[PATCH v12 2/7] iommu/mediatek: Fix two IOMMU share pagetable issue

[Laura Nao]

Hello,

This patch is causing fluster tests to fail on MT8192, IOMMU read and write faults are reported in the log. Here's an extract is from the VP9 tests:

mtk-iommu 1401d000.m4u: fault type=0x280 iova=0x1ff7c0000 pa=0x0 master=0x5000480(larb=5 port=0) layer=0 read
mtk-iommu 1401d000.m4u: fault type=0x280 iova=0x1fe3ee000 pa=0x0 master=0x5000492(larb=5 port=4) layer=0 write

Tests are failing for H264, VP8 and VP9 decoding on next-20230817 with fluster in the same way, complete logs can be found here: 
- H264: https://storage.kernelci.org/next/master/next-20230817/arm64/defconfig+arm64-chromebook+videodec/gcc-10/lab-collabora/v4l2-decoder-conformance-h264-mt8192-asurada-spherion-r0.html
- VP8: https://storage.kernelci.org/next/master/next-20230817/arm64/defconfig+arm64-chromebook+videodec/gcc-10/lab-collabora/v4l2-decoder-conformance-vp8-mt8192-asurada-spherion-r0.html
- VP9: https://storage.kernelci.org/next/master/next-20230817/arm64/defconfig+arm64-chromebook+videodec/gcc-10/lab-collabora/v4l2-decoder-conformance-vp9-mt8192-asurada-spherion-r0.html

Reverting this patch fixes the issue. 

>From my understanding, on MT8192 the 16GB iova space is partitioned between display, vcodec and camera. The iommu domain configuration for vcodec was loaded from frstdata->bank[0]->m4u_dom (vcodec is preassigned to a specific iova range), while after this patch a new pagetable is created instead. 

Do you have any insight on how to fix this while keeping compatibility with MT8188 and MT8195?

Best,

Laura