Re: [RFC, v3 9/9] media: platform: Add Mediatek ISP P1 shared memory device

Tomasz Figa
2019-07-23T07:20:23Z

Hi Jungo,

On Fri, Jul 5, 2019 at 4:59 PM Jungo Lin <jungo.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org> wrote:
>
> Hi Tomasz:
>
> On Fri, 2019-07-05 at 13:22 +0900, Tomasz Figa wrote:
> > Hi Jungo,
> >
> > On Fri, Jul 5, 2019 at 12:33 PM Jungo Lin <jungo.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org> wrote:
> > >
> > > Hi Tomasz,
>
> [snip]
>
> > > After applying your suggestion in SCP device driver, we could remove
> > > mtk_cam-smem.h/c. Currently, we use dma_alloc_coherent with SCP device
> > > to get SCP address. We could touch the buffer with this SCP address in
> > > SCP processor.
> > >
> > > After that, we use dma_map_page_attrs with P1 device which supports
> > > IOMMU domain to get IOVA address. For this address, we will assign
> > > it to our ISP HW device to proceed.
> > >
> > > Below is the snippet for ISP P1 compose buffer initialization.
> > >
> > > ptr = dma_alloc_coherent(p1_dev->cam_dev.smem_dev,
> > > MAX_COMPOSER_SIZE, &addr, GFP_KERNEL);
> > > if (!ptr) {
> > > dev_err(dev, "failed to allocate compose memory\n");
> > > return -ENOMEM;
> > > }
> > > isp_ctx->scp_mem_pa = addr;
> >
> > addr contains a DMA address, not a physical address. Could we call it
> > scp_mem_dma instead?
> >
> > > dev_dbg(dev, "scp addr:%pad\n", &addr);
> > >
> > > /* get iova address */
> > > addr = dma_map_page_attrs(dev, phys_to_page(addr), 0,
> >
> > addr is a DMA address, so phys_to_page() can't be called on it. The
> > simplest thing here would be to use dma_map_single() with ptr as the
> > CPU address expected.
> >
>
> We have changed to use ma_map_single() with ptr, but encounter IOMMU
> error. From the debug log of iommu_dma_map_page[3], we got
> 0x0000000054800000 instead of expected address: 0x0000000050800000[2].
> There is a address offset(0x4000000). If we change to use
> dma_map_page_attrs with phys_to_page(addr), the address is correct as we
> expected[2]. Do you have any suggestion on this issue? Do we miss
> something?

Sorry for the late reply. Could you show me the code changes you made
to use dma_map_single()? It would sound like the virtual address
passed to dma_map_single() isn't correct.

Best regards,
Tomasz

>
> [1]
> [ 1.344786] __dma_alloc_from_coherent: 0x800000 PAGE_SHIFT:12
> device_base:0x0000000050000000 dma:0x0000000050800000
> virt_base:ffffff8014000000 va:ffffff8014800000
>
> [ 1.346890] mtk-cam 1a000000.camisp: scp addr:0x0000000050800000
> va:ffffff8014800000
>
> [ 1.347864] iommu_dma_map_page:0x0000000054800000 offset:0
> [ 1.348562] mtk-cam 1a000000.camisp: iova addr:0x00000000fde00000
>
> [2]
> [ 1.346738] __dma_alloc_from_coherent: 0x800000 PAGE_SHIFT:12
> device_base:0x0000000050000000 dma:0x0000000050800000
> virt_base:ffffff8014000000 va:ffffff8014800000
> [ 1.348841] mtk-cam 1a000000.camisp: scp addr:0x0000000050800000
> va:ffffff8014800000
> [ 1.349816] iommu_dma_map_page:0x0000000050800000 offset:0
> [ 1.350514] mtk-cam 1a000000.camisp: iova addr:0x00000000fde00000
>
>
> [3]
> dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
> unsigned long offset, size_t size, int prot)
> {
> phys_addr_t phys = page_to_phys(page);
> pr_err("iommu_dma_map_page:%pa offset:%lu\n", &phys, offset);
>
> return __iommu_dma_map(dev, page_to_phys(page) + offset, size, prot,
> iommu_get_dma_domain(dev));
> }
>
> [snip]
>
> Best regards,
>
> Jungo
>