feat(mpmm): add support for MPMM

MPMM - the Maximum Power Mitigation Mechanism - is an optional
microarchitectural feature present on some Armv9-A cores, introduced
with the Cortex-X2, Cortex-A710 and Cortex-A510 cores.

MPMM allows the SoC firmware to detect and limit high activity events
to assist in SoC processor power domain dynamic power budgeting and
limit the triggering of whole-rail (i.e. clock chopping) responses to
overcurrent conditions.

This feature is enabled via the `ENABLE_MPMM` build option.
Configuration can be done via FCONF by enabling `ENABLE_MPMM_FCONF`, or
by via the plaform-implemented `plat_mpmm_topology` function.

Change-Id: I77da82808ad4744ece8263f0bf215c5a091c3167
Signed-off-by: Chris Kay <chris.kay@arm.com>

2 files changed, 83 insertions, 0 deletions

diff --git a/lib/fconf/fconf.mk b/lib/fconf/fconf.mk
index 18bcb3590..fb8891031 100644
--- a/lib/fconf/fconf.mk
+++ b/lib/fconf/fconf.mk
@@ -14,3 +14,6 @@ FCONF_DYN_SOURCES	+=	${FDT_WRAPPERS_SOURCES}
 
 FCONF_AMU_SOURCES	:=	lib/fconf/fconf_amu_getter.c
 FCONF_AMU_SOURCES	+=	${FDT_WRAPPERS_SOURCES}
+
+FCONF_MPMM_SOURCES	:=	lib/fconf/fconf_mpmm_getter.c
+FCONF_MPMM_SOURCES	+=	${FDT_WRAPPERS_SOURCES}
diff --git a/lib/fconf/fconf_mpmm_getter.c b/lib/fconf/fconf_mpmm_getter.c
new file mode 100644
index 000000000..02a566d5a
--- /dev/null
+++ b/lib/fconf/fconf_mpmm_getter.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright (c) 2021, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include <common/debug.h>
+#include <common/fdt_wrappers.h>
+#include <lib/fconf/fconf.h>
+#include <lib/fconf/fconf_mpmm_getter.h>
+#include <libfdt.h>
+
+#include <plat/common/platform.h>
+
+struct fconf_mpmm_config fconf_mpmm_config;
+static struct mpmm_topology fconf_mpmm_topology;
+
+/*
+ * Within a `cpu` node, determine support for MPMM via the `supports-mpmm`
+ * property.
+ *
+ * Returns `0` on success, or a negative integer representing an error code.
+ */
+static int fconf_populate_mpmm_cpu(const void *fdt, int off, uintptr_t mpidr)
+{
+	int ret, len;
+
+	int core_pos;
+	struct mpmm_core *core;
+
+	core_pos = plat_core_pos_by_mpidr(mpidr);
+	if (core_pos < 0) {
+		return -FDT_ERR_BADVALUE;
+	}
+
+	core = &fconf_mpmm_topology.cores[core_pos];
+
+	fdt_getprop(fdt, off, "supports-mpmm", &len);
+	if (len >= 0) {
+		core->supported = true;
+		ret = 0;
+	} else {
+		core->supported = false;
+		ret = len;
+	}
+
+	return ret;
+}
+
+/*
+ * Populates the global `fconf_mpmm_config` structure based on what's described
+ * by the hardware configuration device tree blob.
+ *
+ * The device tree is expected to provide a `supports-mpmm` property for each
+ * `cpu` node, like so:
+ *
+ *     cpu@0 {
+ *       supports-mpmm;
+ *     };
+ *
+ * This property indicates whether the core implements MPMM, as we cannot detect
+ * support for it dynamically.
+ */
+static int fconf_populate_mpmm(uintptr_t config)
+{
+	int ret = fdtw_for_each_cpu(
+		(const void *)config, fconf_populate_mpmm_cpu);
+	if (ret == 0) {
+		fconf_mpmm_config.topology = &fconf_mpmm_topology;
+	} else {
+		ERROR("FCONF: failed to configure MPMM: %d\n", ret);
+	}
+
+	return ret;
+}
+
+FCONF_REGISTER_POPULATOR(HW_CONFIG, mpmm, fconf_populate_mpmm);