[PATCH v4 2/2] drm/msm: Be more shouty if per-process pgtables aren't working

[Rob Clark]

From: Rob Clark <robdcl...@chromium.org>

Otherwise it is not always obvious if a dt or iommu change is causing us
to fall back to global pgtable.

Signed-off-by: Rob Clark <robdcl...@chromium.org>
---
 drivers/gpu/drm/msm/msm_iommu.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/msm/msm_iommu.c b/drivers/gpu/drm/msm/msm_iommu.c
index 418e1e06cdde..9b19124c9bd0 100644
--- a/drivers/gpu/drm/msm/msm_iommu.c
+++ b/drivers/gpu/drm/msm/msm_iommu.c
@@ -227,21 +227,26 @@ struct msm_mmu *msm_iommu_pagetable_create(struct msm_mmu 
*parent)
        struct adreno_smmu_priv *adreno_smmu = dev_get_drvdata(parent->dev);
        struct msm_iommu *iommu = to_msm_iommu(parent);
        struct msm_iommu_pagetable *pagetable;
        const struct io_pgtable_cfg *ttbr1_cfg = NULL;
        struct io_pgtable_cfg ttbr0_cfg;
        int ret;
 
        /* Get the pagetable configuration from the domain */
        if (adreno_smmu->cookie)
                ttbr1_cfg = adreno_smmu->get_ttbr1_cfg(adreno_smmu->cookie);
-       if (!ttbr1_cfg)
+
+       /*
+        * If you hit this WARN_ONCE() you are probably missing an entry in
+        * qcom_smmu_impl_of_match[] in arm-smmu-qcom.c
+        */
+       