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Date: Wed, 17 Jun 2009 03:13:07 +0200 From: Leon Woestenberg <leon.woestenberg@...il.com> To: Benjamin Herrenschmidt <benh@...nel.crashing.org> Cc: FUJITA Tomonori <fujita.tomonori@....ntt.co.jp>, arnd@...db.de, scottwood@...escale.com, chris.pringle@...el.com, linuxppc-dev@...ts.ozlabs.org, linux-kernel@...r.kernel.org Subject: Re: PowerPC PCI DMA issues (prefetch/coherency?) Hello Benjamin, On Wed, Jun 17, 2009 at 3:08 AM, Benjamin Herrenschmidt<benh@...nel.crashing.org> wrote: > On Wed, 2009-06-17 at 02:56 +0200, Leon Woestenberg wrote: >> I use pci_map_sg(), have the device perform either DMA master reads or >> writes to the bus address using PCIe. >> After that, I use pci_unmap_sg(). >> >> My assumption is that pci_unmap_sg() either makes the cache coherent >> or invalidated and thus I do not need to take further actions. >> This is on a MPC83xx or 85xx system. >> >> Is this assumption correct? > > It is, as far as I understand things :-) Those APIs are fun. > > You should only need the explicit sync calls if you are going to peek or > poke at the DMA mapped memory before you unmap it. > Thanks, then at least I understand things in the corr^H^H^H^Hsame way :-) And btw, I hadn't seen any data mismatch yet. Regards, -- Leon 'likewise' Woestenberg -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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