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authorAleksey Makarov <aleksey.makarov@linaro.org>2016-09-27 23:54:13 +0300
committerGreg Kroah-Hartman <gregkh@linuxfoundation.org>2016-09-28 17:46:46 +0200
commitad1696f6f09daacfdf2bf04bc83cd8f48d80e34a (patch)
tree5621bb984dfcd615ce17180fd00f08d8163eb756 /drivers/tty
parentd503187b6cc4e41c21c02e695e0e7b5acdd066de (diff)
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: 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>
Diffstat (limited to 'drivers/tty')
-rw-r--r--drivers/tty/serial/earlycon.c19
1 files changed, 17 insertions, 2 deletions
diff --git a/drivers/tty/serial/earlycon.c b/drivers/tty/serial/earlycon.c
index 836cad222fcc..c3651540e1ba 100644
--- a/drivers/tty/serial/earlycon.c
+++ b/drivers/tty/serial/earlycon.c
@@ -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)