From: Hiroshi DOYU <[email protected]> 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: <[email protected]>
> From: Krishna Reddy <[email protected]> > Subject: RE: [PATCHv7 9/9] ARM: dma-mapping: add support for IOMMU mapper > Date: Tue, 6 Mar 2012 23:48:42 +0100 > Message-ID: <[email protected]> > > > > > +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 > > > > _______________________________________________ iommu mailing list [email protected] https://lists.linuxfoundation.org/mailman/listinfo/iommu
