[U-Boot] [PATCH v2] common: usb_storage : Implement logic to calculate optimal usb maximum trasfer blocks

[Rajesh Bhagat]

Implements the logic to calculate the optimal usb maximum trasfer blocks
instead of sending USB_MAX_XFER_BLK blocks which is 65535 and 20 in case
of EHCI and other USB protocols respectively.

It defines USB_MIN_XFER_BLK/USB_MAX_XFER_BLK trasfer blocks that should
be checked for success starting from minimum to maximum, and rest of the
read/write are performed with that optimal value. It tries to increase/
decrease the blocks in follwing scenarios:

1.decrease blocks: when read/write for a particular number of blocks
fails.
2. increase blocks: when read/write for a particular number of blocks
pass and amount left to trasfer is greater than current number of
blocks.

Currently changes are done for EHCI where min = 4096 and max = 65535
is taken. And for other cases code is left unchanged by keeping min
= max = 20.

Signed-off-by: Sriram Dash <sriram.dash at nxp.com>
Signed-off-by: Rajesh Bhagat <rajesh.bhagat at nxp.com>
---
 common/usb_storage.c | 71 +++++++++++++++++++++++++++++++++++++++++++---------
 1 file changed, 59 insertions(+), 12 deletions(-)

diff --git a/common/usb_storage.c b/common/usb_storage.c
index 7e6e52d..eee8f4c 100644
--- a/common/usb_storage.c
+++ b/common/usb_storage.c
@@ -106,10 +106,13 @@ struct us_data {
  * enough free heap space left, but the SCSI READ(10) and WRITE(10) commands are
  * limited to 65535 blocks.
  */
+#define USB_MIN_XFER_BLK	4095
 #define USB_MAX_XFER_BLK	65535
 #else
+#define USB_MIN_XFER_BLK	20
 #define USB_MAX_XFER_BLK	20
 #endif
+#define USB_CUR_XFER_BLK(n)	(n >= 0 ? ((1 << (12 + (n))) - 1) : 0)
 
 #ifndef CONFIG_BLK
 static struct us_data usb_stor[USB_MAX_STOR_DEV];
@@ -1117,11 +1120,13 @@ static unsigned long usb_stor_read(struct blk_desc *block_dev, lbaint_t blknr,
 	unsigned short smallblks;
 	struct usb_device *udev;
 	struct us_data *ss;
-	int retry;
+	int retry, pos = 0;
+	bool retry_flag = false;
 	ccb *srb = &usb_ccb;
 #ifdef CONFIG_BLK
 	struct blk_desc *block_dev;
 #endif
+	unsigned short usb_cur_xfer_blk = USB_CUR_XFER_BLK(pos);
 
 	if (blkcnt == 0)
 		return 0;
@@ -1153,26 +1158,46 @@ static unsigned long usb_stor_read(struct blk_desc *block_dev, lbaint_t blknr,
 		/* XXX need some comment here */
 		retry = 2;
 		srb->pdata = (unsigned char *)buf_addr;
-		if (blks > USB_MAX_XFER_BLK)
-			smallblks = USB_MAX_XFER_BLK;
+		if (blks > usb_cur_xfer_blk)
+			smallblks = usb_cur_xfer_blk;
 		else
 			smallblks = (unsigned short) blks;
 retry_it:
-		if (smallblks == USB_MAX_XFER_BLK)
+		debug("usb_read: retry #%d, usb_cur_xfer_blk %hu, smallblks %hu\n",
+		      retry, usb_cur_xfer_blk, smallblks);
+		if (smallblks == usb_cur_xfer_blk)
 			usb_show_progress();
 		srb->datalen = block_dev->blksz * smallblks;
 		srb->pdata = (unsigned char *)buf_addr;
 		if (usb_read_10(srb, ss, start, smallblks)) {
 			debug("Read ERROR\n");
 			usb_request_sense(srb, ss);
-			if (retry--)
+			if (retry--) {
+				/* decrease the usb_cur_xfer_blk */
+				unsigned short size = USB_CUR_XFER_BLK(pos - 1);
+				if (size >= USB_MIN_XFER_BLK) {
+					smallblks = size;
+					usb_cur_xfer_blk = smallblks;
+					pos--;
+				}
+				retry_flag = true;
 				goto retry_it;
+			}
 			blkcnt -= blks;
 			break;
 		}
 		start += smallblks;
 		blks -= smallblks;
 		buf_addr += srb->datalen;
+
+		/* try to increase the usb_cur_xfer_blk */
+		if (!retry_flag) {
+			unsigned short size = USB_CUR_XFER_BLK(pos + 1);
+			if (size <= blks && size <= USB_MAX_XFER_BLK) {
+				usb_cur_xfer_blk = size;
+				pos++;
+			}
+		}
 	} while (blks != 0);
 	ss->flags &= ~USB_READY;
 
