75 lines
3.0 KiB
Diff
75 lines
3.0 KiB
Diff
From 9d604ddc4770f8f25de148e9b35687817a5d4110 Mon Sep 17 00:00:00 2001
|
|
From: Hans de Goede <hdegoede@redhat.com>
|
|
Date: Wed, 28 Mar 2012 20:31:32 +0200
|
|
Subject: [PATCH 141/146] usb-ehci: frindex always is a 14 bits counter
|
|
|
|
frindex always is a 14 bits counter, and not a 13 bits one as we were
|
|
emulating. There are some subtle hints to this in the spec, first of all
|
|
"Table 2-12. FRINDEX - Frame Index Register" says:
|
|
"Bit 13:0 Frame Index. The value in this register increments at the end of
|
|
each time frame (e.g. micro-frame). Bits [N:3] are used for the Frame List
|
|
current index. This means that each location of the frame list is accessed
|
|
8 times (frames or micro-frames) before moving to the next index. The
|
|
following illustrates values of N based on the value of the Frame List
|
|
Size field in the USBCMD register.
|
|
|
|
USBCMD[Frame List Size] Number Elements N
|
|
00b 1024 12
|
|
01b 512 11
|
|
10b 256 10
|
|
11b Reserved"
|
|
|
|
Notice how the text talks about "Bits [N:3]" are used ..., it does
|
|
NOT say that when N == 12 (our case) the counter will wrap from 8191 to 0,
|
|
or in otherwords that it is a 13 bits counter (bits 0 - 12).
|
|
|
|
The other hint is in "Table 2-10. USBSTS USB Status Register Bit Definitions":
|
|
|
|
"Bit 3 Frame List Rollover - R/WC. The Host Controller sets this bit to a one
|
|
when the Frame List Index (see Section 2.3.4) rolls over from its maximum value
|
|
to zero. The exact value at which the rollover occurs depends on the frame
|
|
list size. For example, if the frame list size (as programmed in the Frame
|
|
List Size field of the USBCMD register) is 1024, the Frame Index Register
|
|
rolls over every time FRINDEX[13] toggles. Similarly, if the size is 512,
|
|
the Host Controller sets this bit to a one every time FRINDEX[12] toggles."
|
|
|
|
Notice how this text talks about setting bit 3 when bit 13 of frindex toggles
|
|
(when there are 1024 entries, so our case), so this indicates that frindex
|
|
has a bit 13 making it a 14 bit counter.
|
|
|
|
Besides these clear hints the real proof is in the pudding. Before this
|
|
patch I could not stream data from a USB2 webcam under Windows XP, after
|
|
this cam using a USB2 webcam under Windows XP works fine, and no regressions
|
|
with other operating systems were seen.
|
|
|
|
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
|
|
---
|
|
hw/usb-ehci.c | 8 ++++++--
|
|
1 file changed, 6 insertions(+), 2 deletions(-)
|
|
|
|
diff --git a/hw/usb-ehci.c b/hw/usb-ehci.c
|
|
index b5d7037..3934bf0 100644
|
|
--- a/hw/usb-ehci.c
|
|
+++ b/hw/usb-ehci.c
|
|
@@ -2157,11 +2157,15 @@ static void ehci_frame_timer(void *opaque)
|
|
if ( !(ehci->usbsts & USBSTS_HALT)) {
|
|
ehci->frindex += 8;
|
|
|
|
- if (ehci->frindex > 0x00001fff) {
|
|
- ehci->frindex = 0;
|
|
+ if (ehci->frindex == 0x00002000) {
|
|
ehci_set_interrupt(ehci, USBSTS_FLR);
|
|
}
|
|
|
|
+ if (ehci->frindex == 0x00004000) {
|
|
+ ehci_set_interrupt(ehci, USBSTS_FLR);
|
|
+ ehci->frindex = 0;
|
|
+ }
|
|
+
|
|
ehci->sofv = (ehci->frindex - 1) >> 3;
|
|
ehci->sofv &= 0x000003ff;
|
|
}
|
|
--
|
|
1.7.9.3
|
|
|