RISC-V: ACPI: Enable SPCR table for console output on RISC-V

The ACPI SPCR code has been used to enable console output for ARM64 and
X86. The same code can be reused for RISC-V. Furthermore, SPCR table is
mandated for headless system as outlined in the RISC-V BRS
Specification, chapter 6.

Signed-off-by: Sia Jee Heng <jeeheng.sia@starfivetech.com>
Reviewed-by: Sunil V L <sunilvl@ventanamicro.com>
Link: https://lore.kernel.org/r/20240502073751.102093-2-jeeheng.sia@starfivetech.com
Signed-off-by: Palmer Dabbelt <palmer@rivosinc.com>

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index b94176e25be1810e749cb94686b9c536fd9a2bb0..287c17daa9d514018e468afdc89a20012dcda1ae 100644 (file)
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -14,6 +14,7 @@ config RISCV
        def_bool y
        select ACPI_GENERIC_GSI if ACPI
        select ACPI_REDUCED_HARDWARE_ONLY if ACPI
+       select ACPI_SPCR_TABLE if ACPI
        select ARCH_DMA_DEFAULT_COHERENT
        select ARCH_ENABLE_HUGEPAGE_MIGRATION if HUGETLB_PAGE && MIGRATION
        select ARCH_ENABLE_SPLIT_PMD_PTLOCK if PGTABLE_LEVELS > 2

diff --git a/arch/riscv/kernel/acpi.c b/arch/riscv/kernel/acpi.c
index e619edc8b0cc972c1a83809c9f0ebeb10c3331a6..43a12c00ae8b1f6e0e426e96fa9691346b6ab782 100644 (file)
--- a/arch/riscv/kernel/acpi.c
+++ b/arch/riscv/kernel/acpi.c
@@ -17,7 +17,9 @@
 #include <linux/efi.h>
 #include <linux/io.h>
 #include <linux/memblock.h>
+#include <linux/of_fdt.h>
 #include <linux/pci.h>
+#include <linux/serial_core.h>
 
 int acpi_noirq = 1;            /* skip ACPI IRQ initialization */
 int acpi_disabled = 1;
@@ -131,7 +133,7 @@ void __init acpi_boot_table_init(void)
        if (param_acpi_off ||
            (!param_acpi_on && !param_acpi_force &&
             efi.acpi20 == EFI_INVALID_TABLE_ADDR))
-               return;
+               goto done;
 
        /*
         * ACPI is disabled at this point. Enable it in order to parse
@@ -151,6 +153,14 @@ void __init acpi_boot_table_init(void)
                if (!param_acpi_force)
                        disable_acpi();
        }
+
+done:
+       if (acpi_disabled) {
+               if (earlycon_acpi_spcr_enable)
+                       early_init_dt_scan_chosen_stdout();
+       } else {
+               acpi_parse_spcr(earlycon_acpi_spcr_enable, true);
+       }
 }
 
 static int acpi_parse_madt_rintc(union acpi_subtable_headers *header, const unsigned long end)