DCA: Add Direct Cache Access driver
authorShannon Nelson <shannon.nelson@intel.com>
Tue, 16 Oct 2007 08:27:41 +0000 (01:27 -0700)
committerLinus Torvalds <torvalds@woody.linux-foundation.org>
Tue, 16 Oct 2007 16:43:09 +0000 (09:43 -0700)
Direct Cache Access (DCA) is a method for warming the CPU cache before data
is used, with the intent of lessening the impact of cache misses.  This
patch adds a manager and interface for matching up client requests for DCA
services with devices that offer DCA services.

In order to use DCA, a module must do bus writes with the appropriate tag
bits set to trigger a cache read for a specific CPU.  However, different
CPUs and chipsets can require different sets of tag bits, and the methods
for determining the correct bits may be simple hardcoding or may be a
hardware specific magic incantation.  This interface is a way for DCA
clients to find the correct tag bits for the targeted CPU without needing
to know the specifics.

    [Dave Miller] use DEFINE_SPINLOCK()

Signed-off-by: Shannon Nelson <shannon.nelson@intel.com>
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
drivers/Kconfig
drivers/Makefile
drivers/dca/Kconfig [new file with mode: 0644]
drivers/dca/Makefile [new file with mode: 0644]
drivers/dca/dca-core.c [new file with mode: 0644]
drivers/dca/dca-sysfs.c [new file with mode: 0644]
include/linux/dca.h [new file with mode: 0644]

index 7bdae47d6b91cea8848d2ce48e401afe9067c921..4fb134d50da731e96ce25aef47c3f3b8c21f45f1 100644 (file)
@@ -84,6 +84,8 @@ source "drivers/rtc/Kconfig"
 
 source "drivers/dma/Kconfig"
 
+source "drivers/dca/Kconfig"
+
 source "drivers/auxdisplay/Kconfig"
 
