linux-kernel - [PATCH 2/2] usb: xhci-mtk: fix random remote wakeup

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Date:   Tue, 2 Nov 2021 10:50:04 +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 2/2] usb: xhci-mtk: fix random remote wakeup

Some platforms, e.g. 8183/8192, use low level latch way to keep
wakeup signal, it may latch a wrong signal if debounce more time,
and enable wakeup function earlier.
                   ____________________
ip_sleep      ____/                    \_____________
                           ___________________
wakeup_signal ____________/                   \______
                      _______________________________
wakeup_en     _______/
                      ^     ^
                      |(1)  |(2)
latch wakeup_signal mistakenly at (1), should latch it at (2);

Workaround: delay about 100us to enable wakeup, meanwhile decrease
debounce time.

Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
---
 drivers/usb/host/xhci-mtk.c | 11 ++++++-----
 1 file changed, 6 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/host/xhci-mtk.c b/drivers/usb/host/xhci-mtk.c
index adc5debcde88..91a664e8810d 100644
--- a/drivers/usb/host/xhci-mtk.c
+++ b/drivers/usb/host/xhci-mtk.c
@@ -245,11 +245,12 @@ static int xhci_mtk_host_disable(struct xhci_hcd_mtk *mtk)
 	/* wait for host ip to sleep */
 	ret = readl_poll_timeout(&ippc->ip_pw_sts1, value,
 			  (value & STS1_IP_SLEEP_STS), 100, 100000);
-	if (ret) {
+	if (ret)
 		dev_err(mtk->dev, "ip sleep failed!!!\n");
-		return ret;
-	}
-	return 0;
+	else /* workaound for platforms using low level latch */
+		usleep_range(100, 200);
+
+	return ret;
 }
 
 static int xhci_mtk_ssusb_config(struct xhci_hcd_mtk *mtk)
@@ -300,7 +301,7 @@ static void usb_wakeup_ip_sleep_set(struct xhci_hcd_mtk *mtk, bool enable)
 	case SSUSB_UWK_V1_1:
 		reg = mtk->uwk_reg_base + PERI_WK_CTRL0;
 		msk = WC0_IS_EN | WC0_IS_C(0xf) | WC0_IS_P;
-		val = enable ? (WC0_IS_EN | WC0_IS_C(0x8)) : 0;
+		val = enable ? (WC0_IS_EN | WC0_IS_C(0x1)) : 0;
 		break;
 	case SSUSB_UWK_V1_2:
 		reg = mtk->uwk_reg_base + PERI_WK_CTRL0;
-- 
2.18.0