[RFC PATCH 13/36] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

[James Morse <james.morse@arm.com>]

Probing MPAM is convoluted. MSCs that are integrated with a CPU may
only be accessible from those CPUs, and they may not be online.
Touching the hardware early is pointless as MPAM can't be used until
the system-wide common values for num_partid and num_pmg have been
discovered.

Start with driver probe/remove and mapping the MSC.

CC: Carl Worth <carl@os.amperecomputing.com>
Signed-off-by: James Morse <james.morse@arm.com>
---
 arch/arm64/Kconfig                          |   1 +
 drivers/platform/arm64/Kconfig              |   1 +
 drivers/platform/arm64/Makefile             |   1 +
 drivers/platform/arm64/mpam/Kconfig         |  10 +
 drivers/platform/arm64/mpam/Makefile        |   4 +
 drivers/platform/arm64/mpam/mpam_devices.c  | 336 ++++++++++++++++++++
 drivers/platform/arm64/mpam/mpam_internal.h |  62 ++++
 7 files changed, 415 insertions(+)
 create mode 100644 drivers/platform/arm64/mpam/Kconfig
 create mode 100644 drivers/platform/arm64/mpam/Makefile
 create mode 100644 drivers/platform/arm64/mpam/mpam_devices.c
 create mode 100644 drivers/platform/arm64/mpam/mpam_internal.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ad9a49a39e41..8abce7f4eb1e 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2060,6 +2060,7 @@ config ARM64_TLB_RANGE
 
 config ARM64_MPAM
 	bool "Enable support for MPAM"
+	select ARM64_MPAM_DRIVER
 	select ACPI_MPAM if ACPI
 	help
 	  Memory Partitioning and Monitoring is an optional extension
diff --git a/drivers/platform/arm64/Kconfig b/drivers/platform/arm64/Kconfig
index 1eb8ab0855e5..16a927cf6ea2 100644
--- a/drivers/platform/arm64/Kconfig
+++ b/drivers/platform/arm64/Kconfig
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 source "drivers/platform/arm64/ec/Kconfig"
+source "drivers/platform/arm64/mpam/Kconfig"
diff --git a/drivers/platform/arm64/Makefile b/drivers/platform/arm64/Makefile
index ce840a8cf8cc..c6ec3bc6a100 100644
--- a/drivers/platform/arm64/Makefile
+++ b/drivers/platform/arm64/Makefile
@@ -1,3 +1,4 @@
 # SPDX-License-Identifier: GPL-2.0-only
 
 obj-y             += ec/
+obj-y             += mpam/
diff --git a/drivers/platform/arm64/mpam/Kconfig b/drivers/platform/arm64/mpam/Kconfig
new file mode 100644
index 000000000000..b63495d7da87
--- /dev/null
+++ b/drivers/platform/arm64/mpam/Kconfig
@@ -0,0 +1,10 @@
+# Confusingly, this is everything but the CPU bits of MPAM. CPU here means
+# CPU resources, not containers or cgroups etc.
+config ARM_CPU_RESCTRL
+	bool
+	depends on ARM64
+
+config ARM64_MPAM_DRIVER_DEBUG
+	bool "Enable debug messages from the MPAM driver."
+	help
+	  Say yes here to enable debug messages from the MPAM driver.
diff --git a/drivers/platform/arm64/mpam/Makefile b/drivers/platform/arm64/mpam/Makefile
new file mode 100644
index 000000000000..4255975c7724
--- /dev/null
+++ b/drivers/platform/arm64/mpam/Makefile
@@ -0,0 +1,4 @@
+obj-$(CONFIG_ARM64_MPAM)			+= mpam.o
+mpam-y						+= mpam_devices.o
+
+cflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)	+= -DDEBUG
diff --git a/drivers/platform/arm64/mpam/mpam_devices.c b/drivers/platform/arm64/mpam/mpam_devices.c
new file mode 100644
index 000000000000..5b886ba54ba8
--- /dev/null
+++ b/drivers/platform/arm64/mpam/mpam_devices.c
@@ -0,0 +1,336 @@
+// SPDX-License-Identifier: GPL-2.0
+// Copyright (C) 2025 Arm Ltd.
