Mega busdma API commit.

Add two new arguments to bus_dma_tag_create(): lockfunc and lockfuncarg.
Lockfunc allows a driver to provide a function for managing its locking
semantics while using busdma.  At the moment, this is used for the
asynchronous busdma_swi and callback mechanism.  Two lockfunc implementations
are provided: busdma_lock_mutex() performs standard mutex operations on the
mutex that is specified from lockfuncarg.  dftl_lock() is a panic
implementation and is defaulted to when NULL, NULL are passed to
bus_dma_tag_create().  The only time that NULL, NULL should ever be used is
when the driver ensures that bus_dmamap_load() will not be deferred.
Drivers that do not provide their own locking can pass
busdma_lock_mutex,&Giant args in order to preserve the former behaviour.

sparc64 and powerpc do not provide real busdma_swi functions, so this is
largely a noop on those platforms.  The busdma_swi on is64 is not properly
locked yet, so warnings will be emitted on this platform when busdma
callback deferrals happen.

If anyone gets panics or warnings from dflt_lock() being called, please
let me know right away.

Reviewed by:	tmm, gibbs

2 files changed, 68 insertions, 3 deletions

diff --git a/sys/powerpc/include/bus.h b/sys/powerpc/include/bus.h
index eff6e8f..3ee2de5 100644
--- a/sys/powerpc/include/bus.h
+++ b/sys/powerpc/include/bus.h
@@ -797,6 +797,17 @@ typedef struct bus_dma_segment {
 typedef int bus_dma_filter_t(void *, bus_addr_t);
 
 /*
+ * A function that performs driver-specific syncronization on behalf of
+ * busdma.
+ */
+typedef enum {
+	BUS_DMA_LOCK    = 0x01,
+	BUS_DMA_UNLOCK  = 0x02,
+} bus_dma_lock_op_t;
+ 
+typedef void bus_dma_lock_t(void *, bus_dma_lock_op_t);
+   
+/*
  * Allocate a device specific dma_tag encapsulating the constraints of
  * the parent tag in addition to other restrictions specified:
  *
@@ -820,7 +831,8 @@ int bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 		       bus_size_t boundary, bus_addr_t lowaddr,
 		       bus_addr_t highaddr, bus_dma_filter_t *filtfunc,
 		       void *filtfuncarg, bus_size_t maxsize, int nsegments,
-		       bus_size_t maxsegsz, int flags, bus_dma_tag_t *dmat);
+		       bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
+		       void *lockfuncarg, bus_dma_tag_t *dmat);
 
 int bus_dma_tag_destroy(bus_dma_tag_t dmat);
 
@@ -896,4 +908,8 @@ void bus_dmamap_sync(bus_dma_tag_t, bus_dmamap_t, bus_dmasync_op_t);
  */
 void bus_dmamap_unload(bus_dma_tag_t dmat, bus_dmamap_t map);
 
+/*
+ * Generic helper function for manipulating mutexes.
+ */     
+void busdma_lock_mutex(void *arg, bus_dma_lock_op_t op);
 #endif /* _MACPPC_BUS_H_ */
diff --git a/sys/powerpc/powerpc/busdma_machdep.c b/sys/powerpc/powerpc/busdma_machdep.c
index 3d6d402..f3ef3e3 100644
--- a/sys/powerpc/powerpc/busdma_machdep.c
+++ b/sys/powerpc/powerpc/busdma_machdep.c
@@ -67,6 +67,8 @@ struct bus_dma_tag {
 	int               flags;
 	int               ref_count;
 	int               map_count;
+	bus_dma_lock_t	 *lockfunc;
+	void		 *lockfuncarg;
 };
 
 struct bus_dmamap {
@@ -75,10 +77,49 @@ struct bus_dmamap {
         bus_size_t             buflen;          /* unmapped buffer length */
         bus_dmamap_callback_t *callback;
         void                  *callback_arg;
-	struct mtx	      *callback_mtx;
 };
 
 /*
+ * Convenience function for manipulating driver locks from busdma (during
+ * busdma_swi, for example).  Drivers that don't provide their own locks
+ * should specify &Giant to dmat->lockfuncarg.  Drivers that use their own
+ * non-mutex locking scheme don't have to use this at all.
+ */
+void
+busdma_lock_mutex(void *arg, bus_dma_lock_op_t op)
+{
+	struct mtx *dmtx;
+
+	dmtx = (struct mtx *)arg;
+	switch (op) {
+	case BUS_DMA_LOCK:
+		mtx_lock(dmtx);
+		break;
+	case BUS_DMA_UNLOCK:
+		mtx_unlock(dmtx);
+		break;
+	default:
+		panic("Unknown operation 0x%x for busdma_lock_mutex!", op);
+	}
+}
+
+/*
+ * dflt_lock should never get called.  It gets put into the dma tag when
+ * lockfunc == NULL, which is only valid if the maps that are associated
+ * with the tag are meant to never be defered.
+ * XXX Should have a way to identify which driver is responsible here.
+ */
+static void
+dflt_lock(void *arg, bus_dma_lock_op_t op)
+{
+#ifdef INVARIANTS
+	panic("driver error: busdma dflt_lock called");
+#else
+	printf("DRIVER_ERROR: busdma dflt_lock called\n");
+#endif
+}
+
+/*
  * Allocate a device specific dma_tag.
  */
 int
@@ -86,7 +127,8 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 		   bus_size_t boundary, bus_addr_t lowaddr,
 		   bus_addr_t highaddr, bus_dma_filter_t *filter,
 		   void *filterarg, bus_size_t maxsize, int nsegments,
-		   bus_size_t maxsegsz, int flags, bus_dma_tag_t *dmat)
+		   bus_size_t maxsegsz, int flags, bus_dma_lock_t *lockfunc,
+		   void *lockfuncarg, bus_dma_tag_t *dmat)
 {
 	bus_dma_tag_t newtag;
 	int error = 0;
@@ -111,6 +153,13 @@ bus_dma_tag_create(bus_dma_tag_t parent, bus_size_t alignment,
 	newtag->flags = flags;
 	newtag->ref_count = 1; /* Count ourself */
 	newtag->map_count = 0;
+	if (lockfunc != NULL) {
+		newtag->lockfunc = lockfunc;
+		newtag->lockfuncarg = lockfuncarg;
+	} else {
+		newtag->lockfunc = dflt_lock;
+		newtag->lockfuncarg = NULL;
+	}
 
         /*
 	 * Take into account any restrictions imposed by our parent tag