usb: hub: fix power good delay timing

usb_hub_power_on() currently waits for the maximum of (a) the hub port's
power output to become good, (b) the max time the USB specification
allows a device to take to connect.

However, these two operations must occur in series rather than in
parallel. First, the power supply ramps up to the level required to
power the USB device, and then the device may take a certain amount of
time to connect (assert D+/D- pullups).

Related, the maximum time that a device has to assert pullups is 1s not
100ms.

This is explained in "Connect Timing ECN.pdf", itself part of
usb_20_042814.zip from www.usb.org.

Signed-off-by: Stephen Warren <swarren@nvidia.com>

diff --git a/common/usb_hub.c b/common/usb_hub.c
index ffac0e743cef38f2c98cb7a8c58d40acd5097516..4875a51aceaf14347a75924fb6225d6151732039 100644 (file)
--- a/common/usb_hub.c
+++ b/common/usb_hub.c
@@ -36,7 +36,7 @@
 #endif
 
 #ifndef CONFIG_USB_HUB_MIN_POWER_ON_DELAY
-#define CONFIG_USB_HUB_MIN_POWER_ON_DELAY      100
+#define CONFIG_USB_HUB_MIN_POWER_ON_DELAY      1000
 #endif
 
 #define USB_BUFSIZ     512
@@ -138,8 +138,11 @@ static void usb_hub_power_on(struct usb_hub_device *hub)
                debug("port %d returns %lX\n", i + 1, dev->status);
        }
 
-       /* Wait for power to become stable */
-       mdelay(max(pgood_delay, CONFIG_USB_HUB_MIN_POWER_ON_DELAY));
+       /*
+        * Wait for power to become stable,
+        * plus spec-defined max time for device to connect
+        */
+       mdelay(pgood_delay + CONFIG_USB_HUB_MIN_POWER_ON_DELAY);
 }
 
 void usb_hub_reset(void)