From: Hiroshi DOYU hdoyu@nvidia.com Subject: Re: [PATCHv7 9/9] ARM: dma-mapping: add support for IOMMU mapper Date: Wed, 07 Mar 2012 08:09:52 +0200 (EET) Message-ID: 20120307.080952.2152478004740487196.hdoyu@nvidia.com
From: Krishna Reddy vdumpa@nvidia.com Subject: RE: [PATCHv7 9/9] ARM: dma-mapping: add support for IOMMU mapper Date: Tue, 6 Mar 2012 23:48:42 +0100 Message-ID: 401E54CE964CD94BAE1EB4A729C7087E37970113FE@HQMAIL04.nvidia.com
+struct dma_iommu_mapping * +arm_iommu_create_mapping(struct bus_type *bus, dma_addr_t base, size_t size,
int order)+{
unsigned int count = (size >> PAGE_SHIFT) - order;unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long);The count calculation doesn't seem correct. "order" is log2 number and size >> PAGE_SHIFT is number of pages.
If size is passed as 64*4096(256KB) and order is 6(allocation granularity is 2^6 pages=256KB), just 1 bit is enough to manage allocations. So it should be 4 bytes or one long.
Good catch!
But the calculation gives count = 64 - 6 = 58 and Bitmap_size gets set to (58/(4*8)) * 4 = 8 bytes, which is incorrect.
"order" isn't the order of size passed, which is minimal *page* allocation order which client decides whatever, just in case.
It should be as follows. unsigned int count = 1 << get_order(size) - order;
To be precise, as below?
unsigned int count = 1 << (get_order(size) - order);
unsigned int bitmap_size = BITS_TO_LONGS(count) * sizeof(long) * BITS_PER_BYTE;
-KR
--nvpublic