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Date: Sun, 20 Jul 2008 22:11:32 +0200 From: Stefan Richter <stefanr@...6.in-berlin.de> To: Arjan van de Ven <arjan@...radead.org> CC: linuxppc-dev@...abs.org, linux-kernel@...r.kernel.org Subject: Re: dma_alloc_coherent() on PPC32: physical addresses above 2G possible? Arjan van de Ven wrote: > On Sun, 20 Jul 2008 21:25:51 +0200 > Stefan Richter <stefanr@...6.in-berlin.de> wrote: >> if (dev->needs_dma_mask_workaround) >> pci_set_consistent_dma_mask(pdev, DMA_31BIT_MASK); >> allocate_something_special; >> if (dev->needs_dma_mask_workaround) >> pci_set_consistent_dma_mask(pdev, DMA_32BIT_MASK); ... > something like this. > But realistically, how many consistent/coherent allocations do you have? > some ring buffers and other one time stuff surely... but not after that? It's for DMA programs (i.e. lists of descriptors), not for the data DMA buffers themselves. FireWire controllers have several DMA contexts for isochronous and asynchronous reception and transmission, and some others. Only context programs for isochronous reception need the workaround. We are dynamically appending new descriptors during runtime. I.e. the affected allocations happen during setup of the DMA context and sometimes while the DMA context is active. Particularly, in drivers/firewire/fw-ohci.c: ohci_allocate_iso_context context_init context_add_buffer <-- and ohci_queue_iso ohci_queue_iso_receive_dualbuffer context_get_descriptors context_add_buffer <-- The other unaffected context types use context_add_buffer too. -- Stefan Richter -=====-==--- -=== =-=-- http://arcgraph.de/sr/ -- 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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