On Fri, Jan 30, 2015 at 06:06:27PM +0000, Murali Karicheri wrote:
> On 01/28/2015 12:30 PM, Catalin Marinas wrote:
> > I think we can remove this check altogether (we leaved without it for a
> > while) but we need to add 1 when calculating the mask:
> >
> > dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
> > DMA_BIT_MASK(ilog2(size + 1)));
> >
> For Keystone, the dma_addr is to be taken care as well to determine the
> mask. The above will not work.
This was discussed before (not on this thread) and dma_addr should not
affect the mask, it only affects the pfn offset.
> Based on the discussion so far, this is the function I have come up with
> incorporating the suggestions. Please review this and see if I have
> missed out any. This works fine on Keystone.
>
> void of_dma_configure(struct device *dev, struct device_node *np)
> {
> u64 dma_addr = 0, paddr, size;
> int ret;
> bool coherent;
> unsigned long offset = 0;
> struct iommu_ops *iommu;
>
> /*
> * Set default size to cover the 32-bit. Drivers are expected to setup
> * the correct size and dma_mask.
> */
> size = 1ULL << 32;
>
> ret = of_dma_get_range(np, &dma_addr, &paddr, &size);
> if (!ret) {
> offset = PFN_DOWN(paddr - dma_addr);
> if (!size) {
> dev_err(dev, "Invalid size (%llx)\n",
> size);
> return;
> }
> if (size & 1) {
> size = size + 1;
> dev_warn(dev, "Incorrect usage of size (%llx)\n",
> size);
> }
> dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);
> }
> dev->dma_pfn_offset = offset;
>
> /*
> * Coherent DMA masks larger than 32-bit must be explicitly set by the
> * driver.
> */
> dev->coherent_dma_mask = min(DMA_BIT_MASK(32),
> DMA_BIT_MASK(ilog2(dma_addr + size)));
That's not correct, coherent_dma_mask should still be calculated solely
based on size, not dma_addr.
Functions like swiotlb_dma_supported() use phys_to_dma() which on ARM
(32-bit) subtracts the dma_pfn_offset, so the mask based on size works
fine.
In the arm64 tree, we haven't taken dma_pfn_offset into account for
phys_to_dma() yet but if needed for a SoC, we'll add it.
--
Catalin
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