[PATCH 17/24] ACPI: RISC-V: drivers/acpi: Add RHCT related code

[Sunil V L <sunilvl@ventanamicro.com>]

RHCT is a new table defined for RISC-V to communicate the
features of the CPU to the OS. Create a new architecture folder
in drivers/acpi and add RHCT parsing code.

Signed-off-by: Sunil V L <sunilvl@ventanamicro.com>
---
 arch/riscv/include/asm/acpi.h |  5 ++
 drivers/acpi/Makefile         |  2 +
 drivers/acpi/riscv/Makefile   |  2 +
 drivers/acpi/riscv/rhct.c     | 93 +++++++++++++++++++++++++++++++++++
 4 files changed, 102 insertions(+)
 create mode 100644 drivers/acpi/riscv/Makefile
 create mode 100644 drivers/acpi/riscv/rhct.c

diff --git a/arch/riscv/include/asm/acpi.h b/arch/riscv/include/asm/acpi.h
index 69a880b7257a..4fec9ea3b874 100644
--- a/arch/riscv/include/asm/acpi.h
+++ b/arch/riscv/include/asm/acpi.h
@@ -71,11 +71,16 @@ static inline u32 get_acpi_id_for_cpu(int cpu)
 {
 	return	acpi_cpu_get_madt_rintc(cpu)->uid;
 }
+int acpi_get_riscv_isa(struct acpi_table_header *table, unsigned int cpu, const char **isa);
 #else
 static inline u32 get_acpi_id_for_cpu(int cpu)
 {
 	return -1;
 }
+int acpi_get_riscv_isa(struct acpi_table_header *table, unsigned int cpu, const char **isa)
+{
+	return -1;
+}
 
 #endif /* CONFIG_ACPI */
 
diff --git a/drivers/acpi/Makefile b/drivers/acpi/Makefile
index feb36c0b9446..3fc5a0d54f6e 100644
--- a/drivers/acpi/Makefile
+++ b/drivers/acpi/Makefile
@@ -131,3 +131,5 @@ obj-y				+= dptf/
 obj-$(CONFIG_ARM64)		+= arm64/
 
 obj-$(CONFIG_ACPI_VIOT)		+= viot.o
+
+obj-$(CONFIG_RISCV)		+= riscv/
diff --git a/drivers/acpi/riscv/Makefile b/drivers/acpi/riscv/Makefile
new file mode 100644
index 000000000000..8b3b126e0b94
--- /dev/null
+++ b/drivers/acpi/riscv/Makefile
@@ -0,0 +1,2 @@
+# SPDX-License-Identifier: GPL-2.0-only
+obj-y 	+= rhct.o
diff --git a/drivers/acpi/riscv/rhct.c b/drivers/acpi/riscv/rhct.c
new file mode 100644
index 000000000000..7c64be64d9d9
--- /dev/null
+++ b/drivers/acpi/riscv/rhct.c
@@ -0,0 +1,93 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2022-2023, Ventana Micro Systems Inc
+ *	Author: Sunil V L <sunilvl@ventanamicro.com>
+ *
+ */
+
+#define pr_fmt(fmt)	"ACPI: RHCT: " fmt
+
+#include <linux/acpi.h>
+
+static void acpi_rhct_warn_missing(void)
+{
+	pr_warn_once("No RHCT table found\n");
+}
+
+static struct acpi_table_header *acpi_get_rhct(void)
+{
+	static struct acpi_table_header *rhct;
+	acpi_status status;
+
+	/*
+	 * RHCT will be used at runtime on every CPU, so we
+	 * don't need to call acpi_put_table() to release the table mapping.
+	 */
+	if (!rhct) {
+		status = acpi_get_table(ACPI_SIG_RHCT, 0, &rhct);
+		if (ACPI_FAILURE(status))
+			acpi_rhct_warn_missing();
+	}
+
+	return rhct;
+}
+
+/*
+ * During early boot, the caller should call acpi_get_table() and pass its pointer to
+ * these functions(and free up later). At run time, since this table can be used
+ * multiple times, pass NULL so that the table remains in memory
+ */
+int acpi_get_riscv_isa(struct acpi_table_header *table, unsigned int acpi_cpu_id, const char **isa)
+{
+	struct acpi_rhct_node_header *node, *ref_node, *end;
+	struct acpi_table_rhct *rhct;
+	struct acpi_rhct_hart_info *hart_info;
+	struct acpi_rhct_isa_string *isa_node;
+	u32 *hart_info_node_offset;
+	int i, j;
+
+	if (acpi_disabled) {
+		pr_debug("%s: acpi is disabled\n", __func__);
+		return -1;
+	}
+
+	if (!table) {
+		rhct = (struct acpi_table_rhct *)acpi_get_rhct();
+		if (!rhct)
+			return -ENOENT;
+	} else {
+		rhct = (struct acpi_table_rhct *)table;
+	}
+
+	node = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->node_offset);
+	end = ACPI_ADD_PTR(struct acpi_rhct_node_header, rhct, rhct->header.length);
+
+	for (i = 0; i < rhct->node_count; i++) {
+		if (node >= end)
+			break;
+		switch (node->type) {
+		case ACPI_RHCT_NODE_TYPE_HART_INFO:
+			hart_info = ACPI_ADD_PTR(struct acpi_rhct_hart_info, node,
+					sizeof(struct acpi_rhct_node_header));
+			hart_info_node_offset = ACPI_ADD_PTR(u32, hart_info,
+					sizeof(struct acpi_rhct_hart_info));
+			if (acpi_cpu_id != hart_info->uid)
+				break;
+			for (j = 0; j < hart_info->num_offsets; j++) {
+				ref_node = ACPI_ADD_PTR(struct acpi_rhct_node_header,
+						rhct, hart_info_node_offset[j]);
+				if (ref_node->type == ACPI_RHCT_NODE_TYPE_ISA_STRING) {
+					isa_node = ACPI_ADD_PTR(struct acpi_rhct_isa_string,
+							ref_node,
+							sizeof(struct acpi_rhct_node_header));
+					*isa = isa_node->isa;
+					return 0;
+				}
+			}
+			break;
+		}
+		node = ACPI_ADD_PTR(struct acpi_rhct_node_header, node, node->length);
+	}
+
+	return -1;
+}
-- 
2.38.0