Hi Frank, On 4/6/2017 12:31 PM, Frank Rowand wrote:
On 04/04/17 03:18, Sricharan R wrote:Size of the dma-range is calculated as coherent_dma_mask + 1 and passed to arch_setup_dma_ops further. It overflows when the coherent_dma_mask is set for full 64 bits 0xFFFFFFFFFFFFFFFF, resulting in size getting passed as 0 wrongly. Fix this by passsing in max(mask, mask + 1). Note that in this case when the mask is set to full 64bits, we will be passing the mask itself to arch_setup_dma_ops instead of the size. The real fix for this should be to make arch_setup_dma_ops receive the mask and handle it, to be done in the future. Signed-off-by: Sricharan R <sricharan@xxxxxxxxxxxxxx> --- drivers/of/device.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/drivers/of/device.c b/drivers/of/device.c index c17c19d..c2ae6bb 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -107,7 +107,7 @@ void of_dma_configure(struct device *dev, struct device_node *np) ret = of_dma_get_range(np, &dma_addr, &paddr, &size); if (ret < 0) { dma_addr = offset = 0; - size = dev->coherent_dma_mask + 1; + size = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1); } else { offset = PFN_DOWN(paddr - dma_addr); dev_dbg(dev, "dma_pfn_offset(%#08lx)\n", offset);NACK. Passing an invalid size to arch_setup_dma_ops() is only part of the problem. size is also used in of_dma_configure() before calling arch_setup_dma_ops(): dev->coherent_dma_mask = min(dev->coherent_dma_mask, DMA_BIT_MASK(ilog2(dma_addr + size))); *dev->dma_mask = min((*dev->dma_mask), DMA_BIT_MASK(ilog2(dma_addr + size))); which would be incorrect for size == 0xffffffffffffffffULL when dma_addr != 0. So the proposed fix really is not papering over the base problem very well.
Ok, but with your fix for of_dma_get_range and the above fix, dma_addr will be '0' when size = 0xffffffffffffffffULL, but DMA_BIT_MASK(ilog2(dma_addr + size)) would be wrong though, making coherent_dma_mask to be smaller 0x7fffffffffffffffULL. Regards, Sricharan
I agree that the proper solution involves passing a mask instead of a size to arch_setup_dma_ops().
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