usb: dwc2: host: program descriptor for next frame

Isochronous descriptor is currently programmed for the frame
after the last descriptor was programmed.

If the last descriptor frame underrun, then current descriptor must
take this into account and must be programmed on the current frame + 1.
This overrun usually happens when system is loaded and dwc2 can't init
descriptor list in time.

Acked-by: John Youn <johnyoun@synopsys.com>
Signed-off-by: Gregory Herrero <gregory.herrero@intel.com>
Signed-off-by: Felipe Balbi <balbi@ti.com>

drivers/usb/dwc2/hcd.h

@@ -340,6 +340,8 @@ struct dwc2_qtd {
 	u8 isoc_split_pos;
 	u16 isoc_frame_index;
 	u16 isoc_split_offset;
+	u16 isoc_td_last;
+	u16 isoc_td_first;
 	u32 ssplit_out_xfer_count;
 	u8 error_count;
 	u8 n_desc;

drivers/usb/dwc2/hcd_ddma.c

@@ -547,11 +547,32 @@ static void dwc2_init_isoc_dma_desc(struct dwc2_hsotg *hsotg,
 {
 	struct dwc2_qtd *qtd;
 	u32 max_xfer_size;
-	u16 idx, inc, n_desc, ntd_max = 0;
+	u16 idx, inc, n_desc = 0, ntd_max = 0;
+	u16 cur_idx;
+	u16 next_idx;
 
 	idx = qh->td_last;
 	inc = qh->interval;
-	n_desc = 0;
+	hsotg->frame_number = dwc2_hcd_get_frame_number(hsotg);
+	cur_idx = dwc2_frame_list_idx(hsotg->frame_number);
+	next_idx = dwc2_desclist_idx_inc(qh->td_last, inc, qh->dev_speed);
+
+	/*
+	 * Ensure current frame number didn't overstep last scheduled
+	 * descriptor. If it happens, the only way to recover is to move
+	 * qh->td_last to current frame number + 1.
+	 * So that next isoc descriptor will be scheduled on frame number + 1
+	 * and not on a past frame.
+	 */
+	if (dwc2_frame_idx_num_gt(cur_idx, next_idx) || (cur_idx == next_idx)) {
+		if (inc < 32) {
+			dev_vdbg(hsotg->dev,
+				 "current frame number overstep last descriptor\n");
+			qh->td_last = dwc2_desclist_idx_inc(cur_idx, inc,
+							    qh->dev_speed);
+			idx = qh->td_last;
+		}
+	}
 
 	if (qh->interval) {
 		ntd_max = (dwc2_max_desc_num(qh) + qh->interval - 1) /
@@ -564,13 +585,20 @@ static void dwc2_init_isoc_dma_desc(struct dwc2_hsotg *hsotg,
 			MAX_ISOC_XFER_SIZE_HS : MAX_ISOC_XFER_SIZE_FS;
 
 	list_for_each_entry(qtd, &qh->qtd_list, qtd_list_entry) {
+		if (qtd->in_process &&
+		    qtd->isoc_frame_index_last ==
+		    qtd->urb->packet_count)
+			continue;
+
+		qtd->isoc_td_first = idx;
 		while (qh->ntd < ntd_max && qtd->isoc_frame_index_last <
 						qtd->urb->packet_count) {
 			dwc2_fill_host_isoc_dma_desc(hsotg, qtd, qh,
 						     max_xfer_size, idx);
 			idx = dwc2_desclist_idx_inc(idx, inc, qh->dev_speed);
 			n_desc++;
 		}
+		qtd->isoc_td_last = idx;
 		qtd->in_process = 1;
 	}