This solves a problem we see with drm/msm, caused by getting iommu_dma_ops while we attach our own domain and manage it directly at the iommu API level: [0000000000000038] user address but active_mm is swapper Internal error: Oops: 96000005 [#1] PREEMPT SMP Modules linked in: CPU: 7 PID: 70 Comm: kworker/7:1 Tainted: G W 4.19.3 #90 Hardware name: xxx (DT) Workqueue: events deferred_probe_work_func pstate: 80c00009 (Nzcv daif +PAN +UAO) pc : iommu_dma_map_sg+0x7c/0x2c8 lr : iommu_dma_map_sg+0x40/0x2c8 sp : ffffff80095eb4f0 x29: ffffff80095eb4f0 x28: 0000000000000000 x27: ffffffc0f9431578 x26: 0000000000000000 x25: 00000000ffffffff x24: 0000000000000003 x23: 0000000000000001 x22: ffffffc0fa9ac010 x21: 0000000000000000 x20: ffffffc0fab40980 x19: ffffffc0fab40980 x18: 0000000000000003 x17: 00000000000001c4 x16: 0000000000000007 x15: 000000000000000e x14: ffffffffffffffff x13: ffff000000000000 x12: 0000000000000028 x11: 0101010101010101 x10: 7f7f7f7f7f7f7f7f x9 : 0000000000000000 x8 : ffffffc0fab409a0 x7 : 0000000000000000 x6 : 0000000000000002 x5 : 0000000100000000 x4 : 0000000000000000 x3 : 0000000000000001 x2 : 0000000000000002 x1 : ffffffc0f9431578 x0 : 0000000000000000 Process kworker/7:1 (pid: 70, stack limit = 0x0000000017d08ffb) Call trace: iommu_dma_map_sg+0x7c/0x2c8 __iommu_map_sg_attrs+0x70/0x84 get_pages+0x170/0x1e8 msm_gem_get_iova+0x8c/0x128 _msm_gem_kernel_new+0x6c/0xc8 msm_gem_kernel_new+0x4c/0x58 dsi_tx_buf_alloc_6g+0x4c/0x8c msm_dsi_host_modeset_init+0xc8/0x108 msm_dsi_modeset_init+0x54/0x18c _dpu_kms_drm_obj_init+0x430/0x474 dpu_kms_hw_init+0x5f8/0x6b4 msm_drm_bind+0x360/0x6c8 try_to_bring_up_master.part.7+0x28/0x70 component_master_add_with_match+0xe8/0x124 msm_pdev_probe+0x294/0x2b4 platform_drv_probe+0x58/0xa4 really_probe+0x150/0x294 driver_probe_device+0xac/0xe8 __device_attach_driver+0xa4/0xb4 bus_for_each_drv+0x98/0xc8 __device_attach+0xac/0x12c device_initial_probe+0x24/0x30 bus_probe_device+0x38/0x98 deferred_probe_work_func+0x78/0xa4 process_one_work+0x24c/0x3dc worker_thread+0x280/0x360 kthread+0x134/0x13c ret_from_fork+0x10/0x18 Code: d2800004 91000725 6b17039f 5400048a (f9401f40) ---[ end trace f22dda57f3648e2c ]--- Kernel panic - not syncing: Fatal exception SMP: stopping secondary CPUs Kernel Offset: disabled CPU features: 0x0,22802a18 Memory Limit: none The problem is that when drm/msm does it's own iommu_attach_device(), now the domain returned by iommu_get_domain_for_dev() is drm/msm's domain, and it doesn't have domain->iova_cookie. We kind of avoided this problem prior to sdm845/dpu because the iommu was attached to the mdp node in dt, which is a child of the toplevel mdss node (which corresponds to the dev passed in dma_map_sg()). But with sdm845, now the iommu is attached at the mdss level so we hit the iommu_dma_ops in dma_map_sg(). But auto allocating/attaching a domain before the driver is probed was already a blocking problem for enabling per-context pagetables for the GPU. This problem is also now solved with this patch. Fixes: 97890ba9289c dma-mapping: detect and configure IOMMU in of_dma_configure Tested-by: Douglas Anderson <dianders@xxxxxxxxxxxx> Signed-off-by: Rob Clark <robdclark@xxxxxxxxx> --- This is an alternative/replacement for [1]. What it lacks in elegance it makes up for in practicality ;-) [1] https://patchwork.freedesktop.org/patch/264930/ drivers/of/device.c | 22 ++++++++++++++++++++++ 1 file changed, 22 insertions(+) diff --git a/drivers/of/device.c b/drivers/of/device.c index 5957cd4fa262..15ffee00fb22 100644 --- a/drivers/of/device.c +++ b/drivers/of/device.c @@ -72,6 +72,14 @@ int of_device_add(struct platform_device *ofdev) return device_add(&ofdev->dev); } +static const struct of_device_id iommu_blacklist[] = { + { .compatible = "qcom,mdp4" }, + { .compatible = "qcom,mdss" }, + { .compatible = "qcom,sdm845-mdss" }, + { .compatible = "qcom,adreno" }, + {} +}; + /** * of_dma_configure - Setup DMA configuration * @dev: Device to apply DMA configuration @@ -164,6 +172,20 @@ int of_dma_configure(struct device *dev, struct device_node *np, bool force_dma) dev_dbg(dev, "device is%sbehind an iommu\n", iommu ? " " : " not "); + /* + * There is at least one case where the driver wants to directly + * manage the IOMMU, but if we end up with iommu dma_ops, that + * interferes with the drivers ability to use dma_map_sg() for + * cache operations. Since we don't currently have a better + * solution, and this code runs before the driver is probed and + * has a chance to intervene, use a simple blacklist to avoid + * ending up with iommu dma_ops: + */ + if (of_match_device(iommu_blacklist, dev)) { + dev_dbg(dev, "skipping iommu hookup\n"); + iommu = NULL; + } + arch_setup_dma_ops(dev, dma_addr, size, iommu, coherent); return 0; -- 2.19.2
