Resubmitting this patch from a few months ago now that the "x86/PAT:
... map pfn RAM range req uncached-minus" warning mentioned earlier
seems to have been fixed.
On Wed, May 6, 2020 at 5:57 PM <gavinli@xxxxxxxxxxxxxx> wrote:
>
> From: Gavin Li <gavinli@xxxxxxxxxxxxxx>
>
> 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.
> ---
> 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 6833c918abce..9d0043dd8e64 100644
> --- a/drivers/usb/core/devio.c
> +++ b/drivers/usb/core/devio.c
> @@ -250,11 +250,10 @@ 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;
> --
> 2.26.2
>
