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Date: Wed, 18 May 2022 15:30:25 +0900
From: Kohei Tarumizu <tarumizu.kohei@...itsu.com>
To: catalin.marinas@....com, will@...nel.org, tglx@...utronix.de,
mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
x86@...nel.org, hpa@...or.com, gregkh@...uxfoundation.org,
rafael@...nel.org, mchehab+huawei@...nel.org, eugenis@...gle.com,
tony.luck@...el.com, pcc@...gle.com, peterz@...radead.org,
marcos@...a.pet, conor.dooley@...rochip.com,
nicolas.ferre@...rochip.com, marcan@...can.st,
linus.walleij@...aro.org, arnd@...db.de,
linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Cc: tarumizu.kohei@...itsu.com
Subject: [PATCH v4 1/8] drivers: base: Add hardware prefetch control core driver
Adds a register/unregister function to provide sysfs interface to
control CPU's hardware prefetch behavior. It creates the
"prefetch_control" sysfs directory and some attributes.
Attributes are hardware dependent, so it must be implemented for each
hardware. If CPU has a hardware prefetch behavior, call this function
to create sysfs.
Following patches add support for A64FX and x86.
Signed-off-by: Kohei Tarumizu <tarumizu.kohei@...itsu.com>
---
drivers/base/pfctl.c | 180 ++++++++++++++++++++++++++++++++++++++++++
include/linux/pfctl.h | 14 ++++
2 files changed, 194 insertions(+)
create mode 100644 drivers/base/pfctl.c
create mode 100644 include/linux/pfctl.h
diff --git a/drivers/base/pfctl.c b/drivers/base/pfctl.c
new file mode 100644
index 000000000000..08ee8faaf277
--- /dev/null
+++ b/drivers/base/pfctl.c
@@ -0,0 +1,180 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Hardware prefetch control support via sysfs.
+ *
+ * Copyright 2022 FUJITSU LIMITED
+ *
+ * See Documentation/ABI/testing/sysfs-devices-system-cpu for more information.
+ */
+
+#include <linux/cacheinfo.h>
+#include <linux/cpu.h>
+#include <linux/device.h>
+#include <linux/pfctl.h>
+#include <linux/slab.h>
+
+#ifdef pr_fmt
+#undef pr_fmt
+#endif
+#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
+
+const struct pfctl_group *pgroups;
+enum cpuhp_state hp_online;
+
+static struct device_attribute **
+get_pfctl_attribute(unsigned int level, enum cache_type type)
+{
+ int i;
+
+ for (i = 0; pgroups[i].attrs; i++)
+ if ((level == pgroups[i].level) && (type == pgroups[i].type))
+ return pgroups[i].attrs;
+
+ return NULL;
+}
+
+static int remove_pfctl_attr(struct device *index_dev, void *data)
+{
+ struct cacheinfo *leaf = dev_get_drvdata(index_dev);
+ struct device_attribute **attrs;
+ struct device *pfctl_dev;
+ int i;
+
+ attrs = get_pfctl_attribute(leaf->level, leaf->type);
+ if (!attrs)
+ return 0;
+
+ pfctl_dev = device_find_child_by_name(index_dev, "prefetch_control");
+ if (!pfctl_dev)
+ return 0;
+
+ for (i = 0; attrs[i]; i++)
+ device_remove_file(pfctl_dev, attrs[i]);
+
+ device_unregister(pfctl_dev);
+ put_device(pfctl_dev);
+
+ pfctl_dev = NULL;
+
+ return 0;
+}
+
+static int create_pfctl_attr(struct device *index_dev, void *data)
+{
+ struct cacheinfo *leaf = dev_get_drvdata(index_dev);
+ struct device_attribute **attrs;
+ struct device *pfctl_dev;
+ int i, err;
+
