Hello,
On Wednesday, March 07, 2012 12:22 AM Russell King - ARM Linux wrote:
> On Wed, Feb 29, 2012 at 04:04:22PM +0100, Marek Szyprowski wrote:
> > +static int arm_iommu_mmap_attrs(struct device *dev, struct vm_area_struct *vma,
> > + void *cpu_addr, dma_addr_t dma_addr, size_t size,
> > + struct dma_attrs *attrs)
> > +{
> > + struct arm_vmregion *c;
> > +
> > + vma->vm_page_prot = __get_dma_pgprot(attrs, vma->vm_page_prot);
> > + c = arm_vmregion_find(&consistent_head, (unsigned long)cpu_addr);
>
> What protects this against other insertions/removals from the list?
arm_vmregion_* functions have their own spinlock.
(snipped)
> > + if (c) {
> > + struct page **pages = c->priv;
> > + __dma_free_remap(cpu_addr, size);
> > + __iommu_remove_mapping(dev, handle, size);
> > + __iommu_free_buffer(dev, pages, size);
> > + }
> > +}
> > +
> > +/*
> > + * Map a part of the scatter-gather list into contiguous io address space
> > + */
> > +static int __map_sg_chunk(struct device *dev, struct scatterlist *sg,
> > + size_t size, dma_addr_t *handle,
> > + enum dma_data_direction dir)
> > +{
> > + struct dma_iommu_mapping *mapping = dev->archdata.mapping;
> > + dma_addr_t iova, iova_base;
> > + int ret = 0;
> > + unsigned int count;
> > + struct scatterlist *s;
> > +
> > + size = PAGE_ALIGN(size);
> > + *handle = ARM_DMA_ERROR;
> > +
> > + iova_base = iova = __alloc_iova(mapping, size);
> > + if (iova == ARM_DMA_ERROR)
> > + return -ENOMEM;
> > +
> > + for (count = 0, s = sg; count < (size >> PAGE_SHIFT); s = sg_next(s))
> > + {
> > + phys_addr_t phys = page_to_phys(sg_page(s));
> > + unsigned int len = PAGE_ALIGN(s->offset + s->length);
> > +
> > + if (!arch_is_coherent())
> > + __dma_page_cpu_to_dev(sg_page(s), s->offset, s->length, dir);
> > +
> > + ret = iommu_map(mapping->domain, iova, phys, len, 0);
>
> Dealing with phys addresses on one part and pages + offset + length
> in a different part doesn't look like a good idea. Why can't there
> be some consistency?
Well, I have no idea how to be more consistent here. scatter-lists operates on
pages + offsets + length parameters. iommu api operates on the whole pages, but
they are referred with physical address. Right now I cannot change any of it,
at least not it the near future.
Best regards
--
Marek Szyprowski
Samsung Poland R&D Center
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