Messages in this thread | | | Subject | Re: [PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask | From | Nikita Yushchenko <> | Date | Wed, 4 Jan 2017 09:24:09 +0300 |
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> commit 9a57d58d116800a535510053136c6dd7a9c26e25 > Author: Arnd Bergmann <arnd@arndb.de> > Date: Tue Nov 17 14:06:55 2015 +0100 > > [EXPERIMENTAL] ARM64: check implement dma_set_mask > > Needs work for coherent mask > > Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Unfortunately this is far incomplete
> @@ -957,6 +983,18 @@ void arch_setup_dma_ops(struct device *dev, u64 dma_base, u64 size, > if (!dev->archdata.dma_ops) > dev->archdata.dma_ops = &swiotlb_dma_ops; > > + /* > + * we don't yet support buses that have a non-zero mapping. > + * Let's hope we won't need it > + */ > + WARN_ON(dma_base != 0); > + > + /* > + * Whatever the parent bus can set. A device must not set > + * a DMA mask larger than this. > + */ > + dev->archdata.parent_dma_mask = size; > +
... because size/mask passed here for PCI devices are meaningless.
For OF platforms, this is called via of_dma_configure(), that checks dma-ranges of node that is *parent* for host bridge. Host bridge currently does not control this at all.
In current device trees no dma-ranges is defined for nodes that are parents to pci host bridges. This will make of_dma_configure() to fall back to 32-bit size for all devices on all current platforms. Thus applying this patch will immediately break 64-bit dma masks on all hardware that supports it.
Also related: dma-ranges property used by several pci host bridges is *not* compatible with "legacy" dma-ranges parsed by of_get_dma_range() - former uses additional flags word at beginning.
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