1 files changed, 6 insertions, 5 deletions

diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index ebcca9700671..88419c6823a8 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -707,6 +707,7 @@ iso_stream_init (
         } else {
                 u32             addr;
                 int             think_time;
+                int             hs_transfers;
 
                 addr = dev->ttport << 24;
                 if (!ehci_is_TDI(ehci)
@@ -719,6 +720,7 @@ iso_stream_init (
                 think_time = dev->tt ? dev->tt->think_time : 0;
                 stream->tt_usecs = NS_TO_US (think_time + usb_calc_bus_time (
                                 dev->speed, is_input, 1, maxp));
+                hs_transfers = max (1u, (maxp + 187) / 188);
                 if (is_input) {
                         u32     tmp;
 
@@ -727,12 +729,11 @@ iso_stream_init (
                         stream->usecs = HS_USECS_ISO (1);
                         stream->raw_mask = 1;
 
-                        /* pessimistic c-mask */
-                        tmp = usb_calc_bus_time (USB_SPEED_FULL, 1, 0, maxp)
-                                        / (125 * 1000);
-                        stream->raw_mask |= 3 << (tmp + 9);
+                        /* c-mask as specified in USB 2.0 11.18.4 3.c */
+                        tmp = (1 << (hs_transfers + 2)) - 1;
+                        stream->raw_mask |= tmp << (8 + 2);
                 } else
-                        stream->raw_mask = smask_out [maxp / 188];
+                        stream->raw_mask = smask_out [hs_transfers - 1];
                 bandwidth = stream->usecs + stream->c_usecs;
                 bandwidth /= 1 << (interval + 2);