From: Alan Stern <stern@rowland.harvard.edu>
Date: Wed, 30 Jan 2013 21:36:40 +0000 (-0500)
Subject: USB: EHCI: fix bug in scheduling periodic split transfers
X-Git-Tag: firefly_0821_release~7541^2~39
X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=f3f2759e76bfbd10f1612cf7f3d9d6e16fee1782;p=firefly-linux-kernel-4.4.55.git
USB: EHCI: fix bug in scheduling periodic split transfers
commit 3e619d04159be54b3daa0b7036b0ce9e067f4b5d upstream.
This patch (as1654) fixes a very old bug in ehci-hcd, connected with
scheduling of periodic split transfers. The calculations for
full/low-speed bus usage are all carried out after the correction for
bit-stuffing has been applied, but the values in the max_tt_usecs
array assume it hasn't been. The array should allow for allocation of
up to 90% of the bus capacity, which is 900 us, not 780 us.
The symptom caused by this bug is that any isochronous transfer to a
full-speed device with a maxpacket size larger than about 980 bytes is
always rejected with a -ENOSPC error.
Signed-off-by: Alan Stern <stern@rowland.harvard.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
diff --git a/drivers/usb/host/ehci-sched.c b/drivers/usb/host/ehci-sched.c
index 8949b239decc..53192f2e2c75 100644
--- a/drivers/usb/host/ehci-sched.c
+++ b/drivers/usb/host/ehci-sched.c
@@ -236,7 +236,7 @@ static inline unsigned char tt_start_uframe(struct ehci_hcd *ehci, __hc32 mask)
}
static const unsigned char
-max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 30, 0 };
+max_tt_usecs[] = { 125, 125, 125, 125, 125, 125, 125, 25 };
/* carryover low/fullspeed bandwidth that crosses uframe boundries */
static inline void carryover_tt_bandwidth(unsigned short tt_usecs[8])