On 02/02/2015 07:18 AM, Catalin Marinas wrote:

On Fri, Jan 30, 2015 at 06:06:27PM +0000, Murali Karicheri wrote:

quoted

On 01/28/2015 12:30 PM, Catalin Marinas wrote:

quoted

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.

quoted

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.

I need to hear Arnd's comment on this. I am seeing an issue without this 
change. Probably it needs a change else where. I will post the error I 
am getting to this list.

Murali

-- 
Murali Karicheri
Linux Kernel, Texas Instruments