Date: Mon, 27 Aug 2012 08:06:57 +0200 From: =?windows-1252?Q?Hans_Petter_Selasky?= <hans.petter.selasky@bitfrost.no> To: =?windows-1252?Q?Ian_Lepore?= <freebsd@damnhippie.dyndns.org>, =?windows-1252?Q?Warner_Losh?= <imp@bsdimp.com> Cc: "=?windows-1252?Q?freebsd-arm=40freebsd.org?=" <freebsd-arm@freebsd.org>, "=?windows-1252?Q?freebsd-mips=40freebsd.org?=" <freebsd-mips@freebsd.org>, "=?windows-1252?Q?freebsd-arch=40freebsd.org?=" <freebsd-arch@freebsd.org> Subject: RE: Partial cacheline flush problems on ARM and MIPS Message-ID: <zarafa.503b0e81.5c36.1a2f71091ebf9bd2@eric2.bitfrost> In-Reply-To: <6D83AF9D-577B-4C83-84B7-C4E3B32695FC@bsdimp.com> References: <6D83AF9D-577B-4C83-84B7-C4E3B32695FC@bsdimp.com>
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Hi, Correct. > We also need some rules about working with buffers obtained from > bus_dmamem_alloc() and external buffers passed to bus_dmamap_load(). I > think the rule should be that a buffer obtained from bus_dmamem_alloc(), > or more formally any region of memory mapped by a bus_dmamap_load(), is > a single logical object which can only be accessed by one entity at a > time. That means that there cannot be two concurrent DMA operations > happening in different regions of the same buffer, nor can DMA and CPU > access be happening concurrently even if in different parts of the > buffer. Is this something which we can fix using a simple __align(USB_DMA_ALIGN) on elements in C-structures which are allowed to be DMA loaded. Also: Why is busdma not complaining when loading a non-valid buffer pointer? --HPS
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