From ee7b1f31200d9f3cc45e1bd22e962bd6b1d4d611 Mon Sep 17 00:00:00 2001 From: Robin Murphy Date: Fri, 11 Aug 2017 17:29:56 +0100 Subject: [PATCH] of: fix DMA mask generation MIME-Version: 1.0 Content-Type: text/plain; charset=utf8 Content-Transfer-Encoding: 8bit Historically, DMA masks have suffered some ambiguity between whether they represent the range of physical memory a device can access, or the address bits a device is capable of driving, particularly since on many platforms the two are equivalent. Whilst there are some stragglers left (dma_max_pfn(), I'm looking at you...), the majority of DMA code has been cleaned up to follow the latter definition, not least since it is the only one which makes sense once IOMMUs are involved. In this respect, of_dma_configure() has always done the wrong thing in how it generates initial masks based on "dma-ranges". Although rounding down did not affect the TI Keystone platform where dma_addr + size is already a power of two, in any other case it results in a mask which is at best unnecessarily constrained and at worst unusable. BCM2837 illustrates the problem nicely, where we have a DMA base of 3GB and a size of 1GB - 16MB, giving dma_addr + size = 0xff000000 and a resultant mask of 0x7fffffff, which is then insufficient to even cover the necessary offset, effectively making all DMA addresses out-of-range. This has been hidden until now (mostly because we don't yet prevent drivers from simply overwriting this initial mask later upon probe), but due to recent changes elsewhere now shows up as USB being broken on Raspberry Pi 3. Make it right by rounding up instead of down, such that the mask correctly correctly describes all possisble bits the device needs to emit. Fixes: 9a6d7298b083 ("of: Calculate device DMA masks based on DT dma-range size") Reported-by: Stefan Wahren Reported-by: Andreas Färber Reported-by: Hans Verkuil Signed-off-by: Robin Murphy Acked-by: Rob Herring Signed-off-by: Christoph Hellwig --- drivers/of/device.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) diff --git a/drivers/of/device.c b/drivers/of/device.c index 28c38c756f92..e0a28ea341fe 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -89,6 +89,7 @@ int of_dma_configure(struct device *dev, struct device_node *np) bool coherent; unsigned long offset; const struct iommu_ops *iommu; + u64 mask; /* * Set default coherent_dma_mask to 32 bit. Drivers are expected to @@ -134,10 +135,9 @@ int of_dma_configure(struct device *dev, struct device_node *np) * Limit coherent and dma mask based on size and default mask * set by the driver. */ - 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))); + mask = DMA_BIT_MASK(ilog2(dma_addr + size - 1) + 1); + dev->coherent_dma_mask &= mask; + *dev->dma_mask &= mask; coherent = of_dma_is_coherent(np); dev_dbg(dev, "device is%sdma coherent\n", -- 2.20.1