Re: [PATCH 3/3] MIPS: handle write_combine in pci_mmap_page_range

[yanh <yanh@lemote.com>]

在 2009-05-08五的 14:30 +0800，Zhang Le写道：
> Signed-off-by: Zhang Le <r0bertz@gentoo.org>
> ---
>  arch/mips/pci/pci.c |    8 ++++++--
>  1 files changed, 6 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/mips/pci/pci.c b/arch/mips/pci/pci.c
> index b0eb9e7..4ca53ef 100644
> --- a/arch/mips/pci/pci.c
> +++ b/arch/mips/pci/pci.c
> @@ -346,10 +346,14 @@ int pci_mmap_page_range(struct pci_dev *dev, struct vm_area_struct *vma,
>  		return -EINVAL;
>  
>  	/*
> -	 * Ignore write-combine; for now only return uncached mappings.
> +	 * For write-combine, return uncached accelerated mappings if CPU
> +	 * supports; otherwise, return uncached mappings.
>  	 */
>  	prot = pgprot_val(vma->vm_page_prot);
> -	prot = (prot & ~_CACHE_MASK) | _CACHE_UNCACHED;
> +	if (write_combine && cpu_has_uncached_accelerated)
> +		prot = (prot & ~_CACHE_MASK) | _CACHE_UNCACHED_ACCELERATED;
> +	else
> +		prot = (prot & ~_CACHE_MASK) | _CACHE_UNCACHED;
>  	vma->vm_page_prot = __pgprot(prot);
This should be definietely wrong for MMIOs.
uncache accelleration should only be enabled for addresses which have no
side effect when doing write combine such as video memory.
>  
>  	return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff,