch that renames some vars in printk.c as it is not needed anymore
>> - drop patch that introduces system wide acpi_table_parse2().
>>   Instead introduce a custom acpi_table_parse_spcr() in spcr.c
>>
>> Instead of introducing a new match_acpi() member of struct console,
>> this patchset introduces a new function acpi_console_check().
>> This function is called when a new uart is registered at serial_core.c
>> the same way OF code checks for console.  If the registered uart is the
>> console specified by SPCR table, this function calls add_preferred_console()
>>
>> The restrictions of this approach are:
>>
>> - only serial consoles can be set up
>> - only consoles specified by the memory/io address can be set up
>>   (SPCR can specify devices by PCI id/PCI address)
>>
>> v2:
>> https://lkml.kernel.org/g/1455299022-11641-1-git-send-email-aleksey.makarov at linaro.org
>> - don't use SPCR if user specified console in command line
>> - fix initialization order of newcon->index = 0
>> - rename some variables at printk.c (Joe Perches, Peter Hurley)
>> - enable ACPI_SPCR_TABLE in a separate patch (Andy Shevchenko)
>> - remove the retry loop for console registering (Peter Hurley).
>>   Instead, obtain SPCR with acpi_get_table().  That works after
>>   call to acpi_early_init() i. e. in any *_initcall()
>> - describe design decision behind introducing acpi_match() (Peter Hurley)
>> - fix compilation for x86 + ACPI (Graeme Gregory)
>> - introduce DBG2 constants in a separate patch (Andy Shevchenko)
>> - fix a typo in DBG2 constants (Andy Shevchenko)
>> - add ACPI_DBG2_ARM_SBSA_32BIT constant (Christopher Covington)
>> - add support for ACPI_DBG2_ARM_SBSA_* consoles (Christopher Covington)
>> - add documentation for functions
>> - add a patch that uses SPCR to find if SBSA serial driver should use 32-bit
>>   accessor functions (Christopher Covington)
>> - change __init to __ref for early_acpi_os_unmap_memory() in a separate patch
>> - introduce acpi_table_parse2() in a separate patch
>> - fix fetching the SPCR table early (Mark Salter)
>> - add a patch from Mark Salter that introduces support for matching 8250-based
>>   consoles
>>
>> v1:
>> https://lkml.kernel.org/g/1453722324-22407-1-git-send-email-aleksey.makarov at linaro.org
>>
>> [1] http://infocenter.arm.com/help/index.jsp?topic=/com.arm.doc.den0044a/index.html
>> [2] https://msdn.microsoft.com/en-us/library/windows/hardware/dn639132(v=vs.85).aspx
>> [3] https://lkml.kernel.org/g/1441716217-23786-1-git-send-email-leif.lindholm at linaro.org
>>
>> Aleksey Makarov (4):
>>   ACPI: parse SPCR and enable matching console
>>   ACPI: enable ACPI_SPCR_TABLE on ARM64
>>   ACPI: add definitions of DBG2 subtypes
>>   serial: pl011: use ACPI SPCR to setup 32-bit access
>>
>>  arch/arm64/Kconfig               |   1 +
>>  drivers/acpi/Kconfig             |   3 +
>>  drivers/acpi/Makefile            |   1 +
>>  drivers/acpi/spcr.c              | 138 +++++++++++++++++++++++++++++++++++++++
>>  drivers/tty/serial/amba-pl011.c  |   2 +
>>  drivers/tty/serial/serial_core.c |  14 +++-
>>  include/acpi/actbl2.h            |   5 ++
>>  include/linux/acpi.h             |  15 +++++
>>  8 files changed, 177 insertions(+), 2 deletions(-)
>>  create mode 100644 drivers/acpi/spcr.c
>>
> 
> --
> To unsubscribe from this list: send the line "unsubscribe linux-acpi" in
> the body of a message to majordomo at vger.kernel.org
> More majordomo info at  http://vger.kernel.org/majordomo-info.html
> 

[PATCH v4 0/4] ACPI: parse the SPCR table

[Peter Hurley]

