libpayload: Add zero length packet support to UDC framework

Some IN transfers must be terminated by an empty packet
because otherwise the host wouldn't know.

The zlp() function determines this requirement in
accordance to USB rules: If the transfer's size is aligned
to the maximum packet size, and the host expects a larger
transfer, add the empty packet as a hint.

BRANCH=none
BUG=none
TEST=USB device mode still works

Change-Id: Ia69f3d017f72a3a0e0b21bac72fe97be184c7daa
Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Commit-Id: fd0e946e4948a74a9ed15a5eed6ce827b7672a56
Original-Change-Id: I8153cc5bd2ff1c88e383c1dbcddaf1bf72f9194c
Original-Signed-off-by: Patrick Georgi <pgeorgi@chromium.org>
Original-Reviewed-on: https://chromium-review.googlesource.com/250790
Original-Reviewed-by: Furquan Shaikh <furquan@chromium.org>
Reviewed-on: http://review.coreboot.org/9784
Tested-by: build bot (Jenkins)
Reviewed-by: Stefan Reinauer <stefan.reinauer@coreboot.org>

2 files changed, 33 insertions, 4 deletions

diff --git a/payloads/libpayload/drivers/udc/chipidea.c b/payloads/libpayload/drivers/udc/chipidea.c
index e06f0d282449..58bea063e793 100644
--- a/payloads/libpayload/drivers/udc/chipidea.c
+++ b/payloads/libpayload/drivers/udc/chipidea.c
@@ -153,6 +153,7 @@ static void chipidea_start_ep(struct usbdev_ctrl *this,
 	setbits_le32(&p->opreg->epctrl[ep],
 		((1 << 7) | (1 << 6) | (ep_type << 2)) << (in_dir*16));
 	p->ep_busy[ep][in_dir] = 0;
+	this->ep_mps[ep][in_dir] = mps;
 }
 
 static void advance_endpoint(struct chipidea_pdata *p, int endpoint, int in_dir)
@@ -463,6 +464,14 @@ struct usbdev_ctrl *chipidea_init(device_descriptor_t *dd)
 	ctrl->free_data = chipidea_free;
 	ctrl->initialized = 0;
 
+	int i;
+	ctrl->ep_mps[0][0] = 64;
+	ctrl->ep_mps[0][1] = 64;
+	for (i = 1; i < 16; i++) {
+		ctrl->ep_mps[i][0] = 512;
+		ctrl->ep_mps[i][1] = 512;
+	}
+
 	if (!chipidea_hw_init(ctrl, (void *)0x7d000000, dd)) {
 		free(ctrl->pdata);
 		free(ctrl);
diff --git a/payloads/libpayload/drivers/udc/udc.c b/payloads/libpayload/drivers/udc/udc.c
index cdc2b29f95cd..89a7d1dac255 100644
--- a/payloads/libpayload/drivers/udc/udc.c
+++ b/payloads/libpayload/drivers/udc/udc.c
@@ -47,8 +47,26 @@
 
 #define min(a, b) (((a) < (b)) ? (a) : (b))
 
-// TODO: make this right
-#define ZLP(len, explen) 0
+/* determine if an additional zero length packet is necessary for
+ * a transfer */
+static unsigned int zlp(struct usbdev_ctrl *this, const int epnum,
+	const int len, const int explen)
+{
+	const unsigned int mps = this->ep_mps[epnum][1];
+
+	/* zero length transfers are handled explicitly */
+	if (len == 0)
+		return 0;
+	/* host expects exactly the right amount, so no zlp necessary */
+	if (len == explen)
+		return 0;
+	/* last packet will be short -> host knows that transfer is over */
+	if ((len % mps) != 0)
+		return 0;
+
+	/* otherwise we need an extra zero length packet */
+	return 1;
+}
 
 static struct usbdev_configuration *fetch_config(struct usbdev_ctrl *this,
 	int id)
@@ -90,6 +108,8 @@ static void enable_interface(struct usbdev_ctrl *this, int iface_num)
 		this->start_ep(this, ep, in_dir, ep_type, mps);
 	}
 
+	this->current_iface = iface;
+
 	// gadget specific configuration
 	if (iface->init)
 		iface->init(this);
@@ -268,7 +288,7 @@ static int setup_ep0(struct usbdev_ctrl *this, dev_req_t *dr)
 		/* data phase IN */
 		this->enqueue_packet(this, 0, 1, data,
 			min(size, dr->wLength),
-			ZLP(size, dr->wLength), 1);
+			zlp(this, 0, size, dr->wLength), 1);
 
 		/* status phase OUT */
 		this->enqueue_packet(this, 0, 0, NULL, 0, 0, 0);
@@ -284,7 +304,7 @@ static int setup_ep0(struct usbdev_ctrl *this, dev_req_t *dr)
 		/* data phase IN */
 		this->enqueue_packet(this, 0, 1, (void *)dd,
 			min(sizeof(*dd), dr->wLength),
-			ZLP(sizeof(*dd), dr->wLength), 1);
+			zlp(this, 0, sizeof(*dd), dr->wLength), 1);
 
 		/* status phase OUT */
 		this->enqueue_packet(this, 0, 0, NULL, 0, 0, 0);