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: 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>

1 files changed, 47 insertions, 0 deletions

diff --git a/include/linux/dca.h b/include/linux/dca.h
new file mode 100644
index 000000000000..83eaecc6f8ab
--- /dev/null
+++ b/include/linux/dca.h
@@ -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 */