[PATCH v2 1/1] RISC-V: ACPI: Enable SPCR table for console output on RISC-V

Sia Jee Heng
2024-05-02T07:38:22Z

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>
---
arch/riscv/Kconfig | 1 +
arch/riscv/kernel/acpi.c | 12 +++++++++++-
2 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index be09c8836d56..ff2e270bbe01 100644
--- 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 e619edc8b0cc..43a12c00ae8b 100644
--- 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)
--
2.34.1