Messages in this thread | | | Date | Tue, 27 Oct 2020 17:48:58 +0100 | From | Christoph Hellwig <> | Subject | Re: [PATCH kernel v2 1/2] dma: Allow mixing bypass and normal IOMMU operation |
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> +static inline bool dma_handle_direct(struct device *dev, dma_addr_t dma_handle) > +{ > + return dma_handle >= dev->archdata.dma_offset; > +}
This won't compile except for powerpc, and directly accesing arch members in common code is a bad idea. Maybe both your helpers need to be supplied by arch code to better abstract this out.
> if (dma_map_direct(dev, ops)) > addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit && > + can_map_direct(dev, (phys_addr_t) page_to_phys(page) + offset + size)) > + addr = dma_direct_map_page(dev, page, offset, size, dir, attrs); > +#endif
I don't think page_to_phys needs a phys_addr_t on the return value. I'd also much prefer if we make this a little more beautiful, here are a few suggestions:
- hide the bus_dma_limit check inside can_map_direct, and provide a stub so that we can avoid the ifdef - use a better name for can_map_direct, and maybe also a better calling convention by passing the page (the sg code also has the page), and maybe even hide the dma_map_direct inside it.
if (dma_map_direct(dev, ops) || arch_dma_map_page_direct(dev, page, offset, size)) addr = dma_direct_map_page(dev, page, offset, size, dir, attrs);
> BUG_ON(!valid_dma_direction(dir)); > if (dma_map_direct(dev, ops)) > dma_direct_unmap_page(dev, addr, size, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit && dma_handle_direct(dev, addr + size)) > + dma_direct_unmap_page(dev, addr, size, dir, attrs); > +#endif
Same here.
> if (dma_map_direct(dev, ops)) > ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); > +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + else if (dev->bus_dma_limit) { > + struct scatterlist *s; > + bool direct = true; > + int i; > + > + for_each_sg(sg, s, nents, i) { > + direct = can_map_direct(dev, sg_phys(s) + s->offset + s->length); > + if (!direct) > + break; > + } > + if (direct) > + ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); > + else > + ents = ops->map_sg(dev, sg, nents, dir, attrs); > + } > +#endif
This needs to go into a helper as well. I think the same style as above would work pretty nicely as well:
if (dma_map_direct(dev, ops) || arch_dma_map_sg_direct(dev, sg, nents)) ents = dma_direct_map_sg(dev, sg, nents, dir, attrs); else ents = ops->map_sg(dev, sg, nents, dir, attrs);
> +#ifdef CONFIG_DMA_OPS_BYPASS_BUS_LIMIT > + if (dev->bus_dma_limit) { > + struct scatterlist *s; > + bool direct = true; > + int i; > + > + for_each_sg(sg, s, nents, i) { > + direct = dma_handle_direct(dev, s->dma_address + s->length); > + if (!direct) > + break; > + } > + if (direct) { > + dma_direct_unmap_sg(dev, sg, nents, dir, attrs); > + return; > + } > + } > +#endif
One more time here..
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