Date: Sat, 25 Apr 2015 07:59:50 +0200 From: Hans Petter Selasky <hps@selasky.org> To: Ian Lepore <ian@freebsd.org>, Svatopluk Kraus <onwahe@gmail.com> Cc: freebsd-current@freebsd.org Subject: Re: [patch] fix add_bounce_page() for BUS_DMA_KEEP_PG_OFFSET Message-ID: <553B2D56.1000405@selasky.org> In-Reply-To: <1429882188.1157.2.camel@freebsd.org> References: <CAFHCsPVgYHL0OyMnn1b2DcNiQO-20k1aDvJNvFjwU21YxB29Cw@mail.gmail.com> <1429882188.1157.2.camel@freebsd.org>
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On 04/24/15 15:29, Ian Lepore wrote: > On Fri, 2015-04-24 at 13:34 +0200, Svatopluk Kraus wrote: >> The add_bounce_page() can be called from _bus_dmamap_load_phys(). >> Client virtual address is zero (not valid) in that case. So, client >> physical address must be used to get an offset when >> BUS_DMA_KEEP_PG_OFFSET flag is set. Note that client physical address >> is always valid. >> >> Svatopluk Kraus > > The only user of BUS_DMA_KEEP_PG_OFFSET in the system is USB. If the > flag didn't exist, we could do bouncing with a whole lot more > efficiency, at least in the ARM world. I wonder if it would be possible > to just eliminate the flag (and of course, USB's need for it, which I > fully admit I don't understand even a little bit). > Hi, USB (EHCI/UHCI/OHCI) needs this flag when computing scatter/gather lists. Please ensure it works like expected. The good news is XHCI needs it less than the EHCI. Ian: The patch looks good - will you commit it? --HPS
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