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ACPI: parse SPCR and enable matching console

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'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: Aleksey Makarov <aleksey.makarov@linaro.org>
Acked-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Reviewed-by: Peter Hurley <peter@hurleysoftware.com>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Tested-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Aleksey Makarov
2016-09-27 23:54:13 +03:00
committed by Greg Kroah-Hartman
parent d503187b6c
commit ad1696f6f0
6 changed files with 146 additions and 3 deletions
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19
drivers/tty/serial/earlycon.c
View File

@@ -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])
return early_init_dt_scan_chosen_stdout();
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)