[U-Boot] [PATCH v2 2/5] ehci-hcd: Boost transfer speed

[Benoît Thébaudeau]

This patch takes advantage of the hardware EHCI qTD queuing mechanism to avoid
software overhead and to make transfers as fast as possible.

The only drawback is a call to memalign. However, this is fast compared to the
transfer timings, and the heap size to allocate is small, e.g. a little bit more
than 100 kB for a transfer length of 65535 packets of 512 bytes.

Tested on i.MX25 and i.MX35. In my test conditions, the speedup was about 15x
using page-aligned buffers, which is really appreciable when accessing large
files.

Signed-off-by: Benoît Thébaudeau <benoit.thebaudeau at advansee.com>
Cc: Marek Vasut <marex at denx.de>
Cc: Ilya Yanok <ilya.yanok at cogentembedded.com>
Cc: Stefan Herbrechtsmeier <stefan at herbrechtsmeier.net>
---
Changes for v2:
 - Use DIV_ROUND_UP to make code more readable.

 .../drivers/usb/host/ehci-hcd.c                    |   92 ++++++++++++++------
 1 file changed, 63 insertions(+), 29 deletions(-)

diff --git u-boot-usb-1b4bd0e.orig/drivers/usb/host/ehci-hcd.c u-boot-usb-1b4bd0e/drivers/usb/host/ehci-hcd.c
index 5b3b906..cf9ab92 100644
--- u-boot-usb-1b4bd0e.orig/drivers/usb/host/ehci-hcd.c
+++ u-boot-usb-1b4bd0e/drivers/usb/host/ehci-hcd.c
@@ -208,7 +208,8 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 		   int length, struct devrequest *req)
 {
 	ALLOC_ALIGN_BUFFER(struct QH, qh, 1, USB_DMA_MINALIGN);
-	ALLOC_ALIGN_BUFFER(struct qTD, qtd, 3, USB_DMA_MINALIGN);
+	struct qTD *qtd;
+	int qtd_count = 0;
 	int qtd_counter = 0;
 
 	volatile struct qTD *vtd;
@@ -229,8 +230,23 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 		      le16_to_cpu(req->value), le16_to_cpu(req->value),
 		      le16_to_cpu(req->index));
 
+	if (req != NULL)			/* SETUP + ACK */
+		qtd_count += 1 + 1;
+	if (length > 0 || req == NULL) {	/* buffer */
+		if ((uint32_t)buffer & 4095)		/* page-unaligned */
+			qtd_count += DIV_ROUND_UP(((uint32_t)buffer & 4095) +
+					length, (QT_BUFFER_CNT - 1) * 4096);
+		else					/* page-aligned */
+			qtd_count += DIV_ROUND_UP(length, QT_BUFFER_CNT * 4096);
+	}
+	qtd = memalign(USB_DMA_MINALIGN, qtd_count * sizeof(struct qTD));
+	if (qtd == NULL) {
+		printf("unable to allocate TDs\n");
+		return -1;
+	}
+
 	memset(qh, 0, sizeof(struct QH));
-	memset(qtd, 0, 3 * sizeof(*qtd));
+	memset(qtd, 0, qtd_count * sizeof(*qtd));
 
 	toggle = usb_gettoggle(dev, usb_pipeendpoint(pipe), usb_pipeout(pipe));
 
