25 Aug
2011
25 Aug
'11
4 p.m.
- if (frame_diff < 0)
frame_diff += 1024; /* handle 10-bit wrap-around */After reading through some HCD source files, I deduced the following wrap-arounds:
EHCI: 8-10 bits (default 9) FHCI: 11 bits IMX21: 16 bits ISP1760: 10 bits OHCI: 16 bits OXU210HP: 10 bits R8A66597: 10 bits SL811: 5 bits(!?) UHCI: 32 bits xHCI: ?
As long as there isn't an API that tells us about the valid range of the frame counter, we should probably mask off all except the lowest few bits.
Argh. Good catch, thanks for looking into this. If we only used the 8 least-significant bits, it'd still leave us with up to 256 ms. That should work I guess. But the SL811 with 5 bits is a problem, that makes 32ms, this is probably too low. In that case we'd need to fall back to the existing scheme and ignore the frame counter information. -Pierre