| Message ID | 20180110080027.13879-32-hch@lst.de (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
On 10/01/18 08:00, Christoph Hellwig wrote: > Signed-off-by: Christoph Hellwig <hch@lst.de> > --- > include/linux/dma-direct.h | 1 + > lib/dma-direct.c | 19 +++++++++++++++++++ > 2 files changed, 20 insertions(+) > > diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h > index 4788bf0bf683..bcdb1a3e4b1f 100644 > --- a/include/linux/dma-direct.h > +++ b/include/linux/dma-direct.h > @@ -42,5 +42,6 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, > gfp_t gfp, unsigned long attrs); > void dma_direct_free(struct device *dev, size_t size, void *cpu_addr, > dma_addr_t dma_addr, unsigned long attrs); > +int dma_direct_supported(struct device *dev, u64 mask); > > #endif /* _LINUX_DMA_DIRECT_H */ > diff --git a/lib/dma-direct.c b/lib/dma-direct.c > index 784a68dfdbe3..40b1f92f2214 100644 > --- a/lib/dma-direct.c > +++ b/lib/dma-direct.c > @@ -122,6 +122,24 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, > return nents; > } > > +int dma_direct_supported(struct device *dev, u64 mask) > +{ > +#ifdef CONFIG_ZONE_DMA > + if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) > + return 0; > +#else > + /* > + * Because 32-bit DMA masks are so common we expect every architecture > + * to be able to satisfy them - either by not supporting more physical > + * memory, or by providing a ZONE_DMA32. If neither is the case, the > + * architecture needs to use an IOMMU instead of the direct mapping. > + */ > + if (mask < DMA_BIT_MASK(32)) > + return 0; Do you think it's worth the effort to be a little more accommodating here? i.e.: return dma_max_pfn(dev) >= max_pfn; We seem to have a fair few 28-31 bit masks for older hardware which probably associates with host systems packing equivalently small amounts of RAM. Otherwise though, Reviewed-by: Robin Murphy <robin.murphy@arm.com> Robin. > +#endif > + return 1; > +} > + > static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr) > { > return dma_addr == DIRECT_MAPPING_ERROR; > @@ -132,6 +150,7 @@ const struct dma_map_ops dma_direct_ops = { > .free = dma_direct_free, > .map_page = dma_direct_map_page, > .map_sg = dma_direct_map_sg, > + .dma_supported = dma_direct_supported, > .mapping_error = dma_direct_mapping_error, > }; > EXPORT_SYMBOL(dma_direct_ops); > -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Wed, Jan 10, 2018 at 11:49:34AM +0000, Robin Murphy wrote: >> +#ifdef CONFIG_ZONE_DMA >> + if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) >> + return 0; >> +#else >> + /* >> + * Because 32-bit DMA masks are so common we expect every architecture >> + * to be able to satisfy them - either by not supporting more physical >> + * memory, or by providing a ZONE_DMA32. If neither is the case, the >> + * architecture needs to use an IOMMU instead of the direct mapping. >> + */ >> + if (mask < DMA_BIT_MASK(32)) >> + return 0; > > Do you think it's worth the effort to be a little more accommodating here? > i.e.: > > return dma_max_pfn(dev) >= max_pfn; > > We seem to have a fair few 28-31 bit masks for older hardware which > probably associates with host systems packing equivalently small amounts of > RAM. And those devices don't have a ZONE_DMA? I think we could do something like that, but I'd rather have it as a separate commit with a good explanation. Maybe you can just send on on top of the series? -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On 10/01/18 15:32, Christoph Hellwig wrote: > On Wed, Jan 10, 2018 at 11:49:34AM +0000, Robin Murphy wrote: >>> +#ifdef CONFIG_ZONE_DMA >>> + if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) >>> + return 0; >>> +#else >>> + /* >>> + * Because 32-bit DMA masks are so common we expect every architecture >>> + * to be able to satisfy them - either by not supporting more physical >>> + * memory, or by providing a ZONE_DMA32. If neither is the case, the >>> + * architecture needs to use an IOMMU instead of the direct mapping. >>> + */ >>> + if (mask < DMA_BIT_MASK(32)) >>> + return 0; >> >> Do you think it's worth the effort to be a little more accommodating here? >> i.e.: >> >> return dma_max_pfn(dev) >= max_pfn; >> >> We seem to have a fair few 28-31 bit masks for older hardware which >> probably associates with host systems packing equivalently small amounts of >> RAM. > > And those devices don't have a ZONE_DMA? I think we could do something > like that, but I'd rather have it as a separate commit with a good > explanation. Maybe you can just send on on top of the series? Good point - other than the IXP4xx platform and possibly the Broadcom network drivers, it's probably only x86-relevant stuff where the concern is moot. Let's just keep the simple assumption then, until actually proven otherwise. Robin. -- To unsubscribe from this list: send the line "unsubscribe linux-sh" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/include/linux/dma-direct.h b/include/linux/dma-direct.h index 4788bf0bf683..bcdb1a3e4b1f 100644 --- a/include/linux/dma-direct.h +++ b/include/linux/dma-direct.h @@ -42,5 +42,6 @@ void *dma_direct_alloc(struct device *dev, size_t size, dma_addr_t *dma_handle, gfp_t gfp, unsigned long attrs); void dma_direct_free(struct device *dev, size_t size, void *cpu_addr, dma_addr_t dma_addr, unsigned long attrs); +int dma_direct_supported(struct device *dev, u64 mask); #endif /* _LINUX_DMA_DIRECT_H */ diff --git a/lib/dma-direct.c b/lib/dma-direct.c index 784a68dfdbe3..40b1f92f2214 100644 --- a/lib/dma-direct.c +++ b/lib/dma-direct.c @@ -122,6 +122,24 @@ static int dma_direct_map_sg(struct device *dev, struct scatterlist *sgl, return nents; } +int dma_direct_supported(struct device *dev, u64 mask) +{ +#ifdef CONFIG_ZONE_DMA + if (mask < DMA_BIT_MASK(ARCH_ZONE_DMA_BITS)) + return 0; +#else + /* + * Because 32-bit DMA masks are so common we expect every architecture + * to be able to satisfy them - either by not supporting more physical + * memory, or by providing a ZONE_DMA32. If neither is the case, the + * architecture needs to use an IOMMU instead of the direct mapping. + */ + if (mask < DMA_BIT_MASK(32)) + return 0; +#endif + return 1; +} + static int dma_direct_mapping_error(struct device *dev, dma_addr_t dma_addr) { return dma_addr == DIRECT_MAPPING_ERROR; @@ -132,6 +150,7 @@ const struct dma_map_ops dma_direct_ops = { .free = dma_direct_free, .map_page = dma_direct_map_page, .map_sg = dma_direct_map_sg, + .dma_supported = dma_direct_supported, .mapping_error = dma_direct_mapping_error, }; EXPORT_SYMBOL(dma_direct_ops);
Signed-off-by: Christoph Hellwig <hch@lst.de> --- include/linux/dma-direct.h | 1 + lib/dma-direct.c | 19 +++++++++++++++++++ 2 files changed, 20 insertions(+)