+ attrs = get_pfctl_attribute(leaf->level, leaf->type);
+ if (!attrs)
+ return 0;
+
+ pfctl_dev = cpu_device_create(index_dev, NULL, NULL,
+ "prefetch_control");
+ if (IS_ERR(pfctl_dev))
+ return PTR_ERR(pfctl_dev);
+
+ for (i = 0; attrs[i]; i++) {
+ err = device_create_file(pfctl_dev, attrs[i]);
+ if (err) {
+ while (--i >= 0)
+ device_remove_file(pfctl_dev, attrs[i]);
+
+ device_unregister(pfctl_dev);
+ pfctl_dev = NULL;
+
+ return err;
+ }
+ }
+
+ return 0;
+}
+
+static int pfctl_online(unsigned int cpu)
+{
+ struct device *cpu_dev = get_cpu_device(cpu);
+ struct device *cache_dev;
+ int ret;
+
+ cache_dev = device_find_child_by_name(cpu_dev, "cache");
+ if (!cache_dev)
+ return -ENODEV;
+
+ ret = device_for_each_child(cache_dev, NULL, create_pfctl_attr);
+ if (ret < 0)
+ device_for_each_child(cache_dev, NULL, remove_pfctl_attr);
+
+ put_device(cache_dev);
+
+ return ret;
+}
+
+static int pfctl_prepare_down(unsigned int cpu)
+{
+ struct device *cpu_dev = get_cpu_device(cpu);
+ struct device *cache_dev;
+
+ cache_dev = device_find_child_by_name(cpu_dev, "cache");
+ if (!cache_dev)
+ return 0;
+
+ device_for_each_child(cache_dev, NULL, remove_pfctl_attr);
+
+ put_device(cache_dev);
+
+ return 0;
+}
+
+/**
+ * pfctl_register_attrs - register a Hardware Prefetch Control attributes
+ * @pfctl_groups: pfctl_groups contains device attribute group to control the
+ * hardware prefetch register.
+ *
+ * Note: Call this function after the cache device is initialized because it
+ * requires access to the cache device. (e.g. Call at the late_initcall)
+ *
+ * Context: Any context.
+ * Return: 0 on success, negative error code on failure.
+ */
+int pfctl_register_attrs(const struct pfctl_group *pfctl_groups)
+{
+ int ret;
+
+ if (pgroups)
+ return -EEXIST;
+
+ pgroups = pfctl_groups;
+
+ ret = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "base/pfctl:online",
+ pfctl_online, pfctl_prepare_down);
+ if (ret < 0) {
+ pr_err("failed to register hotplug callbacks\n");
+ pgroups = NULL;
+ return ret;
+ }
+
+ hp_online = ret;
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pfctl_register_attrs);
+
+/**
+ * pfctl_unregister_attrs - unregister the Hardware Prefetch Control driver
+ * @pfctl_groups: Used to verify that this function is called by the same driver
+ * that called pfctl_register_attrs.
+ *
+ * Context: Any context.
+ * Return: nothing.
+ */
+void pfctl_unregister_attrs(const struct pfctl_group *pfctl_groups)
+{
+ if (!pgroups || (pfctl_groups != pgroups))
+ return;
+
+ cpuhp_remove_state(hp_online);
+
+ pgroups = NULL;
+}
+EXPORT_SYMBOL_GPL(pfctl_unregister_attrs);
diff --git a/include/linux/pfctl.h b/include/linux/pfctl.h
new file mode 100644
index 000000000000..ecdab78be09f
--- /dev/null
+++ b/include/linux/pfctl.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LINUX_PFCTL_H
+#define _LINUX_PFCTL_H
+
+struct pfctl_group {
+ unsigned int level;
+ enum cache_type type;
+ struct device_attribute **attrs;
+};
+
+int pfctl_register_attrs(const struct pfctl_group *pfctl_groups);
+void pfctl_unregister_attrs(const struct pfctl_group *pfctl_groups);
+
+#endif
--
2.27.0
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