Message-ID: <20251107123450.664001-11-ben.horgan@arm.com>
Date: Fri,  7 Nov 2025 12:34:27 +0000
From: Ben Horgan <ben.horgan@....com>
To: james.morse@....com
Cc: amitsinght@...vell.com,
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	Shaopeng Tan <tan.shaopeng@...fujitsu.com>,
	Ben Horgan <ben.horgan@....com>
Subject: [PATCH 10/33] arm_mpam: Add probe/remove for mpam msc driver and kbuild boiler plate

From: James Morse <james.morse@....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@...amperecomputing.com>
Tested-by: Fenghua Yu <fenghuay@...dia.com>
Tested-by: Shaopeng Tan <tan.shaopeng@...fujitsu.com>
Tested-by: Peter Newman <peternewman@...gle.com>
Signed-off-by: James Morse <james.morse@....com>
Signed-off-by: Ben Horgan <ben.horgan@....com>
---
Changes since v3:
>From Jonathan:
Include cleanup
Use devm_mutex_init()
Add an ERR_CAST()
Fenghua:
Return zero from update_msc_accessibility()
Additional:
Fail probe if MSC doesn't have an MMIO interface
---
 arch/arm64/Kconfig              |   1 +
 drivers/Kconfig                 |   2 +
 drivers/Makefile                |   1 +
 drivers/resctrl/Kconfig         |  15 +++
 drivers/resctrl/Makefile        |   4 +
 drivers/resctrl/mpam_devices.c  | 194 ++++++++++++++++++++++++++++++++
 drivers/resctrl/mpam_internal.h |  49 ++++++++
 7 files changed, 266 insertions(+)
 create mode 100644 drivers/resctrl/Kconfig
 create mode 100644 drivers/resctrl/Makefile
 create mode 100644 drivers/resctrl/mpam_devices.c
 create mode 100644 drivers/resctrl/mpam_internal.h

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index c5e66d5d72cd..004d58cfbff8 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -2025,6 +2025,7 @@ config ARM64_TLB_RANGE
 
 config ARM64_MPAM
 	bool "Enable support for MPAM"
+	select ARM64_MPAM_DRIVER if EXPERT	# does nothing yet
 	select ACPI_MPAM if ACPI
 	help
 	  Memory System Resource Partitioning and Monitoring (MPAM) is an
diff --git a/drivers/Kconfig b/drivers/Kconfig
index 4915a63866b0..3054b50a2f4c 100644
--- a/drivers/Kconfig
+++ b/drivers/Kconfig
@@ -251,4 +251,6 @@ source "drivers/hte/Kconfig"
 
 source "drivers/cdx/Kconfig"
 
+source "drivers/resctrl/Kconfig"
+
 endmenu
diff --git a/drivers/Makefile b/drivers/Makefile
index 8e1ffa4358d5..20eb17596b89 100644
--- a/drivers/Makefile
+++ b/drivers/Makefile
@@ -194,6 +194,7 @@ obj-$(CONFIG_HTE)		+= hte/
 obj-$(CONFIG_DRM_ACCEL)		+= accel/
 obj-$(CONFIG_CDX_BUS)		+= cdx/
 obj-$(CONFIG_DPLL)		+= dpll/
+obj-y				+= resctrl/
 
