phy: apple: atc: Initialize USB2 PHY for host mode during probe

Now that the upstream Type-C PHY code is getting wider testing we got
reports of USB devices plugged in during boot or those plugged in for
the first time after boot occasionally not working correctly.

For yet to determined reasons this issue disappears if the USB2 PHY is
brought up for USB host mode once during probe. This could be related to
the bootloader (m1n1) initializing the USB-C ports for device mode in
our test environment. On the other hand Sven has discovered that MacOS
sets dwc3 (but not xhci) up and tears it immediately down during boot
even if no device is connected.

Reported-by: James Calligeros <jcalligeros99@gmail.com>
Reported-by: Sven Peter <sven@kernel.org>
Fixes: 8e98ca1 ("phy: apple: Add Apple Type-C PHY")
Signed-off-by: Janne Grunau <j@jannau.net>

Author: jannau

drivers/phy/apple/atc.c

@@ -1788,12 +1788,8 @@ static int atcphy_configure(struct apple_atcphy *atcphy, enum atcphy_mode mode)
 	return 0;
 }
 
-static int atcphy_usb2_set_mode(struct phy *phy, enum phy_mode mode, int submode)
+static int _atcphy_usb2_set_mode(struct apple_atcphy *atcphy, enum phy_mode mode)
 {
-	struct apple_atcphy *atcphy = phy_get_drvdata(phy);
-
-	guard(mutex)(&atcphy->lock);
-
 	switch (mode) {
 	case PHY_MODE_USB_HOST:
 		set32(atcphy->regs.usb2phy + USB2PHY_SIG, USB2PHY_SIG_HOST);
@@ -1808,6 +1804,15 @@ static int atcphy_usb2_set_mode(struct phy *phy, enum phy_mode mode, int submode
 	return 0;
 }
 
+static int atcphy_usb2_set_mode(struct phy *phy, enum phy_mode mode, int submode)
+{
+	struct apple_atcphy *atcphy = phy_get_drvdata(phy);
+
+	guard(mutex)(&atcphy->lock);
+
+	return _atcphy_usb2_set_mode(atcphy, mode);
+}
+
 static const struct phy_ops apple_atc_usb2_phy_ops = {
 	.owner = THIS_MODULE,
 	.set_mode = atcphy_usb2_set_mode,
@@ -2226,6 +2231,14 @@ static int atcphy_probe_finalize(struct apple_atcphy *atcphy)
 	/* Reset dwc3 on probe, let dwc3 (consumer) deassert it */
 	_atcphy_dwc3_reset_assert(atcphy);
 
+	/*
+	 * Bring the USB2 up once in host mode. For not yet understood reasons
+	 * this avoids not detecting USB devices on the initial cold or hot
+	 * plug.
+	 */
+	atcphy_usb2_power_on(atcphy);
+	_atcphy_usb2_set_mode(atcphy, PHY_MODE_USB_HOST);
+
 	/* Reset atcphy to clear any state potentially left by the bootloader */
 	atcphy_usb2_power_off(atcphy);
 	atcphy_power_off(atcphy);