[PATCH 0/4] IOMMU driver improvements for modern Exynos SysMMUs
Markuss Broks via B4 Relay <[email protected]>
| Newsgroups | dev.linux.lists.iommu,org.infradead.lists.linux-arm-kernel,org.kernel.feeds.b4-sent,org.kernel.vger.linux-kernel,org.kernel.vger.linux-samsung-soc |
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| Message-ID | <[email protected]> |
Newer SysMMU v7+ instances can lack BLOCK mode: CAPA1 bit 15 reports that the CTRL_BLOCK function is not implemented, and MMU_STATUS never reports a blocked state. The SysMMUs on Exynos 8835 are such instances. The driver currently assumes blocking always works, with two consequences on such hardware: The enable path writes CTRL_BLOCK first, which there acts as a plain enable and starts translation before the page table base is programmed. Worse, both TLB invalidation paths gate the invalidation writes on sysmmu_block() succeeding, which it never does - so every unmap silently skips the invalidation. A stale TLB entry is a valid entry pointing at a freed page, so nothing ever faults: the device reads back garbage and its writebacks corrupt whatever the kernel has since reused those pages for. This was tracked down on Exynos 8835 with the MFC, where the first decoder session of a boot worked and later sessions produced garbage along with random kernel memory corruption. Patches 1-3 add detection of the capability bit and adapt the enable sequence and the invalidation paths, matching the vendor driver's handling of these parts. Patch 4 is an independent debugging improvement: decode the v7 fault transaction info word (AxID/AxLEN), which identifies the issuing port when a master containing several DMA engines faults. Tested on the Samsung Galaxy Tab S9 FE (Exynos 8835/Exynos 1380). Signed-off-by: Markuss Broks <[email protected]> --- Markuss Broks (4): iommu/exynos: detect SysMMUs without BLOCK mode iommu/exynos: fix the enable sequence for no-block SysMMUs iommu/exynos: fix TLB invalidation for no-block SysMMUs iommu/exynos: decode the v7 fault transaction info drivers/iommu/exynos-iommu.c | 37 +++++++++++++++++++++++++++++++++---- 1 file changed, 33 insertions(+), 4 deletions(-) --- base-commit: 415606a7be939835db9b0d6b711887586646346d change-id: 20260820-exynos-iommu-fixes-e0e4d8f0fc06 Best regards, -- Markuss Broks <[email protected]>