+
+#define pr_fmt(fmt) "%s:%s: " fmt, KBUILD_MODNAME, __func__
+
+#include <linux/acpi.h>
+#include <linux/arm_mpam.h>
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/cpumask.h>
+#include <linux/device.h>
+#include <linux/errno.h>
+#include <linux/gfp.h>
+#include <linux/list.h>
+#include <linux/lockdep.h>
+#include <linux/mutex.h>
+#include <linux/of.h>
+#include <linux/of_platform.h>
+#include <linux/platform_device.h>
+#include <linux/printk.h>
+#include <linux/slab.h>
+#include <linux/spinlock.h>
+#include <linux/srcu.h>
+#include <linux/types.h>
+
+#include <acpi/pcc.h>
+
+#include "mpam_internal.h"
+
+/*
+ * mpam_list_lock protects the SRCU lists when writing. Once the
+ * mpam_enabled key is enabled these lists are read-only,
+ * unless the error interrupt disables the driver.
+ */
+static DEFINE_MUTEX(mpam_list_lock);
+static LIST_HEAD(mpam_all_msc);
+
+static struct srcu_struct mpam_srcu;
+
+/* MPAM isn't available until all the MSC have been probed. */
+static u32 mpam_num_msc;
+
+static void mpam_discovery_complete(void)
+{
+	pr_err("Discovered all MSC\n");
+}
+
+static int mpam_dt_count_msc(void)
+{
+	int count = 0;
+	struct device_node *np;
+
+	for_each_compatible_node(np, NULL, "arm,mpam-msc")
+		count++;
+
+	return count;
+}
+
+static int mpam_dt_parse_resource(struct mpam_msc *msc, struct device_node *np,
+				  u32 ris_idx)
+{
+	int err = 0;
+	u32 level = 0;
+	unsigned long cache_id;
+	struct device_node *cache;
+
+	do {
+		if (of_device_is_compatible(np, "arm,mpam-cache")) {
+			cache = of_parse_phandle(np, "arm,mpam-device", 0);
+			if (!cache) {
+				pr_err("Failed to read phandle\n");
+				break;
+			}
+		} else if (of_device_is_compatible(np->parent, "cache")) {
+			cache = of_node_get(np->parent);
+		} else {
+			/* For now, only caches are supported */
+			cache = NULL;
+			break;
+		}
+
+		err = of_property_read_u32(cache, "cache-level", &level);
+		if (err) {
+			pr_err("Failed to read cache-level\n");
+			break;
+		}
+
+		cache_id = cache_of_calculate_id(cache);
+		if (cache_id == ~0UL) {
+			err = -ENOENT;
+			break;
+		}
+
+		err = mpam_ris_create(msc, ris_idx, MPAM_CLASS_CACHE, level,
+				      cache_id);
+	} while (0);
+	of_node_put(cache);
+
+	return err;
+}
+
+static int mpam_dt_parse_resources(struct mpam_msc *msc, void *ignored)
+{
+	int err, num_ris = 0;
+	const u32 *ris_idx_p;
+	struct device_node *iter, *np;
+
+	np = msc->pdev->dev.of_node;
+	for_each_child_of_node(np, iter) {
+		ris_idx_p = of_get_property(iter, "reg", NULL);
+		if (ris_idx_p) {
+			num_ris++;
+			err = mpam_dt_parse_resource(msc, iter, *ris_idx_p);
+			if (err) {
+				of_node_put(iter);
+				return err;
+			}
+		}
+	}
+
+	if (!num_ris)
+		mpam_dt_parse_resource(msc, np, 0);
+
+	return err;
+}
+
+/*
+ * An MSC can control traffic from a set of CPUs, but may only be accessible
+ * from a (hopefully wider) set of CPUs. The common reason for this is power
+ * management. If all the CPUs in a cluster are in PSCI:CPU_SUSPEND, the
+ * the corresponding cache may also be powered off. By making accesses from
+ * one of those CPUs, we ensure this isn't the case.
