[RFC PATCH] usb: xhci-mtk: handle bandwidth table rollover

[Ikjoon Jang <ikjn@chromium.org>]

xhci-mtk has 64 slots for periodic bandwidth calculations and each
slot represents byte budgets on a microframe. When an endpoint's
allocation sits on the boundary of the table, byte budgets' slot
should be rolled over but the current implementation doesn't.

This patch applies a 6 bits mask to the microframe index to handle
its rollover 64 slots and prevent out-of-bounds array access.

Signed-off-by: Ikjoon Jang <ikjn@chromium.org>
---

 drivers/usb/host/xhci-mtk-sch.c | 79 +++++++++------------------------
 drivers/usb/host/xhci-mtk.h     |  1 +
 2 files changed, 23 insertions(+), 57 deletions(-)

diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-mtk-sch.c
index 46cbf5d54f4f..ef16cd124343 100644
--- a/drivers/usb/host/xhci-mtk-sch.c
+++ b/drivers/usb/host/xhci-mtk-sch.c
@@ -411,18 +411,13 @@ static void setup_sch_info(struct xhci_ep_ctx *ep_ctx,
 static u32 get_max_bw(struct mu3h_sch_bw_info *sch_bw,
 	struct mu3h_sch_ep_info *sch_ep, u32 offset)
 {
-	u32 num_esit;
-	u32 max_bw = 0;
-	u32 bw;
-	int i;
-	int j;
-
-	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;
-	for (i = 0; i < num_esit; i++) {
-		u32 base = offset + i * sch_ep->esit;
+	u32 bw, max_bw = 0;
+	int i, j, idx;
 
+	for (i = 0; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {
 		for (j = 0; j < sch_ep->num_budget_microframes; j++) {
-			bw = sch_bw->bus_bw[base + j] +
+			idx = XHCI_MTK_BW_IDX(i + offset + j);
+			bw = sch_bw->bus_bw[idx] +
 					sch_ep->bw_budget_table[j];
 			if (bw > max_bw)
 				max_bw = bw;
@@ -434,20 +429,16 @@ static u32 get_max_bw(struct mu3h_sch_bw_info *sch_bw,
 static void update_bus_bw(struct mu3h_sch_bw_info *sch_bw,
 	struct mu3h_sch_ep_info *sch_ep, bool used)
 {
-	u32 num_esit;
-	u32 base;
-	int i;
-	int j;
+	int i, j, idx;
 
-	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;
-	for (i = 0; i < num_esit; i++) {
-		base = sch_ep->offset + i * sch_ep->esit;
+	for (i = 0; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {
 		for (j = 0; j < sch_ep->num_budget_microframes; j++) {
+			idx = XHCI_MTK_BW_IDX(i + sch_ep->offset + j);
 			if (used)
-				sch_bw->bus_bw[base + j] +=
+				sch_bw->bus_bw[idx] +=
 					sch_ep->bw_budget_table[j];
 			else
-				sch_bw->bus_bw[base + j] -=
+				sch_bw->bus_bw[idx] -=
 					sch_ep->bw_budget_table[j];
 		}
 	}
@@ -456,22 +447,18 @@ static void update_bus_bw(struct mu3h_sch_bw_info *sch_bw,
 static int check_fs_bus_bw(struct mu3h_sch_ep_info *sch_ep, int offset)
 {
 	struct mu3h_sch_tt *tt = sch_ep->sch_tt;
-	u32 num_esit, tmp;
-	int base;
-	int i, j;
+	u32 bw;
+	int i, j, idx;
 	u8 uframes = DIV_ROUND_UP(sch_ep->maxpkt, FS_PAYLOAD_MAX);
 
-	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;
-
 	if (sch_ep->ep_type == INT_IN_EP || sch_ep->ep_type == ISOC_IN_EP)
 		offset++;
 
