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

[Jungo Lin <jungo.lin-NuS5LvNUpcJWk0Htik3J/w@public.gmane.org>]

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?

[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