+ */
+static int update_msc_accessibility(struct mpam_msc *msc)
+{
+	struct device_node *parent;
+	u32 affinity_id;
+	int err;
+
+	if (!acpi_disabled) {
+		err = device_property_read_u32(&msc->pdev->dev, "cpu_affinity",
+					       &affinity_id);
+		if (err) {
+			cpumask_copy(&msc->accessibility, cpu_possible_mask);
+			err = 0;
+		} else {
+			err = acpi_pptt_get_cpus_from_container(affinity_id,
+								&msc->accessibility);
+		}
+
+		return err;
+	}
+
+	/* This depends on the path to of_node */
+	parent = of_get_parent(msc->pdev->dev.of_node);
+	if (parent == of_root) {
+		cpumask_copy(&msc->accessibility, cpu_possible_mask);
+		err = 0;
+	} else {
+		err = -EINVAL;
+		pr_err("Cannot determine accessibility of MSC: %s\n",
+		       dev_name(&msc->pdev->dev));
+	}
+	of_node_put(parent);
+
+	return err;
+}
+
+static int fw_num_msc;
+
+static void mpam_pcc_rx_callback(struct mbox_client *cl, void *msg)
+{
+	/* TODO: wake up tasks blocked on this MSC's PCC channel */
+}
+
+static void mpam_msc_drv_remove(struct platform_device *pdev)
+{
+	struct mpam_msc *msc = platform_get_drvdata(pdev);
+
+	if (!msc)
+		return;
+
+	mutex_lock(&mpam_list_lock);
+	mpam_num_msc--;
+	platform_set_drvdata(pdev, NULL);
+	list_del_rcu(&msc->glbl_list);
+	synchronize_srcu(&mpam_srcu);
+	devm_kfree(&pdev->dev, msc);
+	mutex_unlock(&mpam_list_lock);
+}
+
+static int mpam_msc_drv_probe(struct platform_device *pdev)
+{
+	int err;
+	struct mpam_msc *msc;
+	struct resource *msc_res;
+	void *plat_data = pdev->dev.platform_data;
+
+	mutex_lock(&mpam_list_lock);
+	do {
+		msc = devm_kzalloc(&pdev->dev, sizeof(*msc), GFP_KERNEL);
+		if (!msc) {
+			err = -ENOMEM;
+			break;
+		}
+
+		mutex_init(&msc->probe_lock);
+		mutex_init(&msc->part_sel_lock);
+		mutex_init(&msc->outer_mon_sel_lock);
+		raw_spin_lock_init(&msc->inner_mon_sel_lock);
+		msc->id = mpam_num_msc++;
+		msc->pdev = pdev;
+		INIT_LIST_HEAD_RCU(&msc->glbl_list);
+		INIT_LIST_HEAD_RCU(&msc->ris);
+
+		err = update_msc_accessibility(msc);
+		if (err)
+			break;
+		if (cpumask_empty(&msc->accessibility)) {
+			pr_err_once("msc:%u is not accessible from any CPU!",
+				    msc->id);
+			err = -EINVAL;
+			break;
+		}
+
+		if (device_property_read_u32(&pdev->dev, "pcc-channel",
+					     &msc->pcc_subspace_id))
+			msc->iface = MPAM_IFACE_MMIO;
+		else
+			msc->iface = MPAM_IFACE_PCC;
+
+		if (msc->iface == MPAM_IFACE_MMIO) {
+			void __iomem *io;
+
+			io = devm_platform_get_and_ioremap_resource(pdev, 0,
+								    &msc_res);
+			if (IS_ERR(io)) {
+				pr_err("Failed to map MSC base address\n");
+				err = PTR_ERR(io);
+				break;
+			}
+			msc->mapped_hwpage_sz = msc_res->end - msc_res->start;
+			msc->mapped_hwpage = io;
+		} else if (msc->iface == MPAM_IFACE_PCC) {
+			msc->pcc_cl.dev = &pdev->dev;
+			msc->pcc_cl.rx_callback = mpam_pcc_rx_callback;
+			msc->pcc_cl.tx_block = false;
+			msc->pcc_cl.tx_tout = 1000; /* 1s */
+			msc->pcc_cl.knows_txdone = false;
+
+			msc->pcc_chan = pcc_mbox_request_channel(&msc->pcc_cl,
+								 msc->pcc_subspace_id);
+			if (IS_ERR(msc->pcc_chan)) {
+				pr_err("Failed to request MSC PCC channel\n");
+				err = PTR_ERR(msc->pcc_chan);
+				break;
+			}
+		}
+
+		list_add_rcu(&msc->glbl_list, &mpam_all_msc);
+		platform_set_drvdata(pdev, msc);
+	} while (0);
+	mutex_unlock(&mpam_list_lock);
+
+	if (!err) {
+		/* Create RIS entries described by firmware */
+		if (!acpi_disabled)
+			err = acpi_mpam_parse_resources(msc, plat_data);
+		else
+			err = mpam_dt_parse_resources(msc, plat_data);
+	}
+
+	if (!err && fw_num_msc == mpam_num_msc)
+		mpam_discovery_complete();
+
+	if (err && msc)
+		mpam_msc_drv_remove(pdev);
+
+	return err;
+}
+
+static const struct of_device_id mpam_of_match[] = {
+	{ .compatible = "arm,mpam-msc", },
+	{},
+};
+MODULE_DEVICE_TABLE(of, mpam_of_match);
+
+static struct platform_driver mpam_msc_driver = {
+	.driver = {
+		.name = "mpam_msc",
+		.of_match_table = of_match_ptr(mpam_of_match),
+	},
+	.probe = mpam_msc_drv_probe,
+	.remove = mpam_msc_drv_remove,
+};
+
+/*
+ * MSC that are hidden under caches are not created as platform devices
+ * as there is no cache driver. Caches are also special-cased in
+ * update_msc_accessibility().
