Date: Sat, 8 Nov 2008 13:53:09 +0100 From: Hans Petter Selasky <hselasky@c2i.net> To: freebsd-usb@freebsd.org Cc: freebsd-current@freebsd.org Subject: Re: (FWD) Serious busdma bug in -current in relation to USB harware. Message-ID: <200811081353.09697.hselasky@c2i.net> In-Reply-To: <200811081023.10058.hselasky@freebsd.org> References: <20081107082740.GA1334@icarus.home.lan> <20081108001128.GA1437@icarus.home.lan> <200811081023.10058.hselasky@freebsd.org>
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On Saturday 08 November 2008, Alexander Motin wrote: > Hans Petter Selasky wrote: > > http://perforce.freebsd.org/chv.cgi?CH=152649 > > > > Change 152649 by hselasky@hselasky_laptop001 on 2008/11/08 09:09:50 > > > > > > Fix a serious BUSDMA bug: The initial virtual page offset is > > not retained on the bounce pages, which is what the EHCI and > > the OHCI expects. > > I'm sorry, but are you sure with this? If bounce page will have the same > page offset as original data, then how bus_dma_tag_create()'s alignment > parameter expected to work? What if data are misaligned, but hardware > require alignment? Hi, I'm not saying that my patch is fully correct for all cases, but at least it solves the USB case. USB uses an alignment of 1-byte for data. Probably someone needs to sit down a think this through. Like it is now, it is very scary with regard to USB! Maybe it is time to create a new busdma tag flag? BUS_DMA_NOREALIGN? If this flag is set, busdma should refuse to load the memory if the memory is not aligned already to the given aligment in the DMA tag ? --HPS
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