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

'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

'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 <redacted>
---
 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

On Mon, Feb 29, 2016 at 2:02 PM, Aleksey Makarov
[off-list ref] 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.

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

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
[off-list ref] wrote:

quoted

'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().

quoted

+       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.

quoted

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

And this one quite good to have, indeed.

quoted

+ * 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.

quoted

+ * 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.

quoted

@@ -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

quoted

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

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

Signed-off-by: Aleksey Makarov <redacted>
---
 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

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?

On 03/01/2016 06:27 PM, Peter Hurley wrote:

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

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

quoted

Signed-off-by: Aleksey Makarov <redacted>
---
 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

On Mon, Feb 29, 2016 at 6:02 AM, Aleksey Makarov
[off-list ref] wrote:

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

Signed-off-by: Aleksey Makarov <redacted>

Tested-by: Timur Tabi <redacted>

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

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 <redacted>
---
 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

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 <redacted>
---
 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

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

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

On 03/01/2016 06:31 PM, Peter Hurley wrote:

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'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?

quoted

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

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On 03/03/2016 03:59 AM, Aleksey Makarov wrote:

On 03/01/2016 06:31 PM, Peter Hurley wrote:

quoted

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'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.

On 03/03/2016 06:35 PM, Peter Hurley wrote:

On 03/03/2016 03:59 AM, Aleksey Makarov wrote:

quoted

On 03/01/2016 06:31 PM, Peter Hurley wrote:

quoted

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'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.

quoted

quoted

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)

On 03/04/2016 03:53 AM, Aleksey Makarov wrote:

On 03/03/2016 06:35 PM, Peter Hurley wrote:

quoted

On 03/03/2016 03:59 AM, Aleksey Makarov wrote:

quoted

On 03/01/2016 06:31 PM, Peter Hurley wrote:

quoted

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'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.

quoted

quoted

quoted

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)

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:

quoted

On 03/03/2016 06:35 PM, Peter Hurley wrote:

quoted

On 03/03/2016 03:59 AM, Aleksey Makarov wrote:

quoted

On 03/01/2016 06:31 PM, Peter Hurley wrote:

quoted

On 02/29/2016 04:02 AM, Aleksey Makarov wrote:

quoted

'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.

quoted

quoted

quoted

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.

quoted

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