linux-kernel - [PATCH next 1/2] usb: xhci-mtk: fix wrong remainder of bandwidth budget

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Date:   Wed, 31 Mar 2021 16:25:41 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     Mathias Nyman <mathias.nyman@...el.com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>
CC:     Chunfeng Yun <chunfeng.yun@...iatek.com>,
        Matthias Brugger <matthias.bgg@...il.com>,
        <linux-usb@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-mediatek@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>
Subject: [PATCH next 1/2] usb: xhci-mtk: fix wrong remainder of bandwidth budget

The remainder of the last bandwidth bugdget is wrong,
it's the value alloacted in last bugdget, not unused.

Reported-by: Yaqii Wu <Yaqii.Wu@...iatek.com>
Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
---
 drivers/usb/host/xhci-mtk-sch.c | 7 ++-----
 1 file changed, 2 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-mtk-sch.c b/drivers/usb/host/xhci-mtk-sch.c
index a59d1f6d4744..7ac76ae28998 100644
--- a/drivers/usb/host/xhci-mtk-sch.c
+++ b/drivers/usb/host/xhci-mtk-sch.c
@@ -341,7 +341,6 @@ static void setup_sch_info(struct xhci_ep_ctx *ep_ctx,
 		}
 
 		if (ep_type == ISOC_IN_EP || ep_type == ISOC_OUT_EP) {
-			u32 remainder;
 
 			if (sch_ep->esit == 1)
 				sch_ep->pkts = esit_pkts;
@@ -357,14 +356,12 @@ static void setup_sch_info(struct xhci_ep_ctx *ep_ctx,
 			sch_ep->repeat = !!(sch_ep->num_budget_microframes > 1);
 			sch_ep->bw_cost_per_microframe = maxpkt * sch_ep->pkts;
 
-			remainder = sch_ep->bw_cost_per_microframe;
-			remainder *= sch_ep->num_budget_microframes;
-			remainder -= (maxpkt * esit_pkts);
 			for (i = 0; i < sch_ep->num_budget_microframes - 1; i++)
 				bwb_table[i] = sch_ep->bw_cost_per_microframe;
 
 			/* last one <= bw_cost_per_microframe */
-			bwb_table[i] = remainder;
+			bwb_table[i] = maxpkt * esit_pkts
+				       - i * sch_ep->bw_cost_per_microframe;
 		}
 	} else if (is_fs_or_ls(sch_ep->speed)) {
 		sch_ep->pkts = 1; /* at most one packet for each microframe */
-- 
2.18.0