[PATCH v4 12/30] arm64: Add support for setting up the PSCI conduit through ACPI

[Nikos Nikoleris <nikos.nikoleris@arm.com>]

In systems with ACPI support and when a DT is not provided, we can use
the FADT to discover whether PSCI calls need to use smc or hvc
calls. This change implements this but retains the default behavior;
we check if a valid DT is provided, if not, we try to setup the PSCI
conduit using ACPI.

Signed-off-by: Nikos Nikoleris <nikos.nikoleris@arm.com>
Reviewed-by: Andrew Jones <drjones@redhat.com>
Reviewed-by: Ricardo Koller <ricarkol@google.com>
---
 arm/Makefile.arm64 |  4 ++++
 lib/acpi.h         |  5 +++++
 lib/arm/psci.c     | 37 ++++++++++++++++++++++++++++++++++++-
 3 files changed, 45 insertions(+), 1 deletion(-)

diff --git a/arm/Makefile.arm64 b/arm/Makefile.arm64
index 42e18e77..6dff6cad 100644
--- a/arm/Makefile.arm64
+++ b/arm/Makefile.arm64
@@ -25,6 +25,10 @@ cflatobjs += lib/arm64/processor.o
 cflatobjs += lib/arm64/spinlock.o
 cflatobjs += lib/arm64/gic-v3-its.o lib/arm64/gic-v3-its-cmd.o
 
+ifeq ($(CONFIG_EFI),y)
+cflatobjs += lib/acpi.o
+endif
+
 OBJDIRS += lib/arm64
 
 # arm64 specific tests
diff --git a/lib/acpi.h b/lib/acpi.h
index 38b6d5c9..5ba6e29d 100644
--- a/lib/acpi.h
+++ b/lib/acpi.h
@@ -129,6 +129,11 @@ struct acpi_table_fadt {
 	u64 hypervisor_id;	/* Hypervisor Vendor ID (ACPI 6.0) */
 };
 
+/* Masks for FADT ARM Boot Architecture Flags (arm_boot_flags) ACPI 5.1 */
+
+#define ACPI_FADT_PSCI_COMPLIANT    (1)	/* 00: [V5+] PSCI 0.2+ is implemented */
+#define ACPI_FADT_PSCI_USE_HVC      (1<<1)	/* 01: [V5+] HVC must be used instead of SMC as the PSCI conduit */
+
 struct acpi_table_facs_rev1 {
 	u32 signature;		/* ACPI Signature */
 	u32 length;		/* Length of structure, in bytes */
diff --git a/lib/arm/psci.c b/lib/arm/psci.c
index 9c031a12..bddb0787 100644
--- a/lib/arm/psci.c
+++ b/lib/arm/psci.c
@@ -56,7 +56,7 @@ void psci_system_off(void)
 	printf("CPU%d unable to do system off (error = %d)\n", smp_processor_id(), err);
 }
 
-void psci_set_conduit(void)
+static void psci_set_conduit_fdt(void)
 {
 	const void *fdt = dt_fdt();
 	const struct fdt_property *method;
@@ -75,3 +75,38 @@ void psci_set_conduit(void)
 	else
 		assert_msg(false, "Unknown PSCI conduit: %s", method->data);
 }
+
+#ifdef CONFIG_EFI
+
+#include <acpi.h>
+
+static void psci_set_conduit_acpi(void)
+{
+	struct acpi_table_fadt *fadt = find_acpi_table_addr(FACP_SIGNATURE);
+
+	assert_msg(fadt, "Unable to find ACPI FADT");
+	assert_msg(fadt->arm_boot_flags & ACPI_FADT_PSCI_COMPLIANT,
+		   "PSCI is not supported in this platform");
+
+	if (fadt->arm_boot_flags & ACPI_FADT_PSCI_USE_HVC)
+		psci_invoke = psci_invoke_hvc;
+	else
+		psci_invoke = psci_invoke_smc;
+}
+
+#else
+
+static void psci_set_conduit_acpi(void)
+{
+	assert_msg(false, "ACPI not available");
+}
+
+#endif
+
+void psci_set_conduit(void)
+{
+	if (dt_available())
+		psci_set_conduit_fdt();
+	else
+		psci_set_conduit_acpi();
+}
-- 
2.25.1