On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
> 
> 
> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>> specifies the configuration of serial console.
>>>
>>> Introduce a new function acpi_console_check().  At the uart port
>>> registration, this function checks if the ACPI SPCR table specifies
>>> its argument of type struct uart_port to be a console
>>> and if so calls add_preferred_console().
>>
>> How will a user enable an earlycon on the same console as the SPCR
>> console if there is no DBG2 table?
> 
> ...
> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
> [    0.000000] bootconsole [pl11] enabled
> ...
> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
> ...
> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
> [    0.319502] console [ttyAMA0] enabled
> [    0.319502] console [ttyAMA0] enabled
> [    0.319933] bootconsole [pl11] disabled
> [    0.319933] bootconsole [pl11] disabled
> ...
> 
> Why?

That's pretty disingenuous; via command line?

By that measure, none of your patches are required because a user
can already start both console and earlycon without them.

With the console location specified in the SPCR, earlycon should
be opt-in on the command-line simply with "earlycon" command-line
parameter.

[PATCH v4 0/4] ACPI: parse the SPCR table

[Aleksey Makarov]

On 03/03/2016 06:35 PM, Peter Hurley wrote:
> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>
>>
>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>> specifies the configuration of serial console.
>>>>
>>>> Introduce a new function acpi_console_check().  At the uart port
>>>> registration, this function checks if the ACPI SPCR table specifies
>>>> its argument of type struct uart_port to be a console
>>>> and if so calls add_preferred_console().
>>>
>>> How will a user enable an earlycon on the same console as the SPCR
>>> console if there is no DBG2 table?
>>
>> ...
>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>> [    0.000000] bootconsole [pl11] enabled
>> ...
>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>> ...
>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>> [    0.319502] console [ttyAMA0] enabled
>> [    0.319502] console [ttyAMA0] enabled
>> [    0.319933] bootconsole [pl11] disabled
>> [    0.319933] bootconsole [pl11] disabled
>> ...
>>
>> Why?
> 
> That's pretty disingenuous; via command line?
> 
> By that measure, none of your patches are required because a user
> can already start both console and earlycon without them.
> 
> With the console location specified in the SPCR, earlycon should
> be opt-in on the command-line simply with "earlycon" command-line
> parameter.

Yes.  That's why we have SPCR *and* DBG2. 
DBG2 specifies where we should run earlycon.

>>> How will a user enable an earlycon on the same console as the SPCR
>>> console if there is no DBG2 table?

In no way.  You need DBG2 to run earlycon.

(If you don't want to specify it's address etc explicitly)

[PATCH v4 0/4] ACPI: parse the SPCR table

[Peter Hurley]

On 03/04/2016 03:53 AM, Aleksey Makarov wrote:
> 
> 
> On 03/03/2016 06:35 PM, Peter Hurley wrote:
>> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>>
>>>
>>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>>> specifies the configuration of serial console.
>>>>>
>>>>> Introduce a new function acpi_console_check().  At the uart port
>>>>> registration, this function checks if the ACPI SPCR table specifies
>>>>> its argument of type struct uart_port to be a console
>>>>> and if so calls add_preferred_console().
>>>>
>>>> How will a user enable an earlycon on the same console as the SPCR
>>>> console if there is no DBG2 table?
>>>
>>> ...
>>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>>> [    0.000000] bootconsole [pl11] enabled
>>> ...
>>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>>> ...
>>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>>> [    0.319502] console [ttyAMA0] enabled
>>> [    0.319502] console [ttyAMA0] enabled
>>> [    0.319933] bootconsole [pl11] disabled
>>> [    0.319933] bootconsole [pl11] disabled
>>> ...
>>>
>>> Why?
>>
>> That's pretty disingenuous; via command line?
>>
>> By that measure, none of your patches are required because a user
>> can already start both console and earlycon without them.
>>
>> With the console location specified in the SPCR, earlycon should
>> be opt-in on the command-line simply with "earlycon" command-line
>> parameter.
> 
> Yes.  That's why we have SPCR *and* DBG2. 
> DBG2 specifies where we should run earlycon.
> 
>>>> How will a user enable an earlycon on the same console as the SPCR
>>>> console if there is no DBG2 table?
> 
> In no way.  You need DBG2 to run earlycon.