 source "drivers/kvm/Kconfig"
index a168eacdcd9c1d57333e9da931d26a712ffb01c2..174c27eb443032f06ad3b8a61c7410bd6f0d4566 100644 (file)
@@ -85,6 +85,7 @@ obj-$(CONFIG_CRYPTO)          += crypto/
 obj-$(CONFIG_SUPERH)           += sh/
 obj-$(CONFIG_GENERIC_TIME)     += clocksource/
 obj-$(CONFIG_DMA_ENGINE)       += dma/
+obj-$(CONFIG_DCA)              += dca/
 obj-$(CONFIG_HID)              += hid/
 obj-$(CONFIG_PPC_PS3)          += ps3/
 obj-$(CONFIG_OF)               += of/
diff --git a/drivers/dca/Kconfig b/drivers/dca/Kconfig
new file mode 100644 (file)
index 0000000..e2f7436
--- /dev/null
@@ -0,0 +1,11 @@
+#
+# DCA server configuration
+#
+
+config DCA
+       tristate "DCA support for clients and providers"
+       default m
+       help
+         This is a server to help modules that want to use Direct Cache
+         Access to find DCA providers that will supply correct CPU tags.
+
diff --git a/drivers/dca/Makefile b/drivers/dca/Makefile
new file mode 100644 (file)
index 0000000..b2db56b
--- /dev/null
@@ -0,0 +1,2 @@
+obj-$(CONFIG_DCA) += dca.o
+dca-objs := dca-core.o dca-sysfs.o
diff --git a/drivers/dca/dca-core.c b/drivers/dca/dca-core.c
new file mode 100644 (file)
index 0000000..bf5b92f
--- /dev/null
@@ -0,0 +1,200 @@
+/*
+ * Copyright(c) 2007 Intel Corporation. All rights reserved.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License as published by the Free
+ * Software Foundation; either version 2 of the License, or (at your option)
+ * any later version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
+ * more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program; if not, write to the Free Software Foundation, Inc., 59
+ * Temple Place - Suite 330, Boston, MA  02111-1307, USA.
+ *
+ * The full GNU General Public License is included in this distribution in the
+ * file called COPYING.
+ */
+
+/*
+ * This driver supports an interface for DCA clients and providers to meet.
+ */
+
+#include <linux/kernel.h>
+#include <linux/notifier.h>
+#include <linux/device.h>
+#include <linux/dca.h>
+
+MODULE_LICENSE("GPL");
+
+/* For now we're assuming a single, global, DCA provider for the system. */
+
+static DEFINE_SPINLOCK(dca_lock);
+
+static struct dca_provider *global_dca = NULL;
+
+/**
+ * dca_add_requester - add a dca client to the list
+ * @dev - the device that wants dca service
+ */
+int dca_add_requester(struct device *dev)
+{
+       int err, slot;
+
+       if (!global_dca)
+               return -ENODEV;
+
+       spin_lock(&dca_lock);
+       slot = global_dca->ops->add_requester(global_dca, dev);
+       spin_unlock(&dca_lock);
+       if (slot < 0)
+               return slot;
+
+       err = dca_sysfs_add_req(global_dca, dev, slot);
+       if (err) {
+               spin_lock(&dca_lock);
+               global_dca->ops->remove_requester(global_dca, dev);
+               spin_unlock(&dca_lock);
+               return err;
+       }
+
+       return 0;
+}
+EXPORT_SYMBOL_GPL(dca_add_requester);
+
+/**
+ * dca_remove_requester - remove a dca client from the list
+ * @dev - the device that wants dca service
+ */
+int dca_remove_requester(struct device *dev)
+{
+       int slot;
+       if (!global_dca)
+               return -ENODEV;
+
+       spin_lock(&dca_lock);
+       slot = global_dca->ops->remove_requester(global_dca, dev);
+       spin_unlock(&dca_lock);
+       if (slot < 0)
+               return slot;
+
+       dca_sysfs_remove_req(global_dca, slot);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(dca_remove_requester);
+
+/**
+ * dca_get_tag - return the dca tag for the given cpu
+ * @cpu - the cpuid as returned by get_cpu()
+ */
+u8 dca_get_tag(int cpu)
+{
+       if (!global_dca)
+               return -ENODEV;
+       return global_dca->ops->get_tag(global_dca, cpu);
+}
+EXPORT_SYMBOL_GPL(dca_get_tag);
+
+/**
+ * alloc_dca_provider - get data struct for describing a dca provider
+ * @ops - pointer to struct of dca operation function pointers
+ * @priv_size - size of extra mem to be added for provider's needs
+ */
+struct dca_provider *alloc_dca_provider(struct dca_ops *ops, int priv_size)
+{
+       struct dca_provider *dca;
+       int alloc_size;
+
+       alloc_size = (sizeof(*dca) + priv_size);
+       dca = kzalloc(alloc_size, GFP_KERNEL);
+       if (!dca)
+               return NULL;
+       dca->ops = ops;
+
+       return dca;
+}
+EXPORT_SYMBOL_GPL(alloc_dca_provider);
+
+/**
+ * free_dca_provider - release the dca provider data struct
+ * @ops - pointer to struct of dca operation function pointers
+ * @priv_size - size of extra mem to be added for provider's needs
+ */
+void free_dca_provider(struct dca_provider *dca)
+{
+       kfree(dca);
+}
+EXPORT_SYMBOL_GPL(free_dca_provider);
+
+static BLOCKING_NOTIFIER_HEAD(dca_provider_chain);
+
+/**
+ * register_dca_provider - register a dca provider
+ * @dca - struct created by alloc_dca_provider()
+ * @dev - device providing dca services
+ */
+int register_dca_provider(struct dca_provider *dca, struct device *dev)
+{
+       int err;
+
+       if (global_dca)
+               return -EEXIST;
+       err = dca_sysfs_add_provider(dca, dev);
+       if (err)
+               return err;
+       global_dca = dca;
+       blocking_notifier_call_chain(&dca_provider_chain,
+                                    DCA_PROVIDER_ADD, NULL);
+       return 0;
+}
