usb: dwc2: Implement SPLIT transaction support

In contrast to non-SPLIT transfers each transaction has to be submitted
as an individual chunk.
The transaction state machine proceeds from SSPLIT to CSPLIT if the ACK
flag is set. CSPLIT has to be repeated while NYET is set.

Signed-off-by: Stefan Brüns <stefan.bruens@rwth-aachen.de>

drivers/usb/host/dwc2.c

@@ -837,6 +837,8 @@ int chunk_msg(struct dwc2_priv *priv, struct usb_device *dev,
 	int eptype = dwc2_eptype[usb_pipetype(pipe)];
 	int done = 0;
 	int ret = 0;
+	int do_split = 0;
+	int complete_split = 0;
 	uint32_t xfer_len;
 	uint32_t num_packets;
 	int stop_transfer = 0;
@@ -859,8 +861,26 @@ int chunk_msg(struct dwc2_priv *priv, struct usb_device *dev,
 	dwc_otg_hc_init(regs, DWC2_HC_CHANNEL, dev, devnum, ep, in,
 			eptype, max);
 
+	/* Check if the target is a FS/LS device behind a HS hub */
+	if (dev->speed != USB_SPEED_HIGH) {
+		uint8_t hub_addr;
+		uint8_t hub_port;
+		uint32_t hprt0 = readl(&regs->hprt0);
+		if ((hprt0 & DWC2_HPRT0_PRTSPD_MASK) ==
+		     DWC2_HPRT0_PRTSPD_HIGH) {
+			usb_find_usb2_hub_address_port(dev, &hub_addr,
+						       &hub_port);
+			dwc_otg_hc_init_split(hc_regs, hub_addr, hub_port);
+
+			do_split = 1;
+			num_packets = 1;
+			max_xfer_len = max;
+		}
+	}
+
 	do {
 		int actual_len = 0;
+		uint32_t hcint;
 		xfer_len = len - done;
 
 		if (xfer_len > max_xfer_len)
@@ -870,10 +890,29 @@ int chunk_msg(struct dwc2_priv *priv, struct usb_device *dev,
 		else
 			num_packets = 1;
 
+		if (complete_split)
+			setbits_le32(&hc_regs->hcsplt, DWC2_HCSPLT_COMPSPLT);
+		else if (do_split)
+			clrbits_le32(&hc_regs->hcsplt, DWC2_HCSPLT_COMPSPLT);
+
 		ret = transfer_chunk(hc_regs, priv->aligned_buffer, pid,
 				     in, (char *)buffer + done, num_packets,
 				     xfer_len, &actual_len);
 
+		hcint = readl(&hc_regs->hcint);
+		if (complete_split) {
+			stop_transfer = 0;
+			if (hcint & DWC2_HCINT_NYET)
+				ret = 0;
+			else
+				complete_split = 0;
+		} else if (do_split) {
+			if (hcint & DWC2_HCINT_ACK) {
+				ret = 0;
+				complete_split = 1;
+			}
+		}
+
 		if (ret)
 			break;
 
@@ -882,7 +921,11 @@ int chunk_msg(struct dwc2_priv *priv, struct usb_device *dev,
 
 		done += actual_len;
 
-	} while ((done < len) && !stop_transfer);
+	/* Transactions are done when when either all data is transferred or
+	 * there is a short transfer. In case of a SPLIT make sure the CSPLIT
+	 * is executed.
+	 */
+	} while (((done < len) && !stop_transfer) || complete_split);
 
 	writel(0, &hc_regs->hcintmsk);
 	writel(0xFFFFFFFF, &hc_regs->hcint);
@@ -925,31 +968,39 @@ static int _submit_control_msg(struct dwc2_priv *priv, struct usb_device *dev,
 					     setup);
 	}
 
+	/* SETUP stage */
 	pid = DWC2_HC_PID_SETUP;
-	ret = chunk_msg(priv, dev, pipe, &pid, 0, setup, 8);
+	do {
+		ret = chunk_msg(priv, dev, pipe, &pid, 0, setup, 8);
+	} while (ret == -EAGAIN);
 	if (ret)
 		return ret;
 
+	/* DATA stage */
+	act_len = 0;
 	if (buffer) {
 		pid = DWC2_HC_PID_DATA1;
-		ret = chunk_msg(priv, dev, pipe, &pid, usb_pipein(pipe), buffer,
-				len);
+		do {
+			ret = chunk_msg(priv, dev, pipe, &pid, usb_pipein(pipe),
+					buffer, len);
+			act_len += dev->act_len;
+			buffer += dev->act_len;
+			len -= dev->act_len;
+		} while (ret == -EAGAIN);
 		if (ret)
 			return ret;
-		act_len = dev->act_len;
-	} /* End of DATA stage */
-	else
-		act_len = 0;
-
-	/* STATUS stage */
-	if ((len == 0) || usb_pipeout(pipe))
+		status_direction = usb_pipeout(pipe);
+	} else {
+		/* No-data CONTROL always ends with an IN transaction */
 		status_direction = 1;
-	else
-		status_direction = 0;
+	}
 
+	/* STATUS stage */
 	pid = DWC2_HC_PID_DATA1;
-	ret = chunk_msg(priv, dev, pipe, &pid, status_direction,
-			priv->status_buffer, 0);
+	do {
+		ret = chunk_msg(priv, dev, pipe, &pid, status_direction,
+				priv->status_buffer, 0);
+	} while (ret == -EAGAIN);
 	if (ret)
 		return ret;