[PATCH] of/device: add blacklist for iommu dma_ops

[Rob Clark]

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 at chromium.org>
Signed-off-by: Rob Clark <robdclark at gmail.com>
---
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