[kvm-unit-tests PATCH 3/7] riscv: Add ACPI support for timer frequency discovery

[Xiang W]

When a DT is not provided, read the system time base frequency from
the RHCT instead of aborting in timer_get_frequency().

RHCT Time Base Frequency is the ACPI equivalent of the DT
/cpus timebase-frequency property and is the same for all harts.
Keep DT as the preferred path when one is available.

Signed-off-by: Xiang W <wangxiang at iscas.ac.cn>
---
 lib/acpi.h        |  9 +++++++++
 lib/riscv/timer.c | 37 +++++++++++++++++++++++++------------
 2 files changed, 34 insertions(+), 12 deletions(-)

diff --git a/lib/acpi.h b/lib/acpi.h
index a905807d..2597e8ce 100644
--- a/lib/acpi.h
+++ b/lib/acpi.h
@@ -20,6 +20,7 @@
 #define MADT_SIGNATURE ACPI_SIGNATURE('A','P','I','C')
 #define SPCR_SIGNATURE ACPI_SIGNATURE('S','P','C','R')
 #define GTDT_SIGNATURE ACPI_SIGNATURE('G','T','D','T')
+#define RHCT_SIGNATURE ACPI_SIGNATURE('R','H','C','T')
 
 #define ACPI_SIGNATURE_8BYTE(c1, c2, c3, c4, c5, c6, c7, c8) \
 	(((uint64_t)(ACPI_SIGNATURE(c1, c2, c3, c4))) |	     \
@@ -328,6 +329,14 @@ struct acpi_table_gtdt {
 	u32 virtual_el2_timer_flags;
 };
 
+struct acpi_table_rhct {
+	ACPI_TABLE_HEADER_DEF
+	u32 flags;
+	u64 timebase_frequency;
+	u32 node_count;
+	u32 node_offset;
+};
+
 /* Reset to default packing */
 #pragma pack()
 
diff --git a/lib/riscv/timer.c b/lib/riscv/timer.c
index 18063b7e..2a18f0e0 100644
--- a/lib/riscv/timer.c
+++ b/lib/riscv/timer.c
@@ -13,24 +13,37 @@
 #include <asm/smp.h>
 #include <asm/timer.h>
 
+#ifdef CONFIG_EFI
+#include <acpi.h>
+#endif
+
 void timer_get_frequency(void)
 {
-	const struct fdt_property *prop;
-	u32 *data;
-	int cpus, len;
-
-	assert_msg(dt_available(), "ACPI not yet supported");
+	if (dt_available()) {
+		const struct fdt_property *prop;
+		u32 *data;
+		int cpus, len;
 
-	const void *fdt = dt_fdt();
+		const void *fdt = dt_fdt();
 
-	cpus = fdt_path_offset(fdt, "/cpus");
-	assert(cpus >= 0);
+		cpus = fdt_path_offset(fdt, "/cpus");
+		assert(cpus >= 0);
 
-	prop = fdt_get_property(fdt, cpus, "timebase-frequency", &len);
-	assert(prop != NULL && len == 4);
+		prop = fdt_get_property(fdt, cpus, "timebase-frequency", &len);
+		assert(prop != NULL && len == 4);
 
-	data = (u32 *)prop->data;
-	timebase_frequency = fdt32_to_cpu(*data);
+		data = (u32 *)prop->data;
+		timebase_frequency = fdt32_to_cpu(*data);
+	} else {
+#ifdef CONFIG_EFI
+		struct acpi_table_rhct *rhct;
+		rhct = find_acpi_table_addr(RHCT_SIGNATURE);
+		assert_msg(rhct, "Cannot find ACPI RHCT");
+		timebase_frequency = rhct->timebase_frequency;
+#else
+		assert_msg(false, "ACPI not available");
+#endif
+	}
 }
 
 void timer_start(unsigned long duration_us)
-- 
2.47.3