[U-Boot] [PATCH v4 7/7] ehci: Optimize qTD allocations

Benoît Thébaudeau
2012-08-10T16:27:23Z

Relax the qTD transfer alignment constraints in order to need less qTDs for
buffers that are aligned to 512 bytes but not to pages.

Signed-off-by: Beno?t Th?baudeau <benoit.thebaudeau@advansee.com>
Cc: Marek Vasut <marex@denx.de>
Cc: Ilya Yanok <ilya.yanok@cogentembedded.com>
Cc: Stefan Herbrechtsmeier <stefan@herbrechtsmeier.net>
---
Changes for v2: N/A.
Changes for v3:
- New patch.
Changes for v4:
- Optimize away the qtd_toggle variable.

.../drivers/usb/host/ehci-hcd.c | 67 +++++++++++---------
1 file changed, 37 insertions(+), 30 deletions(-)

diff --git u-boot-usb-4f8254e.orig/drivers/usb/host/ehci-hcd.c u-boot-usb-4f8254e/drivers/usb/host/ehci-hcd.c
index a0ef5db..18b4bc6 100644
--- u-boot-usb-4f8254e.orig/drivers/usb/host/ehci-hcd.c
+++ u-boot-usb-4f8254e/drivers/usb/host/ehci-hcd.c
@@ -215,7 +215,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
volatile struct qTD *vtd;
unsigned long ts;
uint32_t *tdp;
- uint32_t endpt, token, usbsts;
+ uint32_t endpt, maxpacket, token, usbsts;
uint32_t c, toggle;
uint32_t cmd;
int timeout;
@@ -230,6 +230,7 @@ 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));

