On 27/07/18 01:22, Grygorii Strashko wrote: [...]
the result of this change is pretty strange as for me :( Resulted code:/* * If @dev is expected to be DMA-capable then the bus code that created * it should have initialised its dma_mask pointer by this point. For * now, we'll continue the legacy behaviour of coercing it to the * coherent mask if not, but we'll no longer do so quietly. */ if (!dev->dma_mask) { dev_warn(dev, "DMA mask not set\n"); dev->dma_mask = &dev->coherent_dma_mask; ^this will always produce warning in case of platform-bus or if there are no bus driver. even if DT contains correct definition of dma-range } if (!size && dev->coherent_dma_mask) ^ coherent_dma_mask is zero, so size will not be calculatedpls, ignore this particular commentsize = max(dev->coherent_dma_mask, dev->coherent_dma_mask + 1); else if (!size) size = 1ULL << 32; dev->dma_pfn_offset = offset; /* * Limit coherent and dma mask based on size and default mask * set by the driver. */ mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1); dev->bus_dma_mask = mask; dev->coherent_dma_mask &= mask; ^^ if nobody set coherent_dma_mask before it will stay null forever unless drivers will overwrite it. Again even if DT has correct definition for dma-range.
That is intentional. Consider a 32-bit device on a bus with an upstream DMA range of 40 bits (which could easily happen with e.g. PCI). If the firmware code gives that device 40-bit DMA masks and the driver doesn't change them, then DMA is not going to work correctly. Therefore the firmware code cannot safely make {coherent_}dma_mask larger than the default value passed in, and if the default is 0 then that should be fixed in whatever code created the device, not worked around later.
Robin.
*dev->dma_mask &= mask; coherent = of_dma_is_coherent(np); dev_dbg(dev, "device is%sdma coherent\n", coherent ? " " : " not ");FYI, with below diff i can boot at least: diff --git a/drivers/of/device.c b/drivers/of/device.c index 5957cd4..f7dc121 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -150,8 +150,8 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma) */ mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1); dev->bus_dma_mask = mask; - dev->coherent_dma_mask &= mask; - *dev->dma_mask &= mask; + dev->coherent_dma_mask = mask; + *dev->dma_mask = mask;coherent = of_dma_is_coherent(np);dev_dbg(dev, "device is%sdma coherent\n",
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