powerpc: Implement dma_mmap_coherent()
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 <benh@kernel.crashing.org>
diff --git a/arch/powerpc/mm/dma-noncoherent.c b/arch/powerpc/mm/dma-noncoherent.c
index 757c0be..b42f76c 100644
--- a/arch/powerpc/mm/dma-noncoherent.c
+++ b/arch/powerpc/mm/dma-noncoherent.c
@@ -399,3 +399,23 @@
#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(unsigned long 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);
+}