7589670f37
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>
88 lines
1.8 KiB
C
88 lines
1.8 KiB
C
#include <linux/kernel.h>
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#include <linux/spinlock.h>
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#include <linux/device.h>
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#include <linux/idr.h>
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#include <linux/kdev_t.h>
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#include <linux/err.h>
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#include <linux/dca.h>
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static struct class *dca_class;
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static struct idr dca_idr;
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static spinlock_t dca_idr_lock;
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int dca_sysfs_add_req(struct dca_provider *dca, struct device *dev, int slot)
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{
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struct class_device *cd;
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cd = class_device_create(dca_class, dca->cd, MKDEV(0, slot + 1),
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dev, "requester%d", slot);
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if (IS_ERR(cd))
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return PTR_ERR(cd);
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return 0;
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}
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void dca_sysfs_remove_req(struct dca_provider *dca, int slot)
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{
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class_device_destroy(dca_class, MKDEV(0, slot + 1));
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}
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int dca_sysfs_add_provider(struct dca_provider *dca, struct device *dev)
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{
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struct class_device *cd;
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int err = 0;
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idr_try_again:
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if (!idr_pre_get(&dca_idr, GFP_KERNEL))
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return -ENOMEM;
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spin_lock(&dca_idr_lock);
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err = idr_get_new(&dca_idr, dca, &dca->id);
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spin_unlock(&dca_idr_lock);
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switch (err) {
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case 0:
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break;
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case -EAGAIN:
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goto idr_try_again;
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default:
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return err;
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}
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cd = class_device_create(dca_class, NULL, MKDEV(0, 0),
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dev, "dca%d", dca->id);
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if (IS_ERR(cd)) {
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spin_lock(&dca_idr_lock);
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idr_remove(&dca_idr, dca->id);
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spin_unlock(&dca_idr_lock);
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return PTR_ERR(cd);
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}
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dca->cd = cd;
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return 0;
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}
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void dca_sysfs_remove_provider(struct dca_provider *dca)
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{
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class_device_unregister(dca->cd);
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dca->cd = NULL;
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spin_lock(&dca_idr_lock);
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idr_remove(&dca_idr, dca->id);
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spin_unlock(&dca_idr_lock);
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}
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int __init dca_sysfs_init(void)
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{
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idr_init(&dca_idr);
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spin_lock_init(&dca_idr_lock);
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dca_class = class_create(THIS_MODULE, "dca");
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if (IS_ERR(dca_class)) {
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idr_destroy(&dca_idr);
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return PTR_ERR(dca_class);
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}
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return 0;
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}
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void __exit dca_sysfs_exit(void)
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{
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class_destroy(dca_class);
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idr_destroy(&dca_idr);
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}
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