Commit 7589670f authored by Shannon Nelson's avatar Shannon Nelson Committed by Linus Torvalds

DCA: Add Direct Cache Access driver

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: default avatarShannon Nelson <shannon.nelson@intel.com>
Acked-by: default avatarDavid S. Miller <davem@davemloft.net>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent 3e037454
......@@ -84,6 +84,8 @@ source "drivers/rtc/Kconfig"
source "drivers/dma/Kconfig"
source "drivers/dca/Kconfig"
source "drivers/auxdisplay/Kconfig"
source "drivers/kvm/Kconfig"
......
......@@ -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/
......
#
# 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.
obj-$(CONFIG_DCA) += dca.o
dca-objs := dca-core.o dca-sysfs.o
/*
* 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);
#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);
}
#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 */
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