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
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