Start with a short USB hub reset delay of 20ms. This can be enough for
some configurations. Switch to longer reset delay only if the short
delay hasn't been long enough.
This USB hub reset handling strategy is also used in the Linux kernel
USB hub driver, function hub_port_reset().
Without patch:
$ time usb
usb: USB: scanning bus for devices...
usb: 17 USB Device(s) found
time: 21750ms
With patch:
$ time usb
usb: USB: scanning bus for devices...
usb: 17 USB Device(s) found
time: 16355ms
Delta: ~5.5 seconds
Signed-off-by: Primoz Fiser <primoz.fiser@xxxxxxxxx>
---
drivers/usb/core/hub.c | 9 +++++++--
1 file changed, 7 insertions(+), 2 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c
index d01a01607..91604e1ef 100644
--- a/drivers/usb/core/hub.c
+++ b/drivers/usb/core/hub.c
@@ -30,6 +30,9 @@
#define USB_BUFSIZ 512
+#define HUB_SHORT_RESET_TIME 20
+#define HUB_LONG_RESET_TIME 200
+
static int usb_get_hub_descriptor(struct usb_device *dev, void *data, int size)
{
return usb_control_msg(dev, usb_rcvctrlpipe(dev, 0),
@@ -116,12 +119,13 @@ int hub_port_reset(struct usb_device *hub, int port, struct usb_device *usb)
int tries;
struct usb_port_status portsts;
unsigned short portstatus, portchange;
+ int delay = HUB_SHORT_RESET_TIME; /* start with short reset delay */
dev_dbg(&hub->dev, "hub_port_reset: resetting port %d...\n", port);
for (tries = 0; tries < MAX_TRIES; tries++) {
usb_set_port_feature(hub, port + 1, USB_PORT_FEAT_RESET);
- mdelay(200);
+ mdelay(delay);
if (usb_get_port_status(hub, port + 1, &portsts) < 0) {
dev_dbg(&hub->dev, "get_port_status failed status %lX\n",
@@ -148,7 +152,8 @@ int hub_port_reset(struct usb_device *hub, int port, struct usb_device *usb)
if (portstatus & USB_PORT_STAT_ENABLE)
break;
- mdelay(200);
+ /* Switch to long reset delay for the next round */
+ delay = HUB_LONG_RESET_TIME;
}
if (tries == MAX_TRIES) {
--
2.17.1
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