 obj-$(CONFIG_DIBS)		+= dibs/
 obj-$(CONFIG_S390)		+= s390/
diff --git a/drivers/resctrl/Kconfig b/drivers/resctrl/Kconfig
new file mode 100644
index 000000000000..ef2f3adf64a9
--- /dev/null
+++ b/drivers/resctrl/Kconfig
@@ -0,0 +1,15 @@
+menuconfig ARM64_MPAM_DRIVER
+	bool "MPAM driver"
+	depends on ARM64 && ARM64_MPAM && EXPERT
+	help
+	  Memory System Resource Partitioning and Monitoring (MPAM) driver for
+	  System IP, e,g. caches and memory controllers.
+
+if ARM64_MPAM_DRIVER
+
+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.
+
+endif
diff --git a/drivers/resctrl/Makefile b/drivers/resctrl/Makefile
new file mode 100644
index 000000000000..898199dcf80d
--- /dev/null
+++ b/drivers/resctrl/Makefile
@@ -0,0 +1,4 @@
+obj-$(CONFIG_ARM64_MPAM_DRIVER)			+= mpam.o
+mpam-y						+= mpam_devices.o
+
+ccflags-$(CONFIG_ARM64_MPAM_DRIVER_DEBUG)	+= -DDEBUG
diff --git a/drivers/resctrl/mpam_devices.c b/drivers/resctrl/mpam_devices.c
new file mode 100644
index 000000000000..6c6be133d73a
--- /dev/null
+++ b/drivers/resctrl/mpam_devices.c
@@ -0,0 +1,194 @@
+// 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/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/platform_device.h>
+#include <linux/printk.h>
+#include <linux/srcu.h>
+#include <linux/types.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);
+
+struct srcu_struct mpam_srcu;
+
+/*
+ * Number of MSCs that have been probed. Once all MSC have been probed MPAM
+ * can be enabled.
+ */
+static atomic_t mpam_num_msc;
+
+/*
+ * 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
+ * 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)
+{
+	u32 affinity_id;
+	int err;
+
+	err = device_property_read_u32(&msc->pdev->dev, "cpu_affinity",
+				       &affinity_id);
+	if (err)
+		cpumask_copy(&msc->accessibility, cpu_possible_mask);
+	else
+		acpi_pptt_get_cpus_from_container(affinity_id,
+						  &msc->accessibility);
+	return 0;
+}
+
+static int fw_num_msc;
+
+static void mpam_msc_destroy(struct mpam_msc *msc)
+{
+	struct platform_device *pdev = msc->pdev;
+
+	lockdep_assert_held(&mpam_list_lock);
+
+	list_del_rcu(&msc->all_msc_list);
+	platform_set_drvdata(pdev, NULL);
+}
+
+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_msc_destroy(msc);
+	mutex_unlock(&mpam_list_lock);
+
+	synchronize_srcu(&mpam_srcu);
+}
+
+static struct mpam_msc *do_mpam_msc_drv_probe(struct platform_device *pdev)
+{
+	int err;
+	u32 tmp;
+	struct mpam_msc *msc;
+	struct resource *msc_res;
+	struct device *dev = &pdev->dev;
+
+	lockdep_assert_held(&mpam_list_lock);
+
+	msc = devm_kzalloc(&pdev->dev, sizeof(*msc), GFP_KERNEL);
+	if (!msc)
+		return ERR_PTR(-ENOMEM);
+
+	err = devm_mutex_init(dev, &msc->probe_lock);
+	if (err)
+		return ERR_PTR(err);
+	err = devm_mutex_init(dev, &msc->part_sel_lock);
+	if (err)
+		return ERR_PTR(err);
+	msc->id = pdev->id;
+	msc->pdev = pdev;
+	INIT_LIST_HEAD_RCU(&msc->all_msc_list);
+	INIT_LIST_HEAD_RCU(&msc->ris);
+
+	err = update_msc_accessibility(msc);
+	if (err)
+		return ERR_PTR(err);
+	if (cpumask_empty(&msc->accessibility)) {
+		dev_err_once(dev, "MSC is not accessible from any CPU!");
+		return ERR_PTR(-EINVAL);
+	}
+
+	if (device_property_read_u32(&pdev->dev, "pcc-channel", &tmp))
+		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)) {
+			dev_err_once(dev, "Failed to map MSC base address\n");
+			return ERR_CAST(io);
+		}
+		msc->mapped_hwpage_sz = msc_res->end - msc_res->start;
+		msc->mapped_hwpage = io;
+	} else {
+		return ERR_PTR(-ENOENT);
+	}
+
+	list_add_rcu(&msc->all_msc_list, &mpam_all_msc);
+	platform_set_drvdata(pdev, msc);
+
+	return msc;
+}
+
+static int mpam_msc_drv_probe(struct platform_device *pdev)
+{
+	int err;
+	struct mpam_msc *msc = NULL;
+	void *plat_data = pdev->dev.platform_data;
+
+	mutex_lock(&mpam_list_lock);
+	msc = do_mpam_msc_drv_probe(pdev);
+	mutex_unlock(&mpam_list_lock);
+	if (!IS_ERR(msc)) {
+		/* Create RIS entries described by firmware */
+		err = acpi_mpam_parse_resources(msc, plat_data);
+		if (err)
+			mpam_msc_drv_remove(pdev);
+	} else {
+		err = PTR_ERR(msc);
+	}
+
+	if (!err && atomic_add_return(1, &mpam_num_msc) == fw_num_msc)
+		pr_info("Discovered all MSC\n");
+
+	return err;
+}
+
+static struct platform_driver mpam_msc_driver = {
+	.driver = {
+		.name = "mpam_msc",
+	},
+	.probe = mpam_msc_drv_probe,
+	.remove = mpam_msc_drv_remove,
+};
+
+static int __init mpam_msc_driver_init(void)
+{
+	if (!system_supports_mpam())
+		return -EOPNOTSUPP;
+
+	init_srcu_struct(&mpam_srcu);
+
+	fw_num_msc = acpi_mpam_count_msc();
+
+	if (fw_num_msc <= 0) {
+		pr_err("No MSC devices found in firmware\n");
+		return -EINVAL;
+	}
+
+	return platform_driver_register(&mpam_msc_driver);
+}
+subsys_initcall(mpam_msc_driver_init);
diff --git a/drivers/resctrl/mpam_internal.h b/drivers/resctrl/mpam_internal.h
new file mode 100644
index 000000000000..540066903eca
--- /dev/null
+++ b/drivers/resctrl/mpam_internal.h
@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+// Copyright (C) 2025 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/mutex.h>
+#include <linux/types.h>
+
+struct platform_device;
+
+struct mpam_msc {
+	/* member of mpam_all_msc */
+	struct list_head	all_msc_list;
+
+	int			id;
+	struct platform_device	*pdev;
+
+	/* Not modified after mpam_is_enabled() becomes true */
+	enum mpam_msc_iface	iface;
+	u32			nrdy_usec;
+	cpumask_t		accessibility;
+
+	/*
+	 * probe_lock is only taken during discovery. After discovery these
+	 * properties become read-only and the lists are protected by SRCU.
+	 */
+	struct mutex		probe_lock;
+	unsigned long		ris_idxs;
+	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->probe_lock first.
+	 */
+	struct mutex		part_sel_lock;
+
+	void __iomem		*mapped_hwpage;
+	size_t			mapped_hwpage_sz;
+};
+#endif /* MPAM_INTERNAL_H */
-- 
2.43.0

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