Re: [Linaro-mm-sig] [PATCHv2 1/2] ARM: dma-mapping: add support for CMA regions placed in highmem zone

On Mon, Feb 04 2013, Russell King - ARM Linux wrote:

On Mon, Feb 04, 2013 at 02:51:52PM +0100, Michal Nazarewicz wrote:

...

On Mon, Feb 04 2013, Marek Szyprowski wrote:

...

@@ -186,13 +186,24 @@ static u64 get_coherent_dma_mask(struct device *dev) static void __dma_clear_buffer(struct page *page, size_t size) {

• void *ptr; /*
  • Ensure that the allocated pages are zeroed, and that any data
  • lurking in the kernel direct-mapped region is invalidated.
  */
• ptr = page_address(page);
• if (ptr) {

• if (PageHighMem(page)) {

• phys_addr_t base = __pfn_to_phys(page_to_pfn(page));
  

• phys_addr_t end = base + size;
  

• while (size > 0) {
  

• 	void *ptr = kmap_atomic(page);
  

• 	memset(ptr, 0, PAGE_SIZE);
  

• 	dmac_flush_range(ptr, ptr + PAGE_SIZE);
  

• 	kunmap_atomic(ptr);
  

• 	page++;
  

• 	size -= PAGE_SIZE;
  

• }
  

• outer_flush_range(base, end);
  

• } else {

• void *ptr = page_address(page);
  

There used to be a “if (ptr)” check which is now missing. Why is that?

Because lowmem pages always have an address.

Perhaps it should use lowmem_page_address() then?