+ */
+static void mpam_dt_create_foundling_msc(void)
+{
+	int err;
+	struct device_node *cache;
+
+	for_each_compatible_node(cache, NULL, "cache") {
+		err = of_platform_populate(cache, mpam_of_match, NULL, NULL);
+		if (err)
+			pr_err("Failed to create MSC devices under caches\n");
+	}
+}
+
+static int __init mpam_msc_driver_init(void)
+{
+	if (!system_supports_mpam())
+		return -EOPNOTSUPP;
+
+	init_srcu_struct(&mpam_srcu);
+
+	if (!acpi_disabled)
+		fw_num_msc = acpi_mpam_count_msc();
+	else
+		fw_num_msc = mpam_dt_count_msc();
+
+	if (fw_num_msc <= 0) {
+		pr_err("No MSC devices found in firmware\n");
+		return -EINVAL;
+	}
+
+	if (acpi_disabled)
+		mpam_dt_create_foundling_msc();
+
+	return platform_driver_register(&mpam_msc_driver);
+}
+subsys_initcall(mpam_msc_driver_init);
diff --git a/drivers/platform/arm64/mpam/mpam_internal.h b/drivers/platform/arm64/mpam/mpam_internal.h
new file mode 100644
index 000000000000..07e0f240eaca
--- /dev/null
+++ b/drivers/platform/arm64/mpam/mpam_internal.h
@@ -0,0 +1,62 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2024 Arm Ltd.
+
+#ifndef MPAM_INTERNAL_H
+#define MPAM_INTERNAL_H
+
+#include <linux/arm_mpam.h>
+#include <linux/cpumask.h>
+#include <linux/io.h>
+#include <linux/mailbox_client.h>
+#include <linux/mutex.h>
+#include <linux/resctrl.h>
+#include <linux/sizes.h>
+
+struct mpam_msc {
+	/* member of mpam_all_msc */
+	struct list_head        glbl_list;
+
+	int			id;
+	struct platform_device *pdev;
+
+	/* Not modified after mpam_is_enabled() becomes true */
+	enum mpam_msc_iface	iface;
+	u32			pcc_subspace_id;
+	struct mbox_client	pcc_cl;
+	struct pcc_mbox_chan	*pcc_chan;
+	u32			nrdy_usec;
+	cpumask_t		accessibility;
+
+	/*
+	 * probe_lock is only take during discovery. After discovery these
+	 * properties become read-only and the lists are protected by SRCU.
+	 */
+	struct mutex		probe_lock;
+	unsigned long		ris_idxs[128 / BITS_PER_LONG];
+	u32			ris_max;
+
+	/* mpam_msc_ris of this component */
+	struct list_head	ris;
+
+	/*
+	 * part_sel_lock protects access to the MSC hardware registers that are
+	 * affected by MPAMCFG_PART_SEL. (including the ID registers that vary
+	 * by RIS).
+	 * If needed, take msc->lock first.
+	 */
+	struct mutex		part_sel_lock;
+
+	/*
+	 * mon_sel_lock protects access to the MSC hardware registers that are
+	 * affeted by MPAMCFG_MON_SEL.
+	 * If needed, take msc->lock first.
+	 */
+	struct mutex		outer_mon_sel_lock;
+	raw_spinlock_t		inner_mon_sel_lock;
+	unsigned long		inner_mon_sel_flags;
+
+	void __iomem		*mapped_hwpage;
+	size_t			mapped_hwpage_sz;
+};
+
+#endif /* MPAM_INTERNAL_H */
-- 
2.39.5