usb: dwc2: host: fix split transfer schedule sequence

We're supposed to keep outstanding splits in order.  Keep track of a
list of the order of splits and process channel interrupts in that
order.

Without this change and the following setup:
* Rockchip rk3288 Chromebook, using port ff540000
  -> Pluggable 7-port Hub with Charging (powered)
     -> Microsoft Wireless Keyboard 2000 in port 1.
     -> Das Keyboard in port 2.

...I find that I get dropped keys on the Microsoft keyboard (I'm sure
there are other combinations that fail, but this documents my test).
Specifically I've been typing "hahahahahahaha" on the keyboard and often
see keys dropped or repeated.

After this change the above setup works properly.  This patch is based
on a previous patch proposed by Yunzhi Li ("usb: dwc2: hcd: fix periodic
transfer schedule sequence")

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Douglas Anderson <dianders@chromium.org>
Signed-off-by: Yunzhi Li <lyz@rock-chips.com>
Reviewed-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Heiko Stuebner <heiko@sntech.de>
Tested-by: Kever Yang <kever.yang@rock-chips.com>
Tested-by: Stefan Wahren <stefan.wahren@i2se.com>
Signed-off-by: Felipe Balbi <balbi@kernel.org>

drivers/usb/dwc2/core.c

@@ -1676,6 +1676,8 @@ void dwc2_hc_cleanup(struct dwc2_hsotg *hsotg, struct dwc2_host_chan *chan)
 
 	chan->xfer_started = 0;
 
+	list_del_init(&chan->split_order_list_entry);
+
 	/*
 	 * Clear channel interrupt enables and any unhandled channel interrupt
 	 * conditions

drivers/usb/dwc2/core.h

@@ -657,6 +657,7 @@ struct dwc2_hregs_backup {
  *                      periodic_sched_ready because it must be rescheduled for
  *                      the next frame. Otherwise, the item moves to
  *                      periodic_sched_inactive.
+ * @split_order:        List keeping track of channels doing splits, in order.
  * @periodic_usecs:     Total bandwidth claimed so far for periodic transfers.
  *                      This value is in microseconds per (micro)frame. The
  *                      assumption is that all periodic transfers may occur in
@@ -780,6 +781,7 @@ struct dwc2_hsotg {
 	struct list_head periodic_sched_ready;
 	struct list_head periodic_sched_assigned;
 	struct list_head periodic_sched_queued;
+	struct list_head split_order;
 	u16 periodic_usecs;
 	u16 frame_usecs[8];
 	u16 frame_number;

drivers/usb/dwc2/hcd.c

@@ -1045,6 +1045,11 @@ static int dwc2_queue_transaction(struct dwc2_hsotg *hsotg,
 {
 	int retval = 0;
 
+	if (chan->do_split)
+		/* Put ourselves on the list to keep order straight */
+		list_move_tail(&chan->split_order_list_entry,
+			       &hsotg->split_order);
+
 	if (hsotg->core_params->dma_enable > 0) {
 		if (hsotg->core_params->dma_desc_enable > 0) {
 			if (!chan->xfer_started ||
@@ -3153,6 +3158,8 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq)
 	INIT_LIST_HEAD(&hsotg->periodic_sched_assigned);
 	INIT_LIST_HEAD(&hsotg->periodic_sched_queued);
 
+	INIT_LIST_HEAD(&hsotg->split_order);
+
 	/*
 	 * Create a host channel descriptor for each host channel implemented
 	 * in the controller. Initialize the channel descriptor array.
@@ -3166,6 +3173,7 @@ int dwc2_hcd_init(struct dwc2_hsotg *hsotg, int irq)
 		if (channel == NULL)
 			goto error3;
 		channel->hc_num = i;
+		INIT_LIST_HEAD(&channel->split_order_list_entry);
 		hsotg->hc_ptr_array[i] = channel;
 	}
 

drivers/usb/dwc2/hcd.h

@@ -106,6 +106,7 @@ struct dwc2_qh;
  * @hc_list_entry:      For linking to list of host channels
  * @desc_list_addr:     Current QH's descriptor list DMA address
  * @desc_list_sz:       Current QH's descriptor list size
+ * @split_order_list_entry: List entry for keeping track of the order of splits
  *
  * This structure represents the state of a single host channel when acting in
  * host mode. It contains the data items needed to transfer packets to an
@@ -158,6 +159,7 @@ struct dwc2_host_chan {
 	struct list_head hc_list_entry;
 	dma_addr_t desc_list_addr;
 	u32 desc_list_sz;
+	struct list_head split_order_list_entry;
 };
 
 struct dwc2_hcd_pipe_info {

drivers/usb/dwc2/hcd_intr.c

@@ -2075,6 +2075,7 @@ static void dwc2_hc_intr(struct dwc2_hsotg *hsotg)
 {
 	u32 haint;
 	int i;
+	struct dwc2_host_chan *chan, *chan_tmp;
 
 	haint = dwc2_readl(hsotg->regs + HAINT);
 	if (dbg_perio()) {
@@ -2083,6 +2084,22 @@ static void dwc2_hc_intr(struct dwc2_hsotg *hsotg)
 		dev_vdbg(hsotg->dev, "HAINT=%08x\n", haint);
 	}
 
+	/*
+	 * According to USB 2.0 spec section 11.18.8, a host must
+	 * issue complete-split transactions in a microframe for a
+	 * set of full-/low-speed endpoints in the same relative
+	 * order as the start-splits were issued in a microframe for.
+	 */
+	list_for_each_entry_safe(chan, chan_tmp, &hsotg->split_order,
+				 split_order_list_entry) {
+		int hc_num = chan->hc_num;
+
+		if (haint & (1 << hc_num)) {
+			dwc2_hc_n_intr(hsotg, hc_num);
+			haint &= ~(1 << hc_num);
+		}
+	}
+
 	for (i = 0; i < hsotg->core_params->host_channels; i++) {
 		if (haint & (1 << i))
 			dwc2_hc_n_intr(hsotg, i);