From: gavinli@xxxxxxxxxxxxxx > Sent: 01 August 2019 23:02 > > On architectures that are not (or are optionally) DMA coherent, > dma_alloc_coherent() returns an address into the vmalloc space, > and calling virt_to_phys() on this address returns an unusable > physical address. So? what is the code trying to use the return value of virt_to_phys() for? The 'cpu physical address' isn't (usually) a very interesting number. The value you normally want is the address the hardware should use in order to access the memory - this isn't (in general) the same value. (It might be different for different devices.) ISTR that dma_alloc_coherent() returns this value to the caller. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
