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Commit 6090912c authored by Benjamin Herrenschmidt's avatar Benjamin Herrenschmidt
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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: default avatarBenjamin Herrenschmidt <benh@kernel.crashing.org>
parent 15d260b3

arch/powerpc/include/asm/dma-mapping.h

+6 −0
Original line number Diff line number Diff line
@@ -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(unsigned long cpu_addr);



#else /* ! CONFIG_NOT_COHERENT_CACHE */

/*
@@ -198,6 +199,11 @@ 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)

{

arch/powerpc/kernel/dma.c

+18 −0
Original line number Diff line number Diff line
@@ -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((unsigned long)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);

}

EXPORT_SYMBOL_GPL(dma_mmap_coherent);

arch/powerpc/mm/dma-noncoherent.c

+20 −0
Original line number Diff line number Diff line
@@ -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(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);

}