[U-Boot] [PATCH v3 8/8] ehci: Optimize qTD allocations
Benoît Thébaudeau
benoit.thebaudeau at advansee.com
Thu Aug 9 23:54:15 CEST 2012
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: 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: N/A.
Changes for v3:
- New patch.
.../drivers/usb/host/ehci-hcd.c | 68 +++++++++++---------
1 file changed, 38 insertions(+), 30 deletions(-)
diff --git u-boot-usb-8d5fb14.orig/drivers/usb/host/ehci-hcd.c u-boot-usb-8d5fb14/drivers/usb/host/ehci-hcd.c
index 84c7d08..37517cb 100644
--- u-boot-usb-8d5fb14.orig/drivers/usb/host/ehci-hcd.c
+++ u-boot-usb-8d5fb14/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));
@@ -314,9 +313,10 @@ 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) == 0);
+ maxpacket = usb_maxpacket(dev, pipe);
endpt = (8 << QH_ENDPT1_RL) |
(c << QH_ENDPT1_C) |
- (usb_maxpacket(dev, pipe) << QH_ENDPT1_MAXPKTLEN) |
+ (maxpacket << QH_ENDPT1_MAXPKTLEN) |
(0 << QH_ENDPT1_H) |
(QH_ENDPT1_DTC_DT_FROM_QTD << QH_ENDPT1_DTC) |
(usb_pipespeed(pipe) << QH_ENDPT1_EPS) |
@@ -362,6 +362,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
}
if (length > 0 || req == NULL) {
+ uint32_t qtd_toggle = toggle;
uint8_t *buf_ptr = buffer;
int left_length = length;
@@ -379,9 +380,9 @@ 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.
@@ -401,7 +402,7 @@ ehci_submit_async(struct usb_device *dev, unsigned long pipe, void *buffer,
cpu_to_hc32(QT_NEXT_TERMINATE);
qtd[qtd_counter].qt_altnext =
cpu_to_hc32(QT_NEXT_TERMINATE);
- token = (toggle << QT_TOKEN_DT) |
+ token = (qtd_toggle << QT_TOKEN_DT) |
(xfr_bytes << QT_TOKEN_TOTALBYTES) |
((req == NULL) << QT_TOKEN_IOC) |
(0 << QT_TOKEN_CPAGE) |
@@ -418,6 +419,13 @@ 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)
+ qtd_toggle ^= 1;
buf_ptr += xfr_bytes;
left_length -= xfr_bytes;
} while (left_length > 0);
@@ -944,11 +952,11 @@ 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 "
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