The generic implementation of dma_map_ops.mmap(), dma_common_mmap(),
is not correct for non-coherent devices. It expects to be passed a
virtual address previously returned by dma_alloc_coherent(), which for
a non-coherent device will return a KSEG1 address. It then attempts to
convert that virtual address to a physical address using virt_to_page()
which will yield an incorrect address.
Also, dma_common_mmap() does not handle the DMA_ATTR_WRITE_COMBINE
attribute, and therefore dma_mmap_writecombine() will not actually set
the appropriate pgprot_t flags for write combining.
This patch adds an implementation of dma_map_ops.mmap() that correctly
handles KSEG1 addresses, and enables write combining when requested.
Signed-off-by: Alex Smith <alex.smith@xxxxxxxxxx>
Cc: Sadegh Abbasi <Sadegh.Abbasi@xxxxxxxxxx>
Cc: linux-mips@xxxxxxxxxxxxxx
---
Ralf: Could you replace the old patch "MIPS: Add implementation of
dma_map_ops.mmap() that handles write combining" in mips-for-linux-next
with this patch, which fixes a problem pointed out to me that exists
in both dma_common_mmap() and the original version of the patch I sent.
---
arch/mips/mm/dma-default.c | 35 +++++++++++++++++++++++++++++++++++
1 file changed, 35 insertions(+)
diff --git a/arch/mips/mm/dma-default.c b/arch/mips/mm/dma-default.c
index eeaf0245c3b1..8f23cf08f4ba 100644
--- a/arch/mips/mm/dma-default.c
+++ b/arch/mips/mm/dma-default.c
@@ -194,6 +194,40 @@ static void mips_dma_free_coherent(struct device *dev, size_t size, void *vaddr,
__free_pages(page, get_order(size));
}
+static int mips_dma_mmap(struct device *dev, struct vm_area_struct *vma,
+ void *cpu_addr, dma_addr_t dma_addr, size_t size,
+ struct dma_attrs *attrs)
+{
+ unsigned long user_count = (vma->vm_end - vma->vm_start) >> PAGE_SHIFT;
+ unsigned long count = PAGE_ALIGN(size) >> PAGE_SHIFT;
+ unsigned long addr = (unsigned long)cpu_addr;
+ unsigned long off = vma->vm_pgoff;
+ unsigned long pfn;
+ int ret = -ENXIO;
+
+ if (!plat_device_is_coherent(dev) && !hw_coherentio)
+ addr = CAC_ADDR(addr);
+
+ pfn = page_to_pfn(virt_to_page((void *)addr));
+
+ if (dma_get_attr(DMA_ATTR_WRITE_COMBINE, attrs))
+ vma->vm_page_prot = pgprot_writecombine(vma->vm_page_prot);
+ else
+ vma->vm_page_prot = pgprot_noncached(vma->vm_page_prot);
+
+ if (dma_mmap_from_coherent(dev, vma, cpu_addr, size, &ret))
+ return ret;
+
+ if (off < count && user_count <= (count - off)) {
+ ret = remap_pfn_range(vma, vma->vm_start,
+ pfn + off,
+ user_count << PAGE_SHIFT,
+ vma->vm_page_prot);
+ }
+
+ return ret;
+}
+
static inline void __dma_sync_virtual(void *addr, size_t size,
enum dma_data_direction direction)
{
@@ -380,6 +414,7 @@ EXPORT_SYMBOL(dma_cache_sync);
static struct dma_map_ops mips_default_dma_map_ops = {
.alloc = mips_dma_alloc_coherent,
.free = mips_dma_free_coherent,
+ .mmap = mips_dma_mmap,
.map_page = mips_dma_map_page,
.unmap_page = mips_dma_unmap_page,
.map_sg = mips_dma_map_sg,
--
2.5.0
