The commit has been introduced in mainline v6.15-rc1. I've also tested
in
v6.15, v6.15.2, and v6.16-rc2, and there have been no apparent
changes.
I've tried to revert the commit, and it does work that way. But on
reading
the commit message I understand that I need to find a proper solution
here.
I've tried to skim down the revert, and this is what I get - if i
change
line [4] as follows:
- dev->bus->dma_configure(dev);
+ if (!strcmp(dev_name(dev), "14830000.decon"))
+ dev->bus->dma_configure(dev);
It really doesn't like dma_configure for some reason. It works, but:
[ 2.779291] exynos-decon 14830000.decon: late IOMMU probe at driver
bind, something fishy here!
I believe the IOMMU hardware doesn't like the fact that it is being
initialized/resumed too early. I formed this conclusion by comparing
the
logs:
mainline:
[ 1.274575] I_HAVE_ADDED_THESE: SYSMMU: exynos_sysmmu_resume enter
[ 2.859656] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable enter
[ 2.864192] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable_clocks
enter
[ 2.869299] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000000 val
0x00000007
[ 2.875062] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_init_config enter
[ 2.880006] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000004 val
0x01100784
[ 2.885819] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_set_ptbase enter
[ 2.890677] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x0000000c val
0x00044a14
[ 2.896490] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_tlb_invalidate
enter
[ 2.901695] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000010 val
0x00000001
[ 2.907507] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable_vid enter
[ 2.912366] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000000 val
0x00000005
[ 2.912371] I_HAVE_ADDED_THESE: SYSMMU: exynos_sysmmu_irq enter
[ 2.912836] [drm] Exynos DRM: using 14830000.decon device for DMA
mapping operations
[ 2.918175] I_HAVE_ADDED_THESE: SYSMMU:
exynos_sysmmu_v5_get_fault_info enter
[ 2.918182] I_HAVE_ADDED_THESE: SYSMMU: show_fault_information
enter
[ 2.918189] exynos-sysmmu 14860000.sysmmu: 14830000.decon: [READ]
PAGE FAULT occurred at 0x6715b3e0
[ 2.918199] exynos-sysmmu 14860000.sysmmu: Page table base:
0x0000000044a14000
[ 2.918243] exynos-drm exynos-drm: bound 14830000.decon (ops
decon_component_ops)
[ 2.922859] I_HAVE_ADDED_THESE: SYSMMU: section_entry enter
[ 2.922864] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 2.922868] exynos-sysmmu 14860000.sysmmu: Lv1 entry: 0x4205001
[ 2.922877] Kernel panic - not syncing: Unrecoverable System MMU
Fault!
and with the patch above applied:
[ 3.018478] [drm] Exynos DRM: using 14830000.decon device for DMA
mapping operations
[ 3.025794] exynos-drm exynos-drm: bound 14830000.decon (ops
decon_component_ops)
[ 3.058655] exynos-dsi 14800000.dsi: [drm:samsung_dsim_host_attach]
Attached td4300-panel device (lanes:4 bpp:24 mode-flags:0x23)
[ 3.070189] exynos-drm exynos-drm: bound 14800000.dsi (ops
exynos_dsi_component_ops)
[ 3.078506] [drm] Initialized exynos 1.1.0 for exynos-drm on minor
1
[ 3.090747] I_HAVE_ADDED_THESE: SYSMMU: exynos_iommu_map enter
[ 3.090845] I_HAVE_ADDED_THESE: SYSMMU: to_exynos_domain enter
[ 3.093325] I_HAVE_ADDED_THESE: SYSMMU: section_entry enter
[ 3.097662] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 3.102000] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 3.106337] I_HAVE_ADDED_THESE: SYSMMU: lv1set_section enter
[ 3.110762] I_HAVE_ADDED_THESE: SYSMMU: exynos_iommu_set_pte enter
[ 3.115726] I_HAVE_ADDED_THESE: SYSMMU: exynos_iommu_map enter
[ 3.120317] I_HAVE_ADDED_THESE: SYSMMU: to_exynos_domain enter
[ 3.124914] I_HAVE_ADDED_THESE: SYSMMU: section_entry enter
[ 3.129240] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 3.133578] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 3.137916] I_HAVE_ADDED_THESE: SYSMMU: lv1set_section enter
[ 3.142340] I_HAVE_ADDED_THESE: SYSMMU: exynos_iommu_set_pte enter
[ ...] (a lot of repetitions later)
[ 4.322904] I_HAVE_ADDED_THESE: SYSMMU: section_entry enter
[ 4.327230] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 4.331567] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 4.335905] I_HAVE_ADDED_THESE: SYSMMU: alloc_lv2entry enter
[ 4.340329] I_HAVE_ADDED_THESE: SYSMMU: page_entry enter
[ 4.344407] I_HAVE_ADDED_THESE: SYSMMU: lv2ent_offset enter
[ 4.348744] I_HAVE_ADDED_THESE: SYSMMU: lv1ent_offset enter
[ 4.353082] I_HAVE_ADDED_THESE: SYSMMU: lv2set_page enter
[ 4.357246] I_HAVE_ADDED_THESE: SYSMMU: exynos_iommu_set_pte enter
[ 4.362751] I_HAVE_ADDED_THESE: SYSMMU: exynos_sysmmu_resume enter
[ 4.362767] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable enter
[ 4.362771] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable_clocks
enter
[ 4.362777] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000000 val
0x00000007
[ 4.362782] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_init_config enter
[ 4.362786] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000004 val
0x01100784
[ 4.362791] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_set_ptbase enter
[ 4.362795] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x0000000c val
0x00042a64
[ 4.362799] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_tlb_invalidate
enter
[ 4.362803] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000010 val
0x00000001
[ 4.362808] I_HAVE_ADDED_THESE: SYSMMU: __sysmmu_enable_vid enter
[ 4.362811] I_HAVE_ADDED_THESE: SYSMMU: write: reg 0x00000000 val
0x00000005
Then it continues booting as usual.
My lack of understanding of the IOMMU and DRM subsystems are really
limiting my triaging capabilities here, therefore I ask for any form
guidance or assistance with this.
Thank you.
[1]
https://lore.kernel.org/r/20250612-exynosdrm-decon-v2-0-d6c1d21c8...@disroot.org
[2]
https://lore.kernel.org/all/20250612-exynos7870-drm-dts-v1-2-88c0779af...@disroot.org
[3]
https://lore.kernel.org/all/20250612-exynos7870-drm-dts-v1-3-88c0779af...@disroot.org
[4]
https://elixir.bootlin.com/linux/v6.16-rc2/source/drivers/iommu/iommu.c#L431
