linux-kernel - [PATCH v1 1/8] usb: phy: tegra: Add delay after power up

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Message-Id: <20201215202113.30394-2-digetx@gmail.com>
Date:   Tue, 15 Dec 2020 23:21:06 +0300
From:   Dmitry Osipenko <digetx@...il.com>
To:     Thierry Reding <thierry.reding@...il.com>,
        Jonathan Hunter <jonathanh@...dia.com>,
        Peter Chen <Peter.Chen@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Alan Stern <stern@...land.harvard.edu>,
        Felipe Balbi <balbi@...nel.org>,
        Matt Merhar <mattmerhar@...tonmail.com>,
        Nicolas Chauvet <kwizart@...il.com>,
        Peter Geis <pgwipeout@...il.com>
Cc:     linux-tegra@...r.kernel.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH v1 1/8] usb: phy: tegra: Add delay after power up

The PHY hardware needs the delay of 2ms after power up, otherwise initial
interrupt may be lost if USB controller is accessed before PHY is settled
down. Previously this issue was masked by implicit delays, but now it pops
up after squashing the older ehci-tegra driver into the ChipIdea driver.

Tested-by: Matt Merhar <mattmerhar@...tonmail.com>
Tested-by: Nicolas Chauvet <kwizart@...il.com>
Tested-by: Peter Geis <pgwipeout@...il.com>
Signed-off-by: Dmitry Osipenko <digetx@...il.com>
---
 drivers/usb/phy/phy-tegra-usb.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/usb/phy/phy-tegra-usb.c b/drivers/usb/phy/phy-tegra-usb.c
index 03a333797382..cee9c9dbb775 100644
--- a/drivers/usb/phy/phy-tegra-usb.c
+++ b/drivers/usb/phy/phy-tegra-usb.c
@@ -784,6 +784,9 @@ static int tegra_usb_phy_power_on(struct tegra_usb_phy *phy)
 
 	phy->powered_on = true;
 
+	/* let PHY to settle down */
+	usleep_range(2000, 2500);
+
 	return 0;
 }
 
-- 
2.29.2