common: rework bouncebuf implementation

The current bouncebuf API requires all parameters to be passed to both
bounce_buffer_start() and bounce_buffer_stop(). Modify the bouncebuf
start function to accept a state structure as a parameter, and only
require that state struct to be passed to the stop function. This
simplifies usage of the bounce buffer by clients.

Don't modify the data pointer, but rather store the temporary buffer in
this state struct. The bouncebuf code ensures that client code can
always use a single buffer pointer in the state structure, irrespective
of whether a bounce buffer actually had to be allocated.

Move cache management logic into the bounce buffer code, so that each
client doesn't have to duplicate this. I believe there's no need to
invalidate the buffer before a DMA operation, since flushing the cache
should prevent any write-backs.

Update the MXS MMC driver for this change.

Signed-off-by: Stephen Warren <swarren@nvidia.com>
Acked-by: Simon Glass <sjg@chromium.org>
Tested-by: Simon Glass <sjg@chromium.org>
Signed-off-by: Andy Fleming <afleming@freescale.com>

1 files changed, 41 insertions, 34 deletions

diff --git a/common/bouncebuf.c b/common/bouncebuf.c
index 4f827f8..1df12cd 100644
--- a/common/bouncebuf.c
+++ b/common/bouncebuf.c
@@ -27,21 +27,19 @@
 #include <errno.h>
 #include <bouncebuf.h>
 
-static int addr_aligned(void *data, size_t len)
+static int addr_aligned(struct bounce_buffer *state)
 {
 	const ulong align_mask = ARCH_DMA_MINALIGN - 1;
 
 	/* Check if start is aligned */
-	if ((ulong)data & align_mask) {
-		debug("Unaligned start address %p\n", data);
+	if ((ulong)state->user_buffer & align_mask) {
+		debug("Unaligned buffer address %p\n", state->user_buffer);
 		return 0;
 	}
 
-	data += len;
-
-	/* Check if end is aligned */
-	if ((ulong)data & align_mask) {
-		debug("Unaligned end address %p\n", data);
+	/* Check if length is aligned */
+	if (state->len != state->len_aligned) {
+		debug("Unaligned buffer length %d\n", state->len);
 		return 0;
 	}
 
@@ -49,44 +47,53 @@ static int addr_aligned(void *data, size_t len)
 	return 1;
 }
 
-int bounce_buffer_start(void **data, size_t len, void **backup, uint8_t flags)
+int bounce_buffer_start(struct bounce_buffer *state, void *data,
+			size_t len, unsigned int flags)
 {
-	void *tmp;
-	size_t alen;
-
-	if (addr_aligned(*data, len)) {
-		*backup = NULL;
-		return 0;
+	state->user_buffer = data;
+	state->bounce_buffer = data;
+	state->len = len;
+	state->len_aligned = roundup(len, ARCH_DMA_MINALIGN);
+	state->flags = flags;
+
+	if (!addr_aligned(state)) {
+		state->bounce_buffer = memalign(ARCH_DMA_MINALIGN,
+						state->len_aligned);
+		if (!state->bounce_buffer)
+			return -ENOMEM;
+
+		if (state->flags & GEN_BB_READ)
+			memcpy(state->bounce_buffer, state->user_buffer,
+				state->len);
 	}
 
-	alen = roundup(len, ARCH_DMA_MINALIGN);
-	tmp = memalign(ARCH_DMA_MINALIGN, alen);
-
-	if (!tmp)
-		return -ENOMEM;
-
-	if (flags & GEN_BB_READ)
-		memcpy(tmp, *data, len);
-
-	*backup = *data;
-	*data = tmp;
+	/*
+	 * Flush data to RAM so DMA reads can pick it up,
+	 * and any CPU writebacks don't race with DMA writes
+	 */
+	flush_dcache_range((unsigned long)state->bounce_buffer,
+				(unsigned long)(state->bounce_buffer) +
+					state->len_aligned);
 
 	return 0;
 }
 
-int bounce_buffer_stop(void **data, size_t len, void **backup, uint8_t flags)
+int bounce_buffer_stop(struct bounce_buffer *state)
 {
-	void *tmp = *data;
+	if (state->flags & GEN_BB_WRITE) {
+		/* Invalidate cache so that CPU can see any newly DMA'd data */
+		invalidate_dcache_range((unsigned long)state->bounce_buffer,
+					(unsigned long)(state->bounce_buffer) +
+						state->len_aligned);
+	}
 
-	/* The buffer was already aligned, since "backup" is NULL. */
-	if (!*backup)
+	if (state->bounce_buffer == state->user_buffer)
 		return 0;
 
-	if (flags & GEN_BB_WRITE)
-		memcpy(*backup, *data, len);
+	if (state->flags & GEN_BB_WRITE)
+		memcpy(state->user_buffer, state->bounce_buffer, state->len);
 
-	*data = *backup;
-	free(tmp);
+	free(state->bounce_buffer);
 
 	return 0;
 }