Date: Mon, 9 Nov 2015 13:30:55 +0100 From: Hans Petter Selasky <hps@selasky.org> To: =?UTF-8?Q?Roger_Pau_Monn=c3=a9?= <royger@FreeBSD.org>, src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org Subject: Re: svn commit: r290610 - head/sys/x86/x86 Message-ID: <564091FF.8090605@selasky.org> In-Reply-To: <201511091219.tA9CJwe7067036@repo.freebsd.org> References: <201511091219.tA9CJwe7067036@repo.freebsd.org>
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On 11/09/15 13:19, Roger Pau Monné wrote:
> + if (dmat->common.flags & BUS_DMA_KEEP_PG_OFFSET) {
> + /*
> + * If we have to keep the offset of each page this function
> + * is not suitable, switch back to bus_dmamap_load_ma_triv
> + * which is going to do the right thing in this case.
> + */
> + error = bus_dmamap_load_ma_triv(dmat, map, ma, buflen, ma_offs,
> + flags, segs, segp);
> + return (error);
> + }
Hi,
There has been an update made to the USB stack, which is currently the
only client of "BUS_DMA_KEEP_PG_OFFSET", which means this check can
probably be skipped or relaxed a bit. The condition which must be
fullfilled is:
#ifdef USB_DEBUG
if (nseg > 1 &&
((segs->ds_addr + segs->ds_len) & (USB_PAGE_SIZE - 1)) !=
((segs + 1)->ds_addr & (USB_PAGE_SIZE - 1))) {
/*
* This check verifies there is no page offset hole
* between the first and second segment. See the
* BUS_DMA_KEEP_PG_OFFSET flag.
*/
DPRINTFN(0, "Page offset was not preserved\n");
error = 1;
goto done;
}
#endif
See: sys/dev/usb/usb_busdma.c
--HPS
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