USB: Add memcpy_from_usbram and update existing memcpy

Previously there was just a memcpy_usbram that copied to
USB packet memory, and no routine to copy out.  This adds
the "from" version and renames and improves to "to" version.

The improvement is that the new "to" version correctly
handles unaligned beginning and endings of the region to
be copied.  These need to be read/modify/write accesses since
the USB packet ram has to be manipulated in 16-bit chunks.

Signed-off-by: Anton Staaf <robotboy@chromium.org>

BRANCH=None
BUG=None
TEST=make buildall -j
     Verify that discovery-stm32f072 still enumerates and communicates
     correctly over USB.

Change-Id: I94353e66ad0248d4e674abb29f9a88e979767655
Reviewed-on: https://chromium-review.googlesource.com/238764
Tested-by: Anton Staaf <robotboy@chromium.org>
Reviewed-by: Vic Yang <victoryang@chromium.org>
Commit-Queue: Anton Staaf <robotboy@chromium.org>
Trybot-Ready: Anton Staaf <robotboy@chromium.org>

2 files changed, 59 insertions, 5 deletions

diff --git a/chip/stm32/usb.c b/chip/stm32/usb.c
index 82c1337a40..af9082299e 100644
--- a/chip/stm32/usb.c
+++ b/chip/stm32/usb.c
@@ -155,7 +155,7 @@ static void ep0_rx(void)
 			desc_ptr = desc + USB_MAX_PACKET_SIZE;
 			len = USB_MAX_PACKET_SIZE;
 		}
-		memcpy_usbram(ep0_buf_tx, desc, len);
+		memcpy_to_usbram(ep0_buf_tx, desc, len);
 		if (type == USB_DT_CONFIGURATION)
 			/* set the real descriptor size */
 			ep0_buf_tx[1] = USB_DESC_SIZE;
@@ -166,7 +166,7 @@ static void ep0_rx(void)
 	} else if (req == (USB_DIR_IN | (USB_REQ_GET_STATUS << 8))) {
 		uint16_t zero = 0;
 		/* Get status */
-		memcpy_usbram(ep0_buf_tx, (void *)&zero, 2);
+		memcpy_to_usbram(ep0_buf_tx, (void *)&zero, 2);
 		btable_ep[0].tx_count = 2;
 		STM32_TOGGLE_EP(0, EP_TX_RX_MASK, EP_TX_RX_VALID,
 			  EP_STATUS_OUT /*null OUT transaction */);
@@ -208,7 +208,7 @@ static void ep0_tx(void)
 	if (desc_ptr) {
 		/* we have an on-going descriptor transfer */
 		int len = MIN(desc_left, USB_MAX_PACKET_SIZE);
-		memcpy_usbram(ep0_buf_tx, desc_ptr, len);
+		memcpy_to_usbram(ep0_buf_tx, desc_ptr, len);
 		btable_ep[0].tx_count = len;
 		desc_left -= len;
 		desc_ptr += len;
@@ -341,3 +341,57 @@ int usb_is_enabled(void)
 {
 	return (STM32_RCC_APB1ENR & STM32_RCC_PB1_USB) ? 1 : 0;
 }
+
+void *memcpy_to_usbram(void *dest, const void *src, size_t n)
+{
+	int       i;
+	uint8_t  *s = (uint8_t *) src;
+	usb_uint *d = (usb_uint *)((uintptr_t) dest & ~1);
+
+	if ((((uintptr_t) dest) & 1) && n) {
+		/*
+		 * The first destination byte is not aligned, perform a read/
+		 * modify/write.
+		 */
+		*d = (*d & ~0xff00) | (*s << 8);
+		n--;
+		s++;
+		d++;
+	}
+
+	for (i = 0; i < n / 2; i++, s += 2)
+		*d++ = (s[1] << 8) | s[0];
+
+	/*
+	 * There is a trailing byte to write into a final USB packet memory
+	 * location, use a read/modify/write to be safe.
+	 */
+	if (n & 1)
+		*d = (*d & ~0x00ff) | *s;
+
+	return dest;
+}
+
+void *memcpy_from_usbram(void *dest, const void *src, size_t n)
+{
+	int       i;
+	usb_uint *s = (usb_uint *)((uintptr_t) src & ~1);
+	uint8_t  *d = (uint8_t *) dest;
+
+	if ((((uintptr_t) src) & 1) && n) {
+		*d++ = *s++ >> 8;
+		n--;
+	}
+
+	for (i = 0; i < n / 2; i++) {
+		usb_uint value = *s++;
+
+		*d++ = (value >> 0) & 0xff;
+		*d++ = (value >> 8) & 0xff;
+	}
+
+	if (n & 1)
+		*d = *s;
+
+	return dest;
+}
diff --git a/chip/stm32/usb_hid.c b/chip/stm32/usb_hid.c
index bdcf09c3f8..8b39778202 100644
--- a/chip/stm32/usb_hid.c
+++ b/chip/stm32/usb_hid.c
@@ -88,7 +88,7 @@ static usb_uint hid_ep_buf[HID_REPORT_SIZE / 2] __usb_ram;
 
 void set_keyboard_report(uint64_t rpt)
 {
-	memcpy_usbram(hid_ep_buf, (const uint8_t *)&rpt, sizeof(rpt));
+	memcpy_to_usbram(hid_ep_buf, &rpt, sizeof(rpt));
 	/* enable TX */
 	STM32_TOGGLE_EP(USB_EP_HID, EP_TX_MASK, EP_TX_VALID, 0);
 }
@@ -124,7 +124,7 @@ static int hid_iface_request(usb_uint *ep0_buf_rx, usb_uint *ep0_buf_tx)
 			      (USB_REQ_GET_DESCRIPTOR << 8))) &&
 			      (ep0_buf_rx[1] == (USB_HID_DT_REPORT << 8))) {
 		/* Setup : HID specific : Get Report descriptor */
-		memcpy_usbram(ep0_buf_tx, report_desc,
+		memcpy_to_usbram(ep0_buf_tx, report_desc,
 				 sizeof(report_desc));
 		btable_ep[0].tx_count = MIN(ep0_buf_rx[3],
 				   sizeof(report_desc));