And that's an entirely arbitrary decision being made by you.
Which I think is unnecessarily limited.


> (If you don't want to specify it's address etc explicitly)

[PATCH v4 0/4] ACPI: parse the SPCR table

[Aleksey Makarov]

Hi Peter,

You are right, SPCR console should support earlycon.
I will send next version that will try to follow your recommendations in 
a week, after I return from vacations.

As we discussed with Christopher, "serial: pl011: use SPCR to setup 
32-bit access" will be dropped.

Thank you
Aleksey Makarov

On 04.03.2016 22:47, Peter Hurley wrote:
> On 03/04/2016 03:53 AM, Aleksey Makarov wrote:
>>
>>
>> On 03/03/2016 06:35 PM, Peter Hurley wrote:
>>> On 03/03/2016 03:59 AM, Aleksey Makarov wrote:
>>>>
>>>>
>>>> On 03/01/2016 06:31 PM, Peter Hurley wrote:
>>>>> On 02/29/2016 04:02 AM, Aleksey Makarov wrote:
>>>>>> 'ARM Server Base Boot Requirements' [1] mentions SPCR (Serial Port
>>>>>> Console Redirection Table) [2] as a mandatory ACPI table that
>>>>>> specifies the configuration of serial console.
>>>>>>
>>>>>> Introduce a new function acpi_console_check().  At the uart port
>>>>>> registration, this function checks if the ACPI SPCR table specifies
>>>>>> its argument of type struct uart_port to be a console
>>>>>> and if so calls add_preferred_console().
>>>>>
>>>>> How will a user enable an earlycon on the same console as the SPCR
>>>>> console if there is no DBG2 table?
>>>>
>>>> ...
>>>> [    0.000000] earlycon: pl11 at MMIO 0x0000000009000000 (options '')
>>>> [    0.000000] bootconsole [pl11] enabled
>>>> ...
>>>> [    0.000000] Kernel command line:  root=/dev/vda1 rw systemd.show_status=no acpi=force earlycon=pl011,0x9000000
>>>> ...
>>>> [    0.318248] ACPI: SPCR: adding preferred console [ttyAMA0]
>>>> [    0.318736] ARMH0011:00: ttyAMA0 at MMIO 0x9000000 (irq = 5, base_baud = 0) is a SBSA
>>>> [    0.319502] console [ttyAMA0] enabled
>>>> [    0.319502] console [ttyAMA0] enabled
>>>> [    0.319933] bootconsole [pl11] disabled
>>>> [    0.319933] bootconsole [pl11] disabled
>>>> ...
>>>>
>>>> Why?
>>>
>>> That's pretty disingenuous; via command line?
>>>
>>> By that measure, none of your patches are required because a user
>>> can already start both console and earlycon without them.
>>>
>>> With the console location specified in the SPCR, earlycon should
>>> be opt-in on the command-line simply with "earlycon" command-line
>>> parameter.
>>
>> Yes.  That's why we have SPCR *and* DBG2.
>> DBG2 specifies where we should run earlycon.
>>
>>>>> How will a user enable an earlycon on the same console as the SPCR
>>>>> console if there is no DBG2 table?
>>
>> In no way.  You need DBG2 to run earlycon.
>
> And that's an entirely arbitrary decision being made by you.
> Which I think is unnecessarily limited.
>
>
>> (If you don't want to specify it's address etc explicitly)
>
>

[PATCH v4 2/4] ACPI: enable ACPI_SPCR_TABLE on ARM64

[Timur Tabi]

On Mon, Feb 29, 2016 at 6:02 AM, Aleksey Makarov
<aleksey.makarov@linaro.org> wrote:
> SBBR mentions SPCR as a mandatory ACPI table.
> So enable it for ARM64
>
> Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>

Tested-by: Timur Tabi <timur@codeaurora.org>

I know another version of patch is coming, but I tested this version
and it works.