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