Date: Sun, 30 Dec 2012 11:28:37 -0700 From: Ian Lepore <freebsd@damnhippie.dyndns.org> To: Scott Long <scott4long@yahoo.com> Cc: powerpc@freebsd.org, marcel@freebsd.org, mips@freebsd.org, "mav@freebsd.org Motin" <mav@freebsd.org>, "attilio@FreeBSD.org Rao" <attilio@freebsd.org>, Jeff Roberson <jroberson@jroberson.net>, sparc64@freebsd.org, arm@freebsd.org, kib@freebsd.org Subject: Re: Call for testing and review, busdma changes Message-ID: <1356892117.54953.37.camel@revolution.hippie.lan> In-Reply-To: <30DCC8A9-8E26-4500-AF33-2D81981B554F@yahoo.com> References: <alpine.BSF.2.00.1212080841370.4081@desktop> <1355077061.87661.320.camel@revolution.hippie.lan> <alpine.BSF.2.00.1212090840080.4081@desktop> <1355085250.87661.345.camel@revolution.hippie.lan> <alpine.BSF.2.00.1212231418120.2005@desktop> <1356381775.1129.181.camel@revolution.hippie.lan> <alpine.BSF.2.00.1212241104040.2005@desktop> <1356390225.1129.217.camel@revolution.hippie.lan> <2D98F70D-4031-4860-BABB-1F4663896234@yahoo.com> <1356891693.54953.31.camel@revolution.hippie.lan> <30DCC8A9-8E26-4500-AF33-2D81981B554F@yahoo.com>
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On Sun, 2012-12-30 at 11:23 -0700, Scott Long wrote: > On Dec 30, 2012, at 11:21 AM, Ian Lepore <freebsd@damnhippie.dyndns.org> wrote: > > > On Mon, 2012-12-24 at 22:13 -0500, Scott Long wrote: > >>>>> > >>>>> Still unresolved is what to do about the remaining cases -- attempts to > >>>>> do dma in arbitrary buffers not obtained from bus_dmamem_alloc() which > >>>>> are not aligned and padded appropriately. There was some discussion a > >>>>> while back, but no clear resolution. I decided not to get bogged down > >>>>> by that fact and to fix the mbuf and allocated-buffer situations that we > >>>>> know how to deal with for now. > >>>> > >> > >> Why would these allocations not be handled as normal dynamic buffers > >> would with bus_dmamap_load()? > >> > >> Scott > > > > That's my point -- for "normal dynamic buffers" (that is, they weren't > > obtained from bus_dmamem_alloc() and they aren't mbufs) which can have > > arbitrary alignment and padding in relation to cache line boundaries -- > > we don't handle them correctly now unless they're accidentally already > > aligned and sized to the right boundaries. What's unresolved is how to > > handle them correctly if they're not aligned/padded, that is, what to do > > about them that avoids needing a partial cacheline flush at sync time. > > > > Alignment is already handled. > > Scott > No it's not. -- Ian
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