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Commit ad1696f6 authored by Aleksey Makarov's avatar Aleksey Makarov Committed by Greg Kroah-Hartman
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ACPI: parse SPCR and enable matching console 

'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.

Defer initialization of DT earlycon until ACPI/DT decision is made.

Parse the ACPI SPCR table, setup earlycon if required,
enable specified console.

Thanks to Peter Hurley for explaining how this should work.

[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



Signed-off-by: default avatarAleksey Makarov <aleksey.makarov@linaro.org>
Acked-by: default avatarRafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: default avatarPeter Hurley <peter@hurleysoftware.com>
Tested-by: default avatarKefeng Wang <wangkefeng.wang@huawei.com>
Tested-by: default avatarChristopher Covington <cov@codeaurora.org>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent d503187b

drivers/acpi/Kconfig

+3 −0
Original line number Diff line number Diff line
@@ -77,6 +77,9 @@ config ACPI_DEBUGGER_USER 


endif



config ACPI_SPCR_TABLE

	bool



config ACPI_SLEEP

	bool

	depends on SUSPEND || HIBERNATION

drivers/acpi/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -81,6 +81,7 @@ 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

drivers/acpi/spcr.c

0 → 100644
+111 −0
Original line number Diff line number Diff line 
/*

 * 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>



/**

 * parse_spcr() - parse ACPI SPCR table and add preferred console

 *

 * @earlycon: set up earlycon for the console specified by the table

 *

 * For the architectures with support for ACPI, CONFIG_ACPI_SPCR_TABLE may be

 * defined to parse ACPI SPCR table.  As a result of the parsing preferred

 * console is registered and if @earlycon is true, earlycon is set up.

 *

 * When CONFIG_ACPI_SPCR_TABLE is defined, this function should be called

 * from arch inintialization code as soon as the DT/ACPI decision is made.

 *

 */

int __init parse_spcr(bool earlycon)

{

	static char opts[64];

	struct acpi_table_spcr *table;

	acpi_size table_size;

	acpi_status status;

	char *uart;

	char *iotype;

	int baud_rate;

	int err;



	if (acpi_disabled)

		return -ENODEV;



	status = acpi_get_table_with_size(ACPI_SIG_SPCR, 0,

					  (struct acpi_table_header **)&table,

					  &table_size);



	if (ACPI_FAILURE(status))

		return -ENOENT;



	if (table->header.revision < 2) {

		err = -ENOENT;

		pr_err("wrong table version\n");

		goto done;

	}



	iotype = table->serial_port.space_id == ACPI_ADR_SPACE_SYSTEM_MEMORY ?

			"mmio" : "io";



	switch (table->interface_type) {

	case ACPI_DBG2_ARM_SBSA_32BIT:

		iotype = "mmio32";

		/* fall through */

	case ACPI_DBG2_ARM_PL011:

	case ACPI_DBG2_ARM_SBSA_GENERIC:

	case ACPI_DBG2_BCM2835:

		uart = "pl011";

		break;

	case ACPI_DBG2_16550_COMPATIBLE:

	case ACPI_DBG2_16550_SUBSET:

		uart = "uart";

		break;

	default:

		err = -ENOENT;

		goto done;

	}



	switch (table->baud_rate) {

	case 3:

		baud_rate = 9600;

		break;

	case 4:

		baud_rate = 19200;

		break;

	case 6:

		baud_rate = 57600;

		break;

	case 7:

		baud_rate = 115200;

		break;

	default:

		err = -ENOENT;

		goto done;

	}



	snprintf(opts, sizeof(opts), "%s,%s,0x%llx,%d", uart, iotype,

		 table->serial_port.address, baud_rate);



	pr_info("console: %s\n", opts);



	if (earlycon)

		setup_earlycon(opts);



	err = add_preferred_console(uart, 0, opts + strlen(uart) + 1);



done:

	early_acpi_os_unmap_memory((void __iomem *)table, table_size);

	return err;

}

drivers/tty/serial/earlycon.c

+17 −2
Original line number Diff line number Diff line
@@ -21,6 +21,7 @@ 
#include <linux/sizes.h>

#include <linux/of.h>

#include <linux/of_fdt.h>

#include <linux/acpi.h>



#ifdef CONFIG_FIX_EARLYCON_MEM

#include <asm/fixmap.h>
@@ -198,6 +199,14 @@ int __init setup_earlycon(char *buf) 
	return -ENOENT;

}



/*

 * When CONFIG_ACPI_SPCR_TABLE is defined, "earlycon" without parameters in

 * command line does not start DT earlycon immediately, instead it defers

 * starting it until DT/ACPI decision is made.  At that time if ACPI is enabled

 * call parse_spcr(), else call early_init_dt_scan_chosen_stdout()

 */

bool earlycon_init_is_deferred __initdata;



/* early_param wrapper for setup_earlycon() */

static int __init param_setup_earlycon(char *buf)

{
@@ -207,8 +216,14 @@ static int __init param_setup_earlycon(char *buf) 
	 * Just 'earlycon' is a valid param for devicetree earlycons;

	 * don't generate a warning from parse_early_params() in that case

	 */

	if (!buf || !buf[0])

	if (!buf || !buf[0]) {

		if (IS_ENABLED(CONFIG_ACPI_SPCR_TABLE)) {

			earlycon_init_is_deferred = true;

			return 0;

		} else {

			return early_init_dt_scan_chosen_stdout();

		}

	}



	err = setup_earlycon(buf);

	if (err == -ENOENT || err == -EALREADY)

include/linux/acpi.h

+6 −0
Original line number Diff line number Diff line
@@ -1074,4 +1074,10 @@ void acpi_table_upgrade(void); 
static inline void acpi_table_upgrade(void) { }

#endif



#ifdef CONFIG_ACPI_SPCR_TABLE

int parse_spcr(bool earlycon);

#else

static inline int parse_spcr(bool earlycon) { return 0; }

#endif



#endif	/*_LINUX_ACPI_H*/