This is used by Alsa to mmap buffers allocated with dma_alloc_coherent()
into userspace. We need a special variant to handle machines with
non-coherent DMAs as those buffers have "special" virt addresses and
require non-cachable mappings
Signed-off-by: Benjamin Herrenschmidt <b...@kernel.crashing.org>
---
Dunno if anybody with CONFIG_NOT_COHERENT_CACHE has some audio device
that uses dma buffers (ie not usb-audio) and wants to try that out...
should fix a long standing problem.
arch/powerpc/include/asm/dma-mapping.h | 7 +++++++
arch/powerpc/kernel/dma.c | 18 ++++++++++++++++++
arch/powerpc/mm/dma-noncoherent.c | 20 ++++++++++++++++++++
3 files changed, 45 insertions(+), 0 deletions(-)
diff --git a/arch/powerpc/include/asm/dma-mapping.h
b/arch/powerpc/include/asm/dma-mapping.h
index 6d2416a..41e0eb7 100644
--- a/arch/powerpc/include/asm/dma-mapping.h
+++ b/arch/powerpc/include/asm/dma-mapping.h
@@ -42,6 +42,7 @@ extern void __dma_free_coherent(size_t size, void *vaddr);
extern void __dma_sync(void *vaddr, size_t size, int direction);
extern void __dma_sync_page(struct page *page, unsigned long offset,
size_t size, int direction);
+extern unsigned long __dma_get_coherent_pfn(void *cpu_addr);
#else /* ! CONFIG_NOT_COHERENT_CACHE */
/*
@@ -52,6 +53,7 @@ extern void __dma_sync_page(struct page *page, unsigned long
offset,
#define __dma_free_coherent(size, addr) ((void)0)
#define __dma_sync(addr, size, rw) ((void)0)
#define __dma_sync_page(pg, off, sz, rw) ((void)0)
+#define __dma_get_coherent_pfn(cpu_addr) (0)
#endif /* ! CONFIG_NOT_COHERENT_CACHE */
@@ -198,6 +200,11 @@ static inline phys_addr_t dma_to_phys(struct device *dev,
dma_addr_t daddr)
#define dma_alloc_noncoherent(d, s, h, f) dma_alloc_coherent(d, s, h, f)
#define dma_free_noncoherent(d, s, v, h) dma_free_coherent(d, s, v, h)
+extern int dma_mmap_coherent(struct device *, struct vm_area_struct *,
+ void *, dma_addr_t, size_t);
+#define ARCH_HAS_DMA_MMAP_COHERENT
+
+
static inline void dma_cache_sync(struct device *dev, void *vaddr, size_t size,
enum dma_data_direction direction)
{
diff --git a/arch/powerpc/kernel/dma.c b/arch/powerpc/kernel/dma.c
index cf02cad..0f52235 100644
--- a/arch/powerpc/kernel/dma.c
+++ b/arch/powerpc/kernel/dma.c
@@ -179,3 +179,21 @@ static int __init dma_init(void)
return 0;
}
fs_initcall(dma_init);
+
+int dma_mmap_coherent(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t handle, size_t size)
+{
+ unsigned long pfn;
+
+#ifdef CONFIG_NOT_COHERENT_CACHE
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+ pfn = __dma_get_coherent_pfn(cpu_addr);
+#else
+ pfn = page_to_pfn(virt_to_page(cpu_addr));
+#endif
+ return remap_pfn_range(vma, vma->vm_start,
+ pfn + vma->vm_pgoff,
+ vma->vm_end - vma->vm_start,
+ vma->vm_page_prot);
+}
+
diff --git a/arch/powerpc/mm/dma-noncoherent.c
b/arch/powerpc/mm/dma-noncoherent.c
index 757c0be..174b10a 100644
--- a/arch/powerpc/mm/dma-noncoherent.c
+++ b/arch/powerpc/mm/dma-noncoherent.c
@@ -399,3 +399,23 @@ void __dma_sync_page(struct page *page, unsigned long
offset,
#endif
}
EXPORT_SYMBOL(__dma_sync_page);
+
+/*
+ * Return the PFN for a given cpu virtual address returned by
+ * __dma_alloc_coherent. This is used by dma_mmap_coherent()
+ */
+unsigned long __dma_get_coherent_pfn(void *cpu_addr)
+{
+ /* This should always be populated, so we don't test every
+ * level. If that fails, we'll have a nice crash which
+ * will be as good as a BUG_ON()
+ */
+ pgd_t *pgd = pgd_offset_k(cpu_addr);
+ pud_t *pud = pud_offset(pgd, cpu_addr);
+ pmd_t *pmd = pmd_offset(pud, cpu_addr);
+ pte_t *ptep = pte_offset_kernel(pmd, cpu_addr);
+
+ if (pte_none(*ptep) || !pte_present(*ptep))
+ return 0;
+ return pte_pfn(*ptep);
+}
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