Date: Thu, 26 Nov 2020 17:43:13 +0100 From: Hans Petter Selasky <hps@selasky.org> To: Thomas Steen Rasmussen <thomas@gibfest.dk> Cc: usb@freebsd.org Subject: Re: webcamd, usb and two webcams - only one works Message-ID: <1d1fdacc-453c-b4db-1879-5f1609093e50@selasky.org> In-Reply-To: <ade99dc2-a080-9da7-34c4-d8c2ffaa53d8@gibfest.dk> References: <c11c1a2f-306f-3cd9-825f-4c39fd250d50@gibfest.dk> <9a382539-c90d-91b9-bfac-f36c0f19d3f7@selasky.org> <723be24d-b2fe-85df-4961-5483004050e8@gibfest.dk> <f49afce8-e055-d432-b374-4af10bf7d70e@selasky.org> <cdadc525-e4f9-6cde-26f3-15d7594bd5ee@gibfest.dk> <6c527c1f-62a6-3089-50b8-02cda74b4eb1@selasky.org> <13180470-0336-b115-ce31-bc392ff8da76@gibfest.dk> <638a1059-f8dc-59c5-21ff-aabc380cac28@selasky.org> <0330eee1-e22c-82b9-1c50-4e8c42bf9466@gibfest.dk> <2338ae76-aa3e-8ee6-1cda-f12ec6cf9648@selasky.org> <ade99dc2-a080-9da7-34c4-d8c2ffaa53d8@gibfest.dk>
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On 11/26/20 5:05 PM, Thomas Steen Rasmussen wrote: > > I see. What does this mean? > > Since the same problem is also on different computer, intel instead of AMD. > > Same problem also occurred when I replaced one of the webcams with a > different model. > > It isn't clear to me whether this is a problem/bug in one or more of the > webcams or drivers, or in freebsd or somewhere else? > > Thank you for your time and patience with this :) Hi, The xHCI controller has some logic to reserve bandwidth in bytes per frame (125us for High speed or 1ms for Full speed) for various endpoints. If these numbers are wrong the xHCI controller may think there is no bandwidth and will not activate the endpoint and schedule the transactions. Maybe my Skylake xHCI doesn't care about these values :-( Reference: https://www.intel.com/content/dam/www/public/us/en/documents/technical-specifications/extensible-host-controler-interface-usb-xhci.pdf --HPS
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