-	for (i = 0; i < num_esit; i++) {
-		base = offset + i * sch_ep->esit;
-
+	for (i = 0; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {
 		for (j = 0; j < uframes; j++) {
-			tmp = tt->fs_bus_bw[base + j] + sch_ep->bw_cost_per_microframe;
-			if (tmp > FS_PAYLOAD_MAX)
+			idx = XHCI_MTK_BW_IDX(i + offset + j);
+			bw = tt->fs_bus_bw[idx] + sch_ep->bw_cost_per_microframe;
+			if (bw > FS_PAYLOAD_MAX)
 				return -ESCH_BW_OVERFLOW;
 		}
 	}
@@ -544,14 +531,11 @@ static int check_sch_tt(struct mu3h_sch_ep_info *sch_ep, u32 offset)
 static void update_sch_tt(struct mu3h_sch_ep_info *sch_ep, bool used)
 {
 	struct mu3h_sch_tt *tt = sch_ep->sch_tt;
-	u32 base, num_esit;
 	int bw_updated;
-	int i, j;
+	int i, j, idx;
 	int offset = sch_ep->offset;
 	u8 uframes = DIV_ROUND_UP(sch_ep->maxpkt, FS_PAYLOAD_MAX);
 
-	num_esit = XHCI_MTK_MAX_ESIT / sch_ep->esit;
-
 	if (used)
 		bw_updated = sch_ep->bw_cost_per_microframe;
 	else
@@ -560,11 +544,11 @@ static void update_sch_tt(struct mu3h_sch_ep_info *sch_ep, bool used)
 	if (sch_ep->ep_type == INT_IN_EP || sch_ep->ep_type == ISOC_IN_EP)
 		offset++;
 
-	for (i = 0; i < num_esit; i++) {
-		base = offset + i * sch_ep->esit;
-
-		for (j = 0; j < uframes; j++)
-			tt->fs_bus_bw[base + j] += bw_updated;
+	for (i = 0; i < XHCI_MTK_MAX_ESIT; i += sch_ep->esit) {
+		for (j = 0; j < uframes; j++) {
+			idx = XHCI_MTK_BW_IDX(i + offset + j);
+			tt->fs_bus_bw[idx] += bw_updated;
+		}
 	}
 
 	if (used)
@@ -586,25 +570,9 @@ static int load_ep_bw(struct mu3h_sch_bw_info *sch_bw,
 	return 0;
 }
 
-static u32 get_esit_boundary(struct mu3h_sch_ep_info *sch_ep)
-{
-	u32 boundary = sch_ep->esit;
-
-	if (sch_ep->sch_tt) { /* LS/FS with TT */
-		/* tune for CS */
-		if (sch_ep->ep_type != ISOC_OUT_EP)
-			boundary++;
-		else if (boundary > 1) /* normally esit >= 8 for FS/LS */
-			boundary--;
-	}
-
-	return boundary;
-}
-
 static int check_sch_bw(struct mu3h_sch_ep_info *sch_ep)
 {
 	struct mu3h_sch_bw_info *sch_bw = sch_ep->bw_info;
-	const u32 esit_boundary = get_esit_boundary(sch_ep);
 	const u32 bw_boundary = get_bw_boundary(sch_ep->speed);
 	u32 offset;
 	u32 worst_bw;
@@ -621,9 +589,6 @@ static int check_sch_bw(struct mu3h_sch_ep_info *sch_ep)
 		if (ret)
 			continue;
 
-		if ((offset + sch_ep->num_budget_microframes) > esit_boundary)
-			break;
-
 		worst_bw = get_max_bw(sch_bw, sch_ep, offset);
 		if (worst_bw > bw_boundary)
 			continue;
diff --git a/drivers/usb/host/xhci-mtk.h b/drivers/usb/host/xhci-mtk.h
index ddcf25524f67..f627941c4860 100644
--- a/drivers/usb/host/xhci-mtk.h
+++ b/drivers/usb/host/xhci-mtk.h
@@ -23,6 +23,7 @@
  * bandwidth to it.
  */
 #define XHCI_MTK_MAX_ESIT	64
+#define XHCI_MTK_BW_IDX(idx)	((idx) & 63)
 
 /**
  * @fs_bus_bw: array to keep track of bandwidth already used for FS
-- 
2.32.0.605.g8dce9f2422-goog