[PATCH 1/2] blk: Add bounce buffer support to read/write operations

[Marek Vasut]

Some devices have limited DMA capabilities and require that the
buffers passed to them fit specific properties. Add new optional
callback which can be used at driver level to indicate whether a
buffer alignment is suitable for the device DMA or not, and
trigger use of generic bounce buffer implementation to help use
of unsuitable buffers at the expense of performance degradation.

Signed-off-by: Marek Vasut <marek.vasut+renesas at mailbox.org>
---
Cc: Abdellatif El Khlifi <abdellatif.elkhlifi at arm.com>
Cc: Bin Meng <bmeng.cn at gmail.com>
Cc: Heinrich Schuchardt <xypron.glpk at gmx.de>
Cc: Mattijs Korpershoek <mkorpershoek at baylibre.com>
Cc: Michal Suchanek <msuchanek at suse.de>
Cc: Simon Glass <sjg at chromium.org>
Cc: Tobias Waldekranz <tobias at waldekranz.com>
---
 drivers/block/blk-uclass.c | 62 ++++++++++++++++++++++++++++++++++++--
 include/blk.h              | 19 ++++++++++++
 2 files changed, 79 insertions(+), 2 deletions(-)

diff --git a/drivers/block/blk-uclass.c b/drivers/block/blk-uclass.c
index 6aac92d9962..885513893f6 100644
--- a/drivers/block/blk-uclass.c
+++ b/drivers/block/blk-uclass.c
@@ -446,6 +446,26 @@ int blk_get_device(int uclass_id, int devnum, struct udevice **devp)
 	return device_probe(*devp);
 }
 
+struct blk_bounce_buffer {
+	struct udevice		*dev;
+	struct bounce_buffer	state;
+};
+
+static int blk_buffer_aligned(struct bounce_buffer *state)
+{
+#if IS_ENABLED(CONFIG_BOUNCE_BUFFER)
+	struct blk_bounce_buffer *bbstate =
+		container_of(state, struct blk_bounce_buffer, state);
+	struct udevice *dev = bbstate->dev;
+	const struct blk_ops *ops = blk_get_ops(dev);
+
+	if (ops->buffer_aligned)
+		return ops->buffer_aligned(dev, state);
+#endif	/* CONFIG_BOUNCE_BUFFER */
+
+	return 1;	/* Default, any buffer is OK */
+}
+
 long blk_read(struct udevice *dev, lbaint_t start, lbaint_t blkcnt, void *buf)
 {
 	struct blk_desc *desc = dev_get_uclass_plat(dev);
@@ -458,7 +478,25 @@ long blk_read(struct udevice *dev, lbaint_t start, lbaint_t blkcnt, void *buf)
 	if (blkcache_read(desc->uclass_id, desc->devnum,
 			  start, blkcnt, desc->blksz, buf))
 		return blkcnt;
-	blks_read = ops->read(dev, start, blkcnt, buf);
+
+	if (IS_ENABLED(CONFIG_BOUNCE_BUFFER)) {
+		struct blk_bounce_buffer bbstate = { .dev = dev };
+		int ret;
+
+		ret = bounce_buffer_start_extalign(&bbstate.state, buf,
+						   blkcnt * desc->blksz,
+						   GEN_BB_WRITE, desc->blksz,
+						   blk_buffer_aligned);
+		if (ret)
+			return ret;
+
+		blks_read = ops->read(dev, start, blkcnt, bbstate.state.bounce_buffer);
+
+		bounce_buffer_stop(&bbstate.state);
+	} else {
+		blks_read = ops->read(dev, start, blkcnt, buf);
+	}
+
 	if (blks_read == blkcnt)
 		blkcache_fill(desc->uclass_id, desc->devnum, start, blkcnt,
 			      desc->blksz, buf);
@@ -471,13 +509,33 @@ long blk_write(struct udevice *dev, lbaint_t start, lbaint_t blkcnt,
 {
 	struct blk_desc *desc = dev_get_uclass_plat(dev);
 	const struct blk_ops *ops = blk_get_ops(dev);
+	long blks_written;
 
 	if (!ops->write)
 		return -ENOSYS;
 
 	blkcache_invalidate(desc->uclass_id, desc->devnum);
 
-	return ops->write(dev, start, blkcnt, buf);
+	if (IS_ENABLED(CONFIG_BOUNCE_BUFFER)) {
+		struct blk_bounce_buffer bbstate = { .dev = dev };
+		int ret;
+
+		ret = bounce_buffer_start_extalign(&bbstate.state, (void *)buf,
+						   blkcnt * desc->blksz,
+						   GEN_BB_READ, desc->blksz,
+						   blk_buffer_aligned);
+		if (ret)
+			return ret;
+
+		blks_written = ops->write(dev, start, blkcnt,
+					  bbstate.state.bounce_buffer);
+
+		bounce_buffer_stop(&bbstate.state);
+	} else {
+		blks_written = ops->write(dev, start, blkcnt, buf);
+	}
+
+	return blks_written;
 }
 
 long blk_erase(struct udevice *dev, lbaint_t start, lbaint_t blkcnt)
diff --git a/include/blk.h b/include/blk.h
index 8986e953e5a..b819f97c2f1 100644
--- a/include/blk.h
+++ b/include/blk.h
@@ -7,6 +7,7 @@
 #ifndef BLK_H
 #define BLK_H
 
+#include <bouncebuf.h>
 #include <dm/uclass-id.h>
 #include <efi.h>
 
@@ -260,6 +261,24 @@ struct blk_ops {
 	 * @return 0 if OK, -ve on error
 	 */
 	int (*select_hwpart)(struct udevice *dev, int hwpart);
+
+#if IS_ENABLED(CONFIG_BOUNCE_BUFFER)
+	/**
+	 * buffer_aligned() - test memory alignment of block operation buffer
+	 *
+	 * Some devices have limited DMA capabilities and require that the
+	 * buffers passed to them fit specific properties. This optional
+	 * callback can be used to indicate whether a buffer alignment is
+	 * suitable for the device DMA or not, and trigger use of generic
+	 * bounce buffer implementation to help use of unsuitable buffers
+	 * at the expense of performance degradation.
+	 *
+	 * @dev:	Block device associated with the request
+	 * @state:	Bounce buffer state
+	 * @return 1 if OK, 0 if unaligned
+	 */
+	int (*buffer_aligned)(struct udevice *dev, struct bounce_buffer *state);
+#endif	/* CONFIG_BOUNCE_BUFFER */
 };
 
 /*
-- 
2.40.1