On 8/8/2014 3:45 PM, Andrew Morton wrote:
> On Fri, 8 Aug 2014 13:23:15 -0700 Laura Abbott <lauraa@xxxxxxxxxxxxxx> wrote:
>
>>
>> For architectures without coherent DMA, memory for DMA may
>> need to be remapped with coherent attributes. Factor out
>> the the remapping code from arm and put it in a
>> common location to reduce code duplication.
>>
>> As part of this, the arm APIs are now migrated away from
>> ioremap_page_range to the common APIs which use map_vm_area for remapping.
>> This should be an equivalent change and using map_vm_area is more
>> correct as ioremap_page_range is intended to bring in io addresses
>> into the cpu space and not regular kernel managed memory.
>>
>> ...
>>
>> @@ -267,3 +269,68 @@ int dma_common_mmap(struct device *dev, struct vm_area_struct *vma,
>> return ret;
>> }
>> EXPORT_SYMBOL(dma_common_mmap);
>> +
>> +/*
>> + * remaps an allocated contiguous region into another vm_area.
>> + * Cannot be used in non-sleeping contexts
>> + */
>> +
>> +void *dma_common_contiguous_remap(struct page *page, size_t size,
>> + unsigned long vm_flags,
>> + pgprot_t prot, const void *caller)
>> +{
>> + int i;
>> + struct page **pages;
>> + void *ptr;
>> +
>> + pages = kmalloc(sizeof(struct page *) << get_order(size), GFP_KERNEL);
>> + if (!pages)
>> + return NULL;
>> +
>> + for (i = 0; i < (size >> PAGE_SHIFT); i++)
>> + pages[i] = page + i;
>
> Assumes a single mem_map[] array. That's not the case for sparsemem
> (at least).
>
>
Good point. I guess the best option is to increment via pfn and call
pfn_to_page. Either that or go back to slightly abusing
ioremap_page_range to remap normal memory.
Thanks,
Laura
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