[PATCH] usb: devio: fix mmap() on non-coherent DMA architectures

[gavinli@thegavinli.com]

From: Gavin Li <git@thegavinli.com>

On architectures that are not (or are optionally) DMA coherent,
dma_alloc_coherent() returns an address into the vmalloc space,
and calling virt_to_phys() on this address returns an unusable
physical address.

This patch replaces the raw remap_pfn_range() call with a call to
dmap_mmap_coherent(), which takes care of the differences between
coherent and non-coherent code paths.

Tested on an arm64 rk3399 board.

Signed-off-by: Gavin Li <git@thegavinli.com>
---
 drivers/usb/core/devio.c | 7 +++----
 1 file changed, 3 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/core/devio.c b/drivers/usb/core/devio.c
index a02448105527..76ec9aef3eff 100644
--- a/drivers/usb/core/devio.c
+++ b/drivers/usb/core/devio.c
@@ -241,11 +241,10 @@ static int usbdev_mmap(struct file *file, struct vm_area_struct *vma)
 	usbm->vma_use_count = 1;
 	INIT_LIST_HEAD(&usbm->memlist);
 
-	if (remap_pfn_range(vma, vma->vm_start,
-			virt_to_phys(usbm->mem) >> PAGE_SHIFT,
-			size, vma->vm_page_prot) < 0) {
+	ret = dma_mmap_coherent(ps->dev->bus->sysdev, vma, mem, dma_handle, size);
+	if (ret) {
 		dec_usb_memory_use_count(usbm, &usbm->vma_use_count);
-		return -EAGAIN;
+		return ret;
 	}
 
 	vma->vm_flags |= VM_IO;
-- 
2.22.0