@@ -1181,7 +1206,7 @@ retry_it:
 	      start, smallblks, buf_addr);
 
 	usb_disable_asynch(0); /* asynch transfer allowed */
-	if (blkcnt >= USB_MAX_XFER_BLK)
+	if (blkcnt >= usb_cur_xfer_blk)
 		debug("\n");
 	return blkcnt;
 }
@@ -1199,11 +1224,13 @@ static unsigned long usb_stor_write(struct blk_desc *block_dev, lbaint_t blknr,
 	unsigned short smallblks;
 	struct usb_device *udev;
 	struct us_data *ss;
-	int retry;
+	int retry, pos = 0;
+	bool retry_flag = false;
 	ccb *srb = &usb_ccb;
 #ifdef CONFIG_BLK
 	struct blk_desc *block_dev;
 #endif
+	unsigned short usb_cur_xfer_blk = USB_CUR_XFER_BLK(pos);
 
 	if (blkcnt == 0)
 		return 0;
@@ -1239,26 +1266,46 @@ static unsigned long usb_stor_write(struct blk_desc *block_dev, lbaint_t blknr,
 		 */
 		retry = 2;
 		srb->pdata = (unsigned char *)buf_addr;
-		if (blks > USB_MAX_XFER_BLK)
-			smallblks = USB_MAX_XFER_BLK;
+		if (blks > usb_cur_xfer_blk)
+			smallblks = usb_cur_xfer_blk;
 		else
 			smallblks = (unsigned short) blks;
 retry_it:
-		if (smallblks == USB_MAX_XFER_BLK)
+		debug("usb_write: retry #%d, usb_cur_xfer_blk %hu, smallblks %hu\n",
+		      retry, usb_cur_xfer_blk, smallblks);
+		if (smallblks == usb_cur_xfer_blk)
 			usb_show_progress();
 		srb->datalen = block_dev->blksz * smallblks;
 		srb->pdata = (unsigned char *)buf_addr;
 		if (usb_write_10(srb, ss, start, smallblks)) {
 			debug("Write ERROR\n");
 			usb_request_sense(srb, ss);
-			if (retry--)
+			if (retry--) {
+				/* decrease the usb_cur_xfer_blk */
+				unsigned short size = USB_CUR_XFER_BLK(pos - 1);
+				if (size >= USB_MIN_XFER_BLK) {
+					smallblks = size;
+					usb_cur_xfer_blk = smallblks;
+					pos--;
+				}
+				retry_flag = true;
 				goto retry_it;
+			}
 			blkcnt -= blks;
 			break;
 		}
 		start += smallblks;
 		blks -= smallblks;
 		buf_addr += srb->datalen;
+
+		/* try to increase the usb_cur_xfer_blk */
+		if (!retry_flag) {
+			unsigned short size = USB_CUR_XFER_BLK(pos + 1);
+			if (size <= blks && size <= USB_MAX_XFER_BLK) {
+				usb_cur_xfer_blk = size;
+				pos++;
+			}
+		}
 	} while (blks != 0);
 	ss->flags &= ~USB_READY;
 
@@ -1266,7 +1313,7 @@ retry_it:
 	      PRIxPTR "\n", start, smallblks, buf_addr);
 
 	usb_disable_asynch(0); /* asynch transfer allowed */
-	if (blkcnt >= USB_MAX_XFER_BLK)
+	if (blkcnt >= usb_cur_xfer_blk)
 		debug("\n");
 	return blkcnt;
 
-- 
2.6.2.198.g614a2ac