Add some CACHEALIGN_* macros and a helper function to assist in aligning data and buffers on PortalPlayer processors to cache line boundaries. They're noops when PROC_NEED_CACHEALIGN isn't defined. Go safe and increase the value to 32 since I'm not sure yet if 16 is sufficient - changing that is a one-liner. Add helper to plugin API which will be needed shortly.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@15523 a1c6a512-1295-4272-9138-f99709370657

firmware/general.c

@@ -17,6 +17,7 @@
  *
  ****************************************************************************/
 #include <limits.h>
+#include "system.h"
 #include "config.h"
 #include "general.h"
 
@@ -75,3 +76,26 @@ int make_list_from_caps32(unsigned long src_mask,
 
     return count;
 } /* make_list_from_caps32 */
+
+/* Only needed for cache aligning atm */
+#ifdef PROC_NEEDS_CACHEALIGN
+/* Align a buffer and size to a size boundary while remaining within
+ * the original boundaries */
+size_t align_buffer(void **start, size_t size, size_t align)
+{
+    void *newstart = *start;
+    void *newend = newstart + size;
+
+    /* Align the end down and the start up */
+    newend = (void *)ALIGN_DOWN((intptr_t)newend, align);
+    newstart = (void *)ALIGN_UP((intptr_t)newstart, align);
+
+    /* Hmmm - too small for this */
+    if (newend <= newstart)
+        return 0;
+
+    /* Return adjusted pointer and size */
+    *start = newstart;
+    return newend - newstart;
+}
+#endif /* PROC_NEEDS_CACHEALIGN */