The sunxi musb has a bug where sometimes it will generate a babble
error on device disconnect instead of a disconnect irq. When this
happens the musb-controller switches from host mode to device mode
(it clears MUSB_DEVCTL_SESSION and sets MUSB_DEVCTL_BDEVICE) and
gets stuck in this state.

Clearing this requires reporting Vbus low for 200 or more ms, but
on some devices Vbus is simply always high (host-only mode, no Vbus
control). The phy-sun4i-usb code already has code to force a session
end for devices without Vbus control.

This commit adds a sun4i_usb_phy_force_session_end() function exporting
this functionality to the sunxi-musb glue, so that it can force a session
end to fixup the stuck state after a babble error.

Signed-off-by: Hans de Goede <hdego...@redhat.com>
---
 drivers/phy/phy-sun4i-usb.c       | 11 +++++++++++
 include/linux/phy/phy-sun4i-usb.h |  7 +++++++
 2 files changed, 18 insertions(+)

diff --git a/drivers/phy/phy-sun4i-usb.c b/drivers/phy/phy-sun4i-usb.c
index 43c0d98..06f4e11a 100644
--- a/drivers/phy/phy-sun4i-usb.c
+++ b/drivers/phy/phy-sun4i-usb.c
@@ -470,6 +470,17 @@ void sun4i_usb_phy_set_squelch_detect(struct phy *_phy, 
bool enabled)
 }
 EXPORT_SYMBOL_GPL(sun4i_usb_phy_set_squelch_detect);
 
+void sun4i_usb_phy_force_session_end(struct phy *_phy)
+{
+       struct sun4i_usb_phy *phy = phy_get_drvdata(_phy);
+       struct sun4i_usb_phy_data *data = to_sun4i_usb_phy_data(phy);
+
+       data->id_det = -1;
+       data->force_session_end = true;
+       queue_delayed_work(system_wq, &data->detect, 0);
+}
+EXPORT_SYMBOL_GPL(sun4i_usb_phy_force_session_end);
+
 static const struct phy_ops sun4i_usb_phy_ops = {
        .init           = sun4i_usb_phy_init,
        .exit           = sun4i_usb_phy_exit,
diff --git a/include/linux/phy/phy-sun4i-usb.h 
b/include/linux/phy/phy-sun4i-usb.h
index 50aed92..3bb773f 100644
--- a/include/linux/phy/phy-sun4i-usb.h
+++ b/include/linux/phy/phy-sun4i-usb.h
@@ -23,4 +23,11 @@
  */
 void sun4i_usb_phy_set_squelch_detect(struct phy *phy, bool enabled);
 
+/**
+ * sun4i_usb_force_session_end() - Force the current session to end
+ *                                by reporting VBus low for 200+ ms
+ * @phy: reference to a sun4i usb phy
+ */
+void sun4i_usb_phy_force_session_end(struct phy *phy);
+
 #endif
-- 
2.9.3

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