Some platforms might define the same memory region to be suitable for used by a kernel supporting CONFIG_DMA_RESTRICTED_POOL while maintaining compatibility with older kernels that do not support that. This is achieved by declaring the node this way;
cma@40000000 { compatible = "restricted-dma-pool", "shared-dma-pool"; reusable; ... }; A newer kernel would leverage the 'restricted-dma-pool' compatible string for that reserved region, while an older kernel would use the 'shared-dma-pool' compatibility string. Due to the link ordering between files under kernel/dma/ however, contiguous.c would try to claim the region and we would never get a chance for swiotlb.c to claim that reserved memory region. To that extent, update kernel/dma/contiguous.c in order to check specifically for the 'restricted-dma-pool' compatibility string when CONFIG_DMA_RESTRICTED_POOL is enabled and give up that region such that kernel/dma/swiotlb.c has a chance to claim it. Similarly, kernel/dma/swiotlb.c is updated to remove the check for the 'reusable' property because that check is not useful. When a region is defined with a compatible string set to 'restricted-dma-pool', no code under kernel/dma/{contiguous,coherent}.c will match that region since there is no 'shared-dma-pool' compatible string. If a region is defined with a compatible string set as above with both 'restricted-dma-pool" *and* 'shared-dma-pool' however, checking for 'reusable' will prevent kernel/dma/swiotlb.c from claiming the region while it is still perfectly suitable since contiguous.c gave it up. Signed-off-by: Florian Fainelli <f.faine...@gmail.com> --- kernel/dma/contiguous.c | 7 +++++++ kernel/dma/swiotlb.c | 3 +-- 2 files changed, 8 insertions(+), 2 deletions(-) diff --git a/kernel/dma/contiguous.c b/kernel/dma/contiguous.c index 3d63d91cba5c..3c418af6d306 100644 --- a/kernel/dma/contiguous.c +++ b/kernel/dma/contiguous.c @@ -416,6 +416,13 @@ static int __init rmem_cma_setup(struct reserved_mem *rmem) of_get_flat_dt_prop(node, "no-map", NULL)) return -EINVAL; +#ifdef CONFIG_DMA_RESTRICTED_POOL + if (of_flat_dt_is_compatible(node, "restricted-dma-pool")) { + pr_warn("Giving up %pa for restricted DMA pool\n", &rmem->base); + return -ENOENT; + } +#endif + if ((rmem->base & mask) || (rmem->size & mask)) { pr_err("Reserved memory: incorrect alignment of CMA region\n"); return -EINVAL; diff --git a/kernel/dma/swiotlb.c b/kernel/dma/swiotlb.c index f1e7ea160b43..9d6e4ae74d04 100644 --- a/kernel/dma/swiotlb.c +++ b/kernel/dma/swiotlb.c @@ -883,8 +883,7 @@ static int __init rmem_swiotlb_setup(struct reserved_mem *rmem) { unsigned long node = rmem->fdt_node; - if (of_get_flat_dt_prop(node, "reusable", NULL) || - of_get_flat_dt_prop(node, "linux,cma-default", NULL) || + if (of_get_flat_dt_prop(node, "linux,cma-default", NULL) || of_get_flat_dt_prop(node, "linux,dma-default", NULL) || of_get_flat_dt_prop(node, "no-map", NULL)) return -EINVAL; -- 2.25.1 _______________________________________________ iommu mailing list iommu@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/iommu