linux-kernel - [PATCH next 2/2] usb: mtu3: fix random remote wakeup

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Date:   Thu, 26 Aug 2021 16:36:37 +0800
From:   Chunfeng Yun <chunfeng.yun@...iatek.com>
To:     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>,
        Eddie Hung <eddie.hung@...iatek.com>, <stable@...r.kernel.org>
Subject: [PATCH next 2/2] usb: mtu3: 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 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.

Fixes: b1a344589eea ("usb: mtu3: support ip-sleep wakeup for MT8183")
Cc: stable@...r.kernel.org
Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
---
 drivers/usb/mtu3/mtu3_host.c | 2 +-
 drivers/usb/mtu3/mtu3_plat.c | 3 +++
 2 files changed, 4 insertions(+), 1 deletion(-)

diff --git a/drivers/usb/mtu3/mtu3_host.c b/drivers/usb/mtu3/mtu3_host.c
index 7d528f3c2482..f3903367a6a0 100644
--- a/drivers/usb/mtu3/mtu3_host.c
+++ b/drivers/usb/mtu3/mtu3_host.c
@@ -62,7 +62,7 @@ static void ssusb_wakeup_ip_sleep_set(struct ssusb_mtk *ssusb, bool enable)
 	case SSUSB_UWK_V1_1:
 		reg = ssusb->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 = ssusb->uwk_reg_base + PERI_WK_CTRL0;
diff --git a/drivers/usb/mtu3/mtu3_plat.c b/drivers/usb/mtu3/mtu3_plat.c
index 5b3f7f73cb40..f13531022f4a 100644
--- a/drivers/usb/mtu3/mtu3_plat.c
+++ b/drivers/usb/mtu3/mtu3_plat.c
@@ -63,6 +63,9 @@ static int wait_for_ip_sleep(struct ssusb_mtk *ssusb)
 	if (ret) {
 		dev_err(ssusb->dev, "ip sleep failed!!!\n");
 		ret = -EBUSY;
+	} else {
+		/* workaround: avoid wrong wakeup signal latch for some soc */
+		usleep_range(100, 200);
 	}
 
 	return ret;
-- 
2.18.0