phy: sun4i-usb: Add a sunxi specific function for setting squelch-detect

The sunxi otg phy has a bug where it wrongly detects a high speed squelch
when reset on the root port gets de-asserted with a lo-speed device.

The workaround for this is to disable squelch detect before de-asserting
reset, and re-enabling it after the reset de-assert is done. Add a sunxi
specific phy function to allow the sunxi-musb glue to do this.
Acked-by: NKishon Vijay Abraham I <kishon@ti.com>
Signed-off-by: NHans de Goede <hdegoede@redhat.com>
Signed-off-by: NFelipe Balbi <balbi@ti.com>

drivers/phy/phy-sun4i-usb.c

@@ -30,6 +30,7 @@
 #include <linux/of.h>
 #include <linux/of_address.h>
 #include <linux/phy/phy.h>
+#include <linux/phy/phy-sun4i-usb.h>
 #include <linux/platform_device.h>
 #include <linux/regulator/consumer.h>
 #include <linux/reset.h>
@@ -58,6 +59,7 @@
 #define PHY_OTG_FUNC_EN			0x28
 #define PHY_VBUS_DET_EN			0x29
 #define PHY_DISCON_TH_SEL		0x2a
+#define PHY_SQUELCH_DETECT		0x3c
 
 #define MAX_PHYS			3
 
@@ -204,6 +206,13 @@ static int sun4i_usb_phy_power_off(struct phy *_phy)
 	return 0;
 }
 
+void sun4i_usb_phy_set_squelch_detect(struct phy *_phy, bool enabled)
+{
+	struct sun4i_usb_phy *phy = phy_get_drvdata(_phy);
+
+	sun4i_usb_phy_write(phy, PHY_SQUELCH_DETECT, enabled ? 0 : 2, 2);
+}
+
 static struct phy_ops sun4i_usb_phy_ops = {
 	.init		= sun4i_usb_phy_init,
 	.exit		= sun4i_usb_phy_exit,

include/linux/phy/phy-sun4i-usb.h

+/*
+ * Copyright (c) 2015 Hans de Goede <hdegoede@redhat.com>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License version 2 and
+ * only version 2 as published by the Free Software Foundation.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#ifndef PHY_SUN4I_USB_H_
+#define PHY_SUN4I_USB_H_
+
+#include "phy.h"
+
+/**
+ * sun4i_usb_phy_set_squelch_detect() - Enable/disable squelch detect
+ * @phy: reference to a sun4i usb phy
+ * @enabled: wether to enable or disable squelch detect
+ */
+void sun4i_usb_phy_set_squelch_detect(struct phy *phy, bool enabled);
+
+#endif