dma-direct: provide generic support for uncached kernel segments

A few architectures support uncached kernel segments.  In that case we get
an uncached mapping for a given physica address by using an offset in the
uncached segement.  Implement support for this scheme in the generic
dma-direct code instead of duplicating it in arch hooks.

Signed-off-by: Christoph Hellwig <hch@lst.de>

1 files changed, 15 insertions, 2 deletions

diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c
index 0816c1e8b05a..b67f0aa08aa3 100644
--- a/kernel/dma/direct.c
+++ b/kernel/dma/direct.c
@@ -158,6 +158,13 @@ void *dma_direct_alloc_pages(struct device *dev, size_t size,
                 *dma_handle = phys_to_dma(dev, page_to_phys(page));
         }
         memset(ret, 0, size);
+
+        if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+            !dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_NON_CONSISTENT)) {
+                arch_dma_prep_coherent(page, size);
+                ret = uncached_kernel_address(ret);
+        }
+
         return ret;
 }
 
@@ -173,13 +180,18 @@ void dma_direct_free_pages(struct device *dev, size_t size, void *cpu_addr,
 
         if (force_dma_unencrypted())
                 set_memory_encrypted((unsigned long)cpu_addr, 1 << page_order);
+
+        if (IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+            !dev_is_dma_coherent(dev) && !(attrs & DMA_ATTR_NON_CONSISTENT))
+                cpu_addr = cached_kernel_address(cpu_addr);
         __dma_direct_free_pages(dev, size, virt_to_page(cpu_addr));
 }
 
 void *dma_direct_alloc(struct device *dev, size_t size,
                 dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs)
 {
-        if (!dev_is_dma_coherent(dev))
+        if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+            !dev_is_dma_coherent(dev))
                 return arch_dma_alloc(dev, size, dma_handle, gfp, attrs);
         return dma_direct_alloc_pages(dev, size, dma_handle, gfp, attrs);
 }
@@ -187,7 +199,8 @@ void *dma_direct_alloc(struct device *dev, size_t size,
 void dma_direct_free(struct device *dev, size_t size,
                 void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs)
 {
-        if (!dev_is_dma_coherent(dev))
+        if (!IS_ENABLED(CONFIG_ARCH_HAS_UNCACHED_SEGMENT) &&
+            !dev_is_dma_coherent(dev))
                 arch_dma_free(dev, size, cpu_addr, dma_addr, attrs);
         else
                 dma_direct_free_pages(dev, size, cpu_addr, dma_addr, attrs);