On 16:54 Fri 08 May , yanh wrote: > > 在 2009-05-08五的 14:30 +0800，Zhang Le写道： > > Signed-off-by: Zhang Le <r0bertz@xxxxxxxxxx> > > --- > > 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. Actually, currently write_combine is true only for prefetchable pci memory: http://lxr.linux.no/linux+v2.6.29/drivers/pci/pci-sysfs.c#L711 And currently on fuloong 2f box, there is only one prefetchable pci memory region, which just belongs to video card: zhangle@2f /sys/devices/pci0000:00 (n32) $ find -name "*wc" -exec ls -l {} \; -rw------- 1 root root 256M 2009-05-08 03:25 ./0000:00:08.0/resource0_wc So, are we talking about the same thing? Also, I have observed that this region is larger than the actual video ram size 32M. However, libpciaccess only mapped 32M into X's address space: zhangle@2f ~ (n32) $ sudo cat /proc/$(pidof X)/maps | grep wc$ 2b354000-2d354000 rw-s 50000000 00:00 1882 /sys/devices/pci0000:00/0000:00:08.0/resource0_wc So, I guess this should be just ok, right? Any other risks? > > > > return remap_pfn_range(vma, vma->vm_start, vma->vm_pgoff, > -- Zhang, Le Gentoo/Loongson Developer http://zhangle.is-a-geek.org 0260 C902 B8F8 6506 6586 2B90 BC51 C808 1E4E 2973
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