ARM64: ACPI: enable ACPI_SPCR_TABLE

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

Earlycon should be set up as early as possible.  ACPI boot tables are
mapped in arch/arm64/kernel/acpi.c:acpi_boot_table_init() that
is called from setup_arch() and that's where we parse SPCR.
So it has to be opted-in per-arch.

When ACPI_SPCR_TABLE is defined initialization of DT earlycon is
deferred until the DT/ACPI decision is done.  Initialize DT earlycon
if ACPI is disabled.

Acked-by: Will Deacon <will.deacon@arm.com>
Acked-by: Hanjun Guo <hanjun.guo@linaro.org>
Signed-off-by: Aleksey Makarov <aleksey.makarov@linaro.org>
Tested-by: Kefeng Wang <wangkefeng.wang@huawei.com>
Tested-by: Christopher Covington <cov@codeaurora.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

2 files changed, 11 insertions, 1 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index bc3f00f586f1..11a2d36b27ef 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -4,6 +4,7 @@ config ARM64
         select ACPI_GENERIC_GSI if ACPI
         select ACPI_REDUCED_HARDWARE_ONLY if ACPI
         select ACPI_MCFG if ACPI
+        select ACPI_SPCR_TABLE if ACPI
         select ARCH_HAS_DEVMEM_IS_ALLOWED
         select ARCH_HAS_ACPI_TABLE_UPGRADE if ACPI
         select ARCH_HAS_ATOMIC64_DEC_IF_POSITIVE
diff --git a/arch/arm64/kernel/acpi.c b/arch/arm64/kernel/acpi.c
index 3e4f1a45b125..252a6d9c1da5 100644
--- a/arch/arm64/kernel/acpi.c
+++ b/arch/arm64/kernel/acpi.c
@@ -24,6 +24,7 @@
 #include <linux/memblock.h>
 #include <linux/of_fdt.h>
 #include <linux/smp.h>
+#include <linux/serial_core.h>
 
 #include <asm/cputype.h>
 #include <asm/cpu_ops.h>
@@ -206,7 +207,7 @@ void __init acpi_boot_table_init(void)
         if (param_acpi_off ||
             (!param_acpi_on && !param_acpi_force &&
              of_scan_flat_dt(dt_scan_depth1_nodes, NULL)))
-                return;
+                goto done;
 
         /*
          * ACPI is disabled at this point. Enable it in order to parse
@@ -226,6 +227,14 @@ void __init acpi_boot_table_init(void)
                 if (!param_acpi_force)
                         disable_acpi();
         }
+
+done:
+        if (acpi_disabled) {
+                if (earlycon_init_is_deferred)
+                        early_init_dt_scan_chosen_stdout();
+        } else {
+                parse_spcr(earlycon_init_is_deferred);
+        }
 }
 
 #ifdef CONFIG_ACPI_APEI