Messages in this thread | | | Subject | Re: [PATCH 4/5] dma-direct: implement complete bus_dma_mask handling | From | Robin Murphy <> | Date | Thu, 27 Sep 2018 15:58:04 +0100 |
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On 20/09/18 19:52, Christoph Hellwig wrote: > Instead of rejecting devices with a too small bus_dma_mask we can handle > by taking the bus dma_mask into account for allocations and bounce > buffering decisions. > > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > include/linux/dma-direct.h | 3 ++- > kernel/dma/direct.c | 21 +++++++++++---------- > 2 files changed, 13 insertions(+), 11 deletions(-) > > diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h > index b79496d8c75b..fbca184ff5a0 100644 > --- a/include/linux/dma-direct.h > +++ b/include/linux/dma-direct.h > @@ -27,7 +27,8 @@ static inline bool dma_capable(struct device *dev, dma_addr_t addr, size_t size) > if (!dev->dma_mask) > return false; > > - return addr + size - 1 <= *dev->dma_mask; > + return addr + size - 1 <= > + min_not_zero(*dev->dma_mask, dev->bus_dma_mask); > } > #endif /* !CONFIG_ARCH_HAS_PHYS_TO_DMA */ > > diff --git a/kernel/dma/direct.c b/kernel/dma/direct.c > index 3c404e33d946..64466b7ef67b 100644 > --- a/kernel/dma/direct.c > +++ b/kernel/dma/direct.c > @@ -43,10 +43,11 @@ check_addr(struct device *dev, dma_addr_t dma_addr, size_t size, > return false; > } > > - if (*dev->dma_mask >= DMA_BIT_MASK(32)) { > + if (*dev->dma_mask >= DMA_BIT_MASK(32) || dev->bus_dma_mask) {
Hmm... say *dev->dma_mask is 31 bits and dev->bus_dma_mask is 40 bits due to a global DT property, we'll now scream where we didn't before even though the bus mask is almost certainly irrelevant - is that desirable?
> dev_err(dev, > - "%s: overflow %pad+%zu of device mask %llx\n", > - caller, &dma_addr, size, *dev->dma_mask); > + "%s: overflow %pad+%zu of device mask %llx bus mask %llx\n", > + caller, &dma_addr, size, > + *dev->dma_mask, dev->bus_dma_mask); > } > return false; > } > @@ -65,12 +66,18 @@ u64 dma_direct_get_required_mask(struct device *dev) > { > u64 max_dma = phys_to_dma_direct(dev, (max_pfn - 1) << PAGE_SHIFT); > > + if (dev->bus_dma_mask && dev->bus_dma_mask < max_dma) > + max_dma = dev->bus_dma_mask;
Again, I think we could just do another min_not_zero() here. A device wired to address only one single page of RAM isn't a realistic prospect (and we could just flip the -1 and the shift in the max_dma calculation if we *really* wanted to support such things).
> + > return (1ULL << (fls64(max_dma) - 1)) * 2 - 1; > } > > static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask, > u64 *phys_mask) > { > + if (dev->bus_dma_mask && dev->bus_dma_mask < dma_mask) > + dma_mask = dev->bus_dma_mask; > +
Similarly, can't we assume dma_mask to be nonzero here too? It feels like we really shouldn't have managed to get this far without one.
Robin.
> if (force_dma_unencrypted()) > *phys_mask = __dma_to_phys(dev, dma_mask); > else > @@ -87,7 +94,7 @@ static gfp_t __dma_direct_optimal_gfp_mask(struct device *dev, u64 dma_mask, > static bool dma_coherent_ok(struct device *dev, phys_addr_t phys, size_t size) > { > return phys_to_dma_direct(dev, phys) + size - 1 <= > - dev->coherent_dma_mask; > + min_not_zero(dev->coherent_dma_mask, dev->bus_dma_mask); > } > > void *dma_direct_alloc_pages(struct device *dev, size_t size, > @@ -291,12 +298,6 @@ int dma_direct_supported(struct device *dev, u64 mask) > if (mask < phys_to_dma(dev, DMA_BIT_MASK(32))) > return 0; > #endif > - /* > - * Upstream PCI/PCIe bridges or SoC interconnects may not carry > - * as many DMA address bits as the device itself supports. > - */ > - if (dev->bus_dma_mask && mask > dev->bus_dma_mask) > - return 0; > return 1; > } > >
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