usb: xhci-mtk: fix in-ep's start-split check failure

It's wrong to use the data length in a CS (in uframe x) to check whether
there is a SS (in uframe x-2), because for a isoc-in ep, it may need some
CS to receive data;
Save the count of SS in a uframe for isoc/intr in-eps to fix the issue.

Fixes: 5c954e0 ("usb: xhci-mtk: improve split scheduling by separate IN/OUT budget")
Signed-off-by: Chunfeng Yun <chunfeng.yun@mediatek.com>
Link: https://lore.kernel.org/r/20231118033011.22033-1-chunfeng.yun@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

Author: Chunfeng Yun

drivers/usb/host/xhci-mtk-sch.c

@@ -650,9 +650,8 @@ static int check_isoc_ss_overlap(struct mu3h_sch_ep_info *sch_ep, u32 offset)
 
 		if (sch_ep->ep_type == ISOC_OUT_EP) {
 			for (j = 0; j < sch_ep->num_budget_microframes; j++) {
-				k = XHCI_MTK_BW_INDEX(base + j + CS_OFFSET);
-				/* use cs to indicate existence of in-ss @(base+j) */
-				if (tt->fs_bus_bw_in[k])
+				k = XHCI_MTK_BW_INDEX(base + j);
+				if (tt->in_ss_cnt[k])
 					return -ESCH_SS_OVERLAP;
 			}
 		} else if (sch_ep->ep_type == ISOC_IN_EP || sch_ep->ep_type == INT_IN_EP) {
@@ -769,6 +768,14 @@ static void update_sch_tt(struct mu3h_sch_ep_info *sch_ep, bool used)
 				tt->fs_frame_bw[f] -= (u16)sch_ep->bw_budget_table[j];
 			}
 		}
+
+		if (sch_ep->ep_type == ISOC_IN_EP || sch_ep->ep_type == INT_IN_EP) {
+			k = XHCI_MTK_BW_INDEX(base);
+			if (used)
+				tt->in_ss_cnt[k]++;
+			else
+				tt->in_ss_cnt[k]--;
+		}
 	}
 
 	if (used)

drivers/usb/host/xhci-mtk.h

@@ -38,13 +38,15 @@
  * @fs_bus_bw_in: save bandwidth used by FS/LS IN eps in each uframes
  * @ls_bus_bw: save bandwidth used by LS eps in each uframes
  * @fs_frame_bw: save bandwidth used by FS/LS eps in each FS frames
+ * @in_ss_cnt: the count of Start-Split for IN eps
  * @ep_list: Endpoints using this TT
  */
 struct mu3h_sch_tt {
 	u16 fs_bus_bw_out[XHCI_MTK_MAX_ESIT];
 	u16 fs_bus_bw_in[XHCI_MTK_MAX_ESIT];
 	u8 ls_bus_bw[XHCI_MTK_MAX_ESIT];
 	u16 fs_frame_bw[XHCI_MTK_FRAMES_CNT];
+	u8 in_ss_cnt[XHCI_MTK_MAX_ESIT];
 	struct list_head ep_list;
 };