[PATCH 1/2] arm64: dma_mapping: allow PCI host driver to limit DMA mask
From: nikita.yoush@cogentembedded.com (Nikita Yushchenko)
Date: 2017-01-04 06:31:38
Also in:
linux-pci, linux-renesas-soc, lkml
commit 9a57d58d116800a535510053136c6dd7a9c26e25
Author: Arnd Bergmann [off-list ref]
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 [off-list ref]Unfortunately this is far incomplete
quoted hunk ↗ jump to hunk
@@ -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.