hi, Robin, thanks very much for your comments.
On 5/10/2016 6:28 PM, Robin Murphy wrote:
> On 09/05/16 09:00, [email protected] wrote:
> [...]
>> +static void *mtk_iommu_alloc_pgt(struct device *dev, size_t size, gfp_t gfp)
>> +{
>> + dma_addr_t dma;
>> + void *pages = alloc_pages_exact(size, gfp | __GFP_ZERO);
>> +
>> + if (!pages)
>> + return NULL;
>> +
>> + dma = dma_map_single(dev, pages, size, DMA_TO_DEVICE);
>> + if (dma_mapping_error(dev, dma))
>> + goto out_free;
>> + /*
>> + * We depend on the IOMMU being able to work with any physical
>> + * address directly, so if the DMA layer suggests otherwise by
>> + * translating or truncating them, that bodes very badly...
>> + */
>> + if (dma != virt_to_phys(pages))
>> + goto out_unmap;
>
> Given that you've only got a single table to allocate, and at 4MB it has a
> fair chance of failing beyond early boot time, just use dma_alloc_coherent()
> - you don't need to care about the dma <-> phys relationship because you
> don't have multi-level tables to walk. That way, you can get rid of all the
> awkward streaming DMA stuff, and also benefit from CMA to avoid allocation
> failures.
>
thanks, use dma_alloc_coherent is good for me.
>> + kmemleak_ignore(pages);
>> + return pages;
>> +
>> +out_unmap:
>> + dev_err(dev, "Cannot accommodate DMA translation for IOMMU page
>> tables\n");
>> + dma_unmap_single(dev, dma, size, DMA_TO_DEVICE);
>> +out_free:
>> + free_pages_exact(pages, size);
>> + return NULL;
>> +
>> +}
>> +
>> +static void mtk_iommu_free_pgt(struct device *dev, void *pages, size_t size)
>> +{
>> + dma_unmap_single(dev, (dma_addr_t)virt_to_phys(pages),
>> + size, DMA_TO_DEVICE);
>> + free_pages_exact(pages, size);
>> +}
>> +
>> +static int mtk_iommu_domain_finalise(struct mtk_iommu_data *data)
>> +{
>> + struct mtk_iommu_domain *dom = data->m4u_dom;
>> +
>> + spin_lock_init(&dom->pgtlock);
>> +
>> + dom->pgt_va = mtk_iommu_alloc_pgt(data->dev,
>> + dom->pgt_size, GFP_KERNEL);
>> + if (!dom->pgt_va)
>> + return -ENOMEM;
>> +
>> + dom->pgt_pa = virt_to_phys(dom->pgt_va);
>> +
>> + writel(dom->pgt_pa, data->base + REG_MMU_PT_BASE_ADDR);
>> +
>> + dom->cookie = (void *)data;
>> +
>> + return 0;
>> +}
>> +
>> +static struct iommu_domain *mtk_iommu_domain_alloc(unsigned type)
>> +{
>> + struct mtk_iommu_domain *dom;
>> +
>> + if (type != IOMMU_DOMAIN_UNMANAGED)
>> + return NULL;
>> +
>> + dom = kzalloc(sizeof(*dom), GFP_KERNEL);
>> + if (!dom)
>> + return NULL;
>> +
>> + /*
>> + * MTK m4u support 4GB iova address space, and oly support 4K page
>> + * mapping. So the pagetable size should be exactly as 4M.
>> + */
>> + dom->pgt_size = SZ_4M;
>
> If the table size is fixed, then why bother having a variable at all?
>
>> + return &dom->domain;
>> +}
>> +
>> +static void mtk_iommu_domain_free(struct iommu_domain *domain)
>> +{
>> + kfree(to_mtk_domain(domain));
>> +}
>> +
>
> [...]
>
>> +static int mtk_iommu_map(struct iommu_domain *domain, unsigned long iova,
>> + phys_addr_t paddr, size_t size, int prot)
>> +{
>> + struct mtk_iommu_domain *dom = to_mtk_domain(domain);
>> + struct mtk_iommu_data *data = dom->cookie;
>> + unsigned int page_num = size >> MTK_IOMMU_PAGE_SHIFT;
>
> Since you only advertise a single page size, this will always be 1, so you
> could either get rid of the loop here...
>
I would prefer your following advise to change the pgsize_bitmap.
I would follow your advise in the next version.
Thanks very much.
>> + unsigned long flags;
>> + unsigned int i;
>> + u32 *pgt_base_iova;
>> + u32 pabase = (u32)paddr;
>> + int map_size = 0;
>> +
>> + spin_lock_irqsave(&dom->pgtlock, flags);
>> + pgt_base_iova = dom->pgt_va + (iova >> MTK_IOMMU_PAGE_SHIFT);
>> + for (i = 0; i < page_num; i++) {
>> + pgt_base_iova[i] = pabase | F_DESC_VALID | F_DESC_NONSEC;
>> + pabase += MTK_IOMMU_PAGE_SIZE;
>> + map_size += MTK_IOMMU_PAGE_SIZE;
>> + }
>> + dma_sync_single_for_device(data->dev,
>> + dom->pgt_pa + (iova >> MTK_IOMMU_PAGE_SHIFT),
>> + (size >> MTK_IOMMU_PAGE_SHIFT) * sizeof(u32),
>> + DMA_TO_DEVICE);
>> + spin_unlock_irqrestore(&dom->pgtlock, flags);
>> +
>> + mtk_iommu_tlb_flush_range(data, iova, size);
>> +
>> + return map_size;
>> +}
>
> [...]
>
>> +static struct iommu_ops mtk_iommu_ops = {
>> + .domain_alloc = mtk_iommu_domain_alloc,
>> + .domain_free = mtk_iommu_domain_free,
>> + .attach_dev = mtk_iommu_attach_device,
>> + .detach_dev = mtk_iommu_detach_device,
>> + .map = mtk_iommu_map,
>> + .unmap = mtk_iommu_unmap,
>> + .map_sg = default_iommu_map_sg,
>> + .iova_to_phys = mtk_iommu_iova_to_phys,
>> + .add_device = mtk_iommu_add_device,
>> + .remove_device = mtk_iommu_remove_device,
>> + .device_group = mtk_iommu_device_group,
>> + .pgsize_bitmap = MTK_IOMMU_PAGE_SIZE,
>> +};
>
> ...or perhaps advertise .pgsize_bitmap = ~0UL << MTK_IOMMU_PAGE_SHIFT here,
> so you actually can handle multiple entries at once for larger mappings -
> given how simple the page table format is that doesn't seem too unreasonable,
> especially since it should give you a big efficiency win in terms of TLB
> maintenance.
>
> Robin.
>
