For dma_alloc_coherent() you don't need writel/readl because
it's just a plain old void *. Linux tries very hard to make a
distinction between io memory (void __iomem *) and memory
(void *) so that drivers are portable to architectures that
don't have a way to access registers via pointer dereferences.
You can see http://lwn.net/Articles/102232/ and the Linus rant
http://lwn.net/Articles/102240/ here for more details behind
the motivation.
msm: kgsl: Allocate physical pages instead of using vmalloc
Replace vmalloc allocation with physical page allocation. For most
allocations we do not need a kernel virual address. vmalloc uses up
the kernel virtual address space. By replacing vmalloc with physical
page alloction and mapping that allocation to kernel space only
when it is required prevents the kgsl driver from using unnecessary
vmalloc virtual space.