+#define PKT_ALIGN 512
/*
* The USB transfer is split into qTD transfers. Eeach qTD transfer is
* described by a transfer descriptor (the qTD). The qTDs form a linked
@@ -251,43 +252,41 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
if (length > 0 || req == NULL) {
/*
* Determine the qTD transfer size that will be used for the
- * data payload (not considering the final qTD transfer, which
- * may be shorter).
+ * data payload (not considering the first qTD transfer, which
+ * may be longer or shorter, and the final one, which may be
+ * shorter).
*
* In order to keep each packet within a qTD transfer, the qTD
- * transfer size is aligned to EHCI_PAGE_SIZE, which is a
- * multiple of wMaxPacketSize (except in some cases for
- * interrupt transfers, see comment in submit_int_msg()).
+ * transfer size is aligned to PKT_ALIGN, which is a multiple of
+ * wMaxPacketSize (except in some cases for interrupt transfers,
+ * see comment in submit_int_msg()).
*
- * By default, i.e. if the input buffer is page-aligned,
+ * By default, i.e. if the input buffer is aligned to PKT_ALIGN,
* QT_BUFFER_CNT full pages will be used.
*/
int xfr_sz = QT_BUFFER_CNT;
/*
- * However, if the input buffer is not page-aligned, the qTD
- * transfer size will be one page shorter, and the first qTD
+ * However, if the input buffer is not aligned to PKT_ALIGN, the
+ * qTD transfer size will be one page shorter, and the first qTD
* data buffer of each transfer will be page-unaligned.
*/
- if ((uint32_t)buffer & (EHCI_PAGE_SIZE - 1))
+ if ((uint32_t)buffer & (PKT_ALIGN - 1))
xfr_sz--;
/* Convert the qTD transfer size to bytes. */
xfr_sz *= EHCI_PAGE_SIZE;
/*
- * Determine the number of qTDs that will be required for the
- * data payload. This value has to be rounded up since the final
- * qTD transfer may be shorter than the regular qTD transfer
- * size that has just been computed.
+ * Approximate by excess the number of qTDs that will be
+ * required for the data payload. The exact formula is way more
+ * complicated and saves at most 2 qTDs, i.e. a total of 128
+ * bytes.
*/
- qtd_count += DIV_ROUND_UP(length, xfr_sz);
- /* ZLPs also need a qTD. */
- if (!qtd_count)
- qtd_count++;
+ qtd_count += 2 + length / xfr_sz;
}
/*
- * Threshold value based on the worst-case total size of the qTDs to allocate
- * for a mass-storage transfer of 65535 blocks of 512 bytes.
+ * Threshold value based on the worst-case total size of the allocated qTDs for
+ * a mass-storage transfer of 65535 blocks of 512 bytes.
*/
-#if CONFIG_SYS_MALLOC_LEN <= 128 * 1024
+#if CONFIG_SYS_MALLOC_LEN <= 64 + 128 * 1024
#warning CONFIG_SYS_MALLOC_LEN may be too small for EHCI
#endif
qtd = memalign(USB_DMA_MINALIGN, qtd_count * sizeof(struct qTD));
@@ -313,8 +312,9 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
*/
qh->qh_link = cpu_to_hc32((uint32_t)qh_list | QH_LINK_TYPE_QH);
c = usb_pipespeed(pipe) != USB_SPEED_HIGH && !usb_pipeendpoint(pipe);
+ maxpacket = usb_maxpacket(dev, pipe);
endpt = QH_ENDPT1_RL(8) | QH_ENDPT1_C(c) |
- QH_ENDPT1_MAXPKTLEN(usb_maxpacket(dev, pipe)) | QH_ENDPT1_H(0) |
+ QH_ENDPT1_MAXPKTLEN(maxpacket) | QH_ENDPT1_H(0) |
QH_ENDPT1_DTC(QH_ENDPT1_DTC_DT_FROM_QTD) |
QH_ENDPT1_EPS(usb_pipespeed(pipe)) |
QH_ENDPT1_ENDPT(usb_pipeendpoint(pipe)) | QH_ENDPT1_I(0) |
@@ -373,9 +373,9 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
xfr_bytes -= (uint32_t)buf_ptr & (EHCI_PAGE_SIZE - 1);
/*
* In order to keep each packet within a qTD transfer,
- * align the qTD transfer size to EHCI_PAGE_SIZE.
+ * align the qTD transfer size to PKT_ALIGN.
*/
- xfr_bytes &= ~(EHCI_PAGE_SIZE - 1);
+ xfr_bytes &= ~(PKT_ALIGN - 1);
/*
* This transfer may be shorter than the available qTD
* transfer size that has just been computed.
@@ -411,6 +411,13 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
/* Update previous qTD! */
*tdp = cpu_to_hc32((uint32_t)&qtd[qtd_counter]);
tdp = &qtd[qtd_counter++].qt_next;
+ /*
+ * Data toggle has to be adjusted since the qTD transfer
+ * size is not always an even multiple of
+ * wMaxPacketSize.
+ */
+ if ((xfr_bytes / maxpacket) & 1)
+ toggle ^= 1;
buf_ptr += xfr_bytes;
left_length -= xfr_bytes;
} while (left_length > 0);
@@ -426,7 +433,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
*/
qtd[qtd_counter].qt_next = cpu_to_hc32(QT_NEXT_TERMINATE);
qtd[qtd_counter].qt_altnext = cpu_to_hc32(QT_NEXT_TERMINATE);
- token = QT_TOKEN_DT(toggle) | QT_TOKEN_TOTALBYTES(0) |
+ token = QT_TOKEN_DT(1) | QT_TOKEN_TOTALBYTES(0) |
QT_TOKEN_IOC(1) | QT_TOKEN_CPAGE(0) | QT_TOKEN_CERR(3) |
QT_TOKEN_PID(usb_pipein(pipe) ?
QT_TOKEN_PID_OUT : QT_TOKEN_PID_IN) |
@@ -931,11 +938,11 @@ submit_int_msg(struct usb_device *dev, unsigned long pipe, void *buffer,
* because bInterval is ignored.
*
* Also, ehci_submit_async() relies on wMaxPacketSize being a power of 2
- * if several qTDs are required, while the USB specification does not
- * constrain this for interrupt transfers. That means that
- * ehci_submit_async() would support interrupt transfers requiring
- * several transactions only as long as the transfer size does not
- * require more than a single qTD.
+ * <= PKT_ALIGN if several qTDs are required, while the USB
+ * specification does not constrain this for interrupt transfers. That
+ * means that ehci_submit_async() would support interrupt transfers
+ * requiring several transactions only as long as the transfer size does
+ * not require more than a single qTD.
*/
if (length > usb_maxpacket(dev, pipe)) {
printf("%s: Interrupt transfers requiring several transactions "