USB: musb: use right poll limit for low speed devices

Remove wrongly applied upper limit on the interrupt transfer
interval for low speed devices (not much of an error per se,
according to USB specs).

Signed-off-by: Sergei Shtylyov <sshtylyov@ru.mvista.com>
Signed-off-by: David Brownell <dbrownell@users.sourceforge.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@suse.de>

diff --git a/drivers/usb/musb/musb_host.c b/drivers/usb/musb/musb_host.c
index 23d3890fd54de9d5a8a1334d511b129e3f0c6fa2..6dbbd0786a6a0955877dca888f107b641d50eec0 100644 (file)
--- a/drivers/usb/musb/musb_host.c
+++ b/drivers/usb/musb/musb_host.c
@@ -1863,19 +1863,21 @@ static int musb_urb_enqueue(
        }
        qh->type_reg = type_reg;
 
-       /* precompute rxinterval/txinterval register */
-       interval = min((u8)16, epd->bInterval); /* log encoding */
+       /* Precompute RXINTERVAL/TXINTERVAL register */
        switch (qh->type) {
        case USB_ENDPOINT_XFER_INT:
-               /* fullspeed uses linear encoding */
-               if (USB_SPEED_FULL == urb->dev->speed) {
-                       interval = epd->bInterval;
-                       if (!interval)
-                               interval = 1;
+               /*
+                * Full/low speeds use the  linear encoding,
+                * high speed uses the logarithmic encoding.
+                */
+               if (urb->dev->speed <= USB_SPEED_FULL) {
+                       interval = max_t(u8, epd->bInterval, 1);
+                       break;
                }
                /* FALLTHROUGH */
        case USB_ENDPOINT_XFER_ISOC:
-               /* iso always uses log encoding */
+               /* ISO always uses logarithmic encoding */
+               interval = min_t(u8, epd->bInterval, 16);
                break;
        default:
                /* REVISIT we actually want to use NAK limits, hinting to the