usb: block suspension of superspeed port while hispeed peer is active

ClearPortFeature(PORT_POWER) on a usb3 port places the port in either a
DSPORT.Powered-off-detect / DSPORT.Powered-off-reset loop, or the
DSPORT.Powered-off state.  There is no way to ensure that RX
terminations will persist in this state, so it is possible a device will
degrade to its usb2 connection.  Prevent this by blocking power-off of a
usb3 port while its usb2 peer is active, and powering on a usb3 port
before its usb2 peer.

By default the latency between peer power-on events is 0.  In order for
the device to not see usb2 active while usb3 is still powering up inject
the hub recommended power_on_good delay.  In support of satisfying the
power_on_good delay outside of hub_power_on() refactor the places where
the delay is consumed to call a new hub_power_on_good_delay() helper.

Finally, because this introduces several new checks for whether a port
is_superspeed, cache that disctinction at port creation so that we don't
need to keep looking up the parent hub device.

Acked-by: Alan Stern <stern@rowland.harvard.edu>
[alan]: add a 'superspeed' flag to the port
Signed-off-by: Dan Williams <dan.j.williams@intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 15 insertions, 0 deletions

diff --git a/drivers/usb/core/hub.h b/drivers/usb/core/hub.h
index 3ef1c2e435cc..906c355e0631 100644
--- a/drivers/usb/core/hub.h
+++ b/drivers/usb/core/hub.h
@@ -89,6 +89,7 @@ struct usb_hub {
  * @connect_type: port's connect type
  * @location: opaque representation of platform connector location
  * @portnum: port index num based one
+ * @is_superspeed cache super-speed status
  */
 struct usb_port {
 	struct usb_device *child;
@@ -98,6 +99,7 @@ struct usb_port {
 	enum usb_port_connect_type connect_type;
 	usb_port_location_t location;
 	u8 portnum;
+	unsigned int is_superspeed:1;
 };
 
 #define to_usb_port(_dev) \
@@ -125,6 +127,19 @@ static inline bool hub_is_port_power_switchable(struct usb_hub *hub)
 	return (le16_to_cpu(hcs) & HUB_CHAR_LPSM) < HUB_CHAR_NO_LPSM;
 }
 
+static inline int hub_is_superspeed(struct usb_device *hdev)
+{
+	return hdev->descriptor.bDeviceProtocol == USB_HUB_PR_SS;
+}
+
+static inline unsigned hub_power_on_good_delay(struct usb_hub *hub)
+{
+	unsigned delay = hub->descriptor->bPwrOn2PwrGood * 2;
+
+	/* Wait at least 100 msec for power to become stable */
+	return max(delay, 100U);
+}
+
 static inline int hub_port_debounce_be_connected(struct usb_hub *hub,
 		int port1)
 {