[PATCH RFC v4 17/18] ACPI: RISC-V: Add support for RISC-V Quality of Service Controller (RQSC)

[Drew Fustini]

Call acpi_parse_rqsc() from acpi_arch_init() to discover CBQRI
controllers when an RQSC table is present.

Gate on CONFIG_RISCV_CBQRI_DRIVER rather than CONFIG_RISCV_ISA_SSQOSID
so a kernel built with the ISA extension but without the driver (e.g.
RESCTRL_FS=n) does not walk the table and print a misleading "found 0
CBQRI controllers" line on every boot.

Link: https://github.com/riscv-non-isa/riscv-cbqri/releases/tag/v1.0
Link: https://github.com/riscv-non-isa/riscv-rqsc/blob/main/src/
Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Drew Fustini <fustini at kernel.org>
---
 drivers/acpi/riscv/init.c | 21 +++++++++++++++++++++
 1 file changed, 21 insertions(+)

diff --git a/drivers/acpi/riscv/init.c b/drivers/acpi/riscv/init.c
index 7c00f7995e86..129ebfae28be 100644
--- a/drivers/acpi/riscv/init.c
+++ b/drivers/acpi/riscv/init.c
@@ -5,11 +5,32 @@
  */
 
 #include <linux/acpi.h>
+#include <linux/cleanup.h>
 #include "init.h"
+#include "rqsc.h"
 
 void __init acpi_arch_init(void)
 {
 	riscv_acpi_init_gsi_mapping();
+
 	if (IS_ENABLED(CONFIG_ACPI_RIMT))
 		riscv_acpi_rimt_init();
+
+	if (IS_ENABLED(CONFIG_RISCV_CBQRI_DRIVER)) {
+		struct acpi_table_header *rqsc __free(acpi_put_table) = NULL;
+		acpi_status status = acpi_get_table(ACPI_SIG_RQSC, 0, &rqsc);
+
+		if (status == AE_NOT_FOUND) {
+			/* RQSC is optional. Silence on systems without it. */
+		} else if (ACPI_FAILURE(status)) {
+			pr_err("RQSC: failed to get table: %s\n",
+			       acpi_format_exception(status));
+		} else {
+			int rc = acpi_parse_rqsc(rqsc);
+
+			if (rc < 0)
+				pr_err("RQSC: failed to parse table: %d\n",
+				       rc);
+		}
+	}
 }

-- 
2.43.0