[PATCH 2/2] scsi: Add buffer_aligned check pass-through

[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. This is
a pass-through callback from block uclass to drivers.

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/scsi/scsi.c | 15 +++++++++++++++
 include/scsi.h      | 19 +++++++++++++++++++
 2 files changed, 34 insertions(+)

diff --git a/drivers/scsi/scsi.c b/drivers/scsi/scsi.c
index 6498f998ad6..7411660d465 100644
--- a/drivers/scsi/scsi.c
+++ b/drivers/scsi/scsi.c
@@ -274,6 +274,18 @@ static ulong scsi_write(struct udevice *dev, lbaint_t blknr, lbaint_t blkcnt,
 	      __func__, start, smallblks, buf_addr);
 	return blkcnt;
 }
+
+#if IS_ENABLED(CONFIG_BOUNCE_BUFFER)
+static int scsi_buffer_aligned(struct udevice *dev, struct bounce_buffer *state)
+{
+	struct scsi_ops *ops = scsi_get_ops(dev->parent);
+
+	if (ops->buffer_aligned)
+		return ops->buffer_aligned(dev->parent, state);
+
+	return 1;
+}
+#endif	/* CONFIG_BOUNCE_BUFFER */
 #endif
 
 #if defined(CONFIG_PCI) && !defined(CONFIG_SCSI_AHCI_PLAT) && \
@@ -720,6 +732,9 @@ int scsi_scan(bool verbose)
 static const struct blk_ops scsi_blk_ops = {
 	.read	= scsi_read,
 	.write	= scsi_write,
+#if IS_ENABLED(CONFIG_BOUNCE_BUFFER)
+	.buffer_aligned	= scsi_buffer_aligned,
+#endif	/* CONFIG_BOUNCE_BUFFER */
 };
 
 U_BOOT_DRIVER(scsi_blk) = {
diff --git a/include/scsi.h b/include/scsi.h
index 9efefea99bb..ee9d622680d 100644
--- a/include/scsi.h
+++ b/include/scsi.h
@@ -7,6 +7,7 @@
  #define _SCSI_H
 
 #include <asm/cache.h>
+#include <bouncebuf.h>
 #include <linux/dma-direction.h>
 
 /* Fix this to the maximum */
@@ -298,6 +299,24 @@ struct scsi_ops {
 	 * @return 0 if OK, -ve on error
 	 */
 	int (*bus_reset)(struct udevice *dev);
+
+#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 */
 };
 
 #define scsi_get_ops(dev)        ((struct scsi_ops *)(dev)->driver->ops)
-- 
2.40.1