+EXPORT_SYMBOL_GPL(register_dca_provider);
+
+/**
+ * unregister_dca_provider - remove a dca provider
+ * @dca - struct created by alloc_dca_provider()
+ */
+void unregister_dca_provider(struct dca_provider *dca)
+{
+       if (!global_dca)
+               return;
+       blocking_notifier_call_chain(&dca_provider_chain,
+                                    DCA_PROVIDER_REMOVE, NULL);
+       global_dca = NULL;
+       dca_sysfs_remove_provider(dca);
+}
+EXPORT_SYMBOL_GPL(unregister_dca_provider);
+
+/**
+ * dca_register_notify - register a client's notifier callback
+ */
+void dca_register_notify(struct notifier_block *nb)
+{
+       blocking_notifier_chain_register(&dca_provider_chain, nb);
+}
+EXPORT_SYMBOL_GPL(dca_register_notify);
+
+/**
+ * dca_unregister_notify - remove a client's notifier callback
+ */
+void dca_unregister_notify(struct notifier_block *nb)
+{
+       blocking_notifier_chain_unregister(&dca_provider_chain, nb);
+}
+EXPORT_SYMBOL_GPL(dca_unregister_notify);
+
+static int __init dca_init(void)
+{
+       return dca_sysfs_init();
+}
+
+static void __exit dca_exit(void)
+{
+       dca_sysfs_exit();
+}
+
+module_init(dca_init);
+module_exit(dca_exit);
+
diff --git a/drivers/dca/dca-sysfs.c b/drivers/dca/dca-sysfs.c
new file mode 100644 (file)
index 0000000..24a263b
--- /dev/null
@@ -0,0 +1,88 @@
+#include <linux/kernel.h>
+#include <linux/spinlock.h>
+#include <linux/device.h>
+#include <linux/idr.h>
+#include <linux/kdev_t.h>
+#include <linux/err.h>
+#include <linux/dca.h>
+
+static struct class *dca_class;
+static struct idr dca_idr;
+static spinlock_t dca_idr_lock;
+
+int dca_sysfs_add_req(struct dca_provider *dca, struct device *dev, int slot)
+{
+       struct class_device *cd;
+
+       cd = class_device_create(dca_class, dca->cd, MKDEV(0, slot + 1),
+                                dev, "requester%d", slot);
+       if (IS_ERR(cd))
+               return PTR_ERR(cd);
+       return 0;
+}
+
+void dca_sysfs_remove_req(struct dca_provider *dca, int slot)
+{
+       class_device_destroy(dca_class, MKDEV(0, slot + 1));
+}
+
+int dca_sysfs_add_provider(struct dca_provider *dca, struct device *dev)
+{
+       struct class_device *cd;
+       int err = 0;
+
+idr_try_again:
+       if (!idr_pre_get(&dca_idr, GFP_KERNEL))
+               return -ENOMEM;
+       spin_lock(&dca_idr_lock);
+       err = idr_get_new(&dca_idr, dca, &dca->id);
+       spin_unlock(&dca_idr_lock);
+       switch (err) {
+       case 0:
+               break;
+       case -EAGAIN:
+               goto idr_try_again;
+       default:
+               return err;
+       }
+
+       cd = class_device_create(dca_class, NULL, MKDEV(0, 0),
+                                dev, "dca%d", dca->id);
+       if (IS_ERR(cd)) {
+               spin_lock(&dca_idr_lock);
+               idr_remove(&dca_idr, dca->id);
+               spin_unlock(&dca_idr_lock);
+               return PTR_ERR(cd);
+       }
+       dca->cd = cd;
+       return 0;
+}
+
+void dca_sysfs_remove_provider(struct dca_provider *dca)
+{
+       class_device_unregister(dca->cd);
+       dca->cd = NULL;
+       spin_lock(&dca_idr_lock);
+       idr_remove(&dca_idr, dca->id);
+       spin_unlock(&dca_idr_lock);
+}
+
+int __init dca_sysfs_init(void)
+{
+       idr_init(&dca_idr);
+       spin_lock_init(&dca_idr_lock);
+
+       dca_class = class_create(THIS_MODULE, "dca");
+       if (IS_ERR(dca_class)) {
+               idr_destroy(&dca_idr);
+               return PTR_ERR(dca_class);
+       }
+       return 0;
+}
+
+void __exit dca_sysfs_exit(void)
+{
+       class_destroy(dca_class);
+       idr_destroy(&dca_idr);
+}
+
diff --git a/include/linux/dca.h b/include/linux/dca.h
new file mode 100644 (file)
index 0000000..83eaecc
--- /dev/null
@@ -0,0 +1,47 @@
+#ifndef DCA_H
+#define DCA_H
+/* DCA Provider API */
+
+/* DCA Notifier Interface */
+void dca_register_notify(struct notifier_block *nb);
+void dca_unregister_notify(struct notifier_block *nb);
+
+#define DCA_PROVIDER_ADD     0x0001
+#define DCA_PROVIDER_REMOVE  0x0002
+
+struct dca_provider {
+       struct dca_ops          *ops;
+       struct class_device     *cd;
+       int                      id;
+};
+
+struct dca_ops {
+       int     (*add_requester)    (struct dca_provider *, struct device *);
+       int     (*remove_requester) (struct dca_provider *, struct device *);
+       u8      (*get_tag)          (struct dca_provider *, int cpu);
+};
+
+struct dca_provider *alloc_dca_provider(struct dca_ops *ops, int priv_size);
+void free_dca_provider(struct dca_provider *dca);
+int register_dca_provider(struct dca_provider *dca, struct device *dev);
+void unregister_dca_provider(struct dca_provider *dca);
+
+static inline void *dca_priv(struct dca_provider *dca)
+{
+       return (void *)dca + sizeof(struct dca_provider);
+}
+
+/* Requester API */
+int dca_add_requester(struct device *dev);
+int dca_remove_requester(struct device *dev);
+u8 dca_get_tag(int cpu);
+
+/* internal stuff */
+int __init dca_sysfs_init(void);
+void __exit dca_sysfs_exit(void);
+int dca_sysfs_add_provider(struct dca_provider *dca, struct device *dev);
+void dca_sysfs_remove_provider(struct dca_provider *dca);
+int dca_sysfs_add_req(struct dca_provider *dca, struct device *dev, int slot);
+void dca_sysfs_remove_req(struct dca_provider *dca, int slot);
+
+#endif /* DCA_H */