@@ -291,31 +307,46 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 	}
 
 	if (length > 0 || req == NULL) {
-		/*
-		 * Setup request qTD (3.5 in ehci-r10.pdf)
-		 *
-		 *   qt_next ................ 03-00 H
-		 *   qt_altnext ............. 07-04 H
-		 *   qt_token ............... 0B-08 H
-		 *
-		 *   [ buffer, buffer_hi ] loaded with "buffer".
-		 */
-		qtd[qtd_counter].qt_next = cpu_to_hc32(QT_NEXT_TERMINATE);
-		qtd[qtd_counter].qt_altnext = cpu_to_hc32(QT_NEXT_TERMINATE);
-		token = (toggle << 31) |
-		    (length << 16) |
-		    ((req == NULL ? 1 : 0) << 15) |
-		    (0 << 12) |
-		    (3 << 10) |
-		    ((usb_pipein(pipe) ? 1 : 0) << 8) | (0x80 << 0);
-		qtd[qtd_counter].qt_token = cpu_to_hc32(token);
-		if (ehci_td_buffer(&qtd[qtd_counter], buffer, length) != 0) {
-			printf("unable construct DATA td\n");
-			goto fail;
-		}
-		/* Update previous qTD! */
-		*tdp = cpu_to_hc32((uint32_t)&qtd[qtd_counter]);
-		tdp = &qtd[qtd_counter++].qt_next;
+		uint8_t *buf_ptr = buffer;
+		int left_length = length;
+
+		do {
+			int xfr_bytes = min(left_length,
+					    (QT_BUFFER_CNT * 4096 -
+					     ((uint32_t)buf_ptr & 4095)) &
+					    ~4095);
+
+			/*
+			 * Setup request qTD (3.5 in ehci-r10.pdf)
+			 *
+			 *   qt_next ................ 03-00 H
+			 *   qt_altnext ............. 07-04 H
+			 *   qt_token ............... 0B-08 H
+			 *
+			 *   [ buffer, buffer_hi ] loaded with "buffer".
+			 */
+			qtd[qtd_counter].qt_next =
+					cpu_to_hc32(QT_NEXT_TERMINATE);
+			qtd[qtd_counter].qt_altnext =
+					cpu_to_hc32(QT_NEXT_TERMINATE);
+			token = (toggle << 31) |
+			    (xfr_bytes << 16) |
+			    ((req == NULL ? 1 : 0) << 15) |
+			    (0 << 12) |
+			    (3 << 10) |
+			    ((usb_pipein(pipe) ? 1 : 0) << 8) | (0x80 << 0);
+			qtd[qtd_counter].qt_token = cpu_to_hc32(token);
+			if (ehci_td_buffer(&qtd[qtd_counter], buf_ptr,
+						xfr_bytes) != 0) {
+				printf("unable construct DATA td\n");
+				goto fail;
+			}
+			/* Update previous qTD! */
+			*tdp = cpu_to_hc32((uint32_t)&qtd[qtd_counter]);
+			tdp = &qtd[qtd_counter++].qt_next;
+			buf_ptr += xfr_bytes;
+			left_length -= xfr_bytes;
+		} while (left_length > 0);
 	}
 
 	if (req != NULL) {
@@ -346,7 +377,8 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 	flush_dcache_range((uint32_t)qh_list,
 		ALIGN_END_ADDR(struct QH, qh_list, 1));
 	flush_dcache_range((uint32_t)qh, ALIGN_END_ADDR(struct QH, qh, 1));
-	flush_dcache_range((uint32_t)qtd, ALIGN_END_ADDR(struct qTD, qtd, 3));
+	flush_dcache_range((uint32_t)qtd,
+			   ALIGN_END_ADDR(struct qTD, qtd, qtd_count));
 
 	/* Set async. queue head pointer. */
 	ehci_writel(&hcor->or_asynclistaddr, (uint32_t)qh_list);
@@ -377,7 +409,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 		invalidate_dcache_range((uint32_t)qh,
 			ALIGN_END_ADDR(struct QH, qh, 1));
 		invalidate_dcache_range((uint32_t)qtd,
-			ALIGN_END_ADDR(struct qTD, qtd, 3));
+			ALIGN_END_ADDR(struct qTD, qtd, qtd_count));
 
 		token = hc32_to_cpu(vtd->qt_token);
 		if (!(token & 0x80))
@@ -450,9 +482,11 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
 		      ehci_readl(&hcor->or_portsc[1]));
 	}
 
+	free(qtd);
 	return (dev->status != USB_ST_NOT_PROC) ? 0 : -1;
 
 fail:
+	free(qtd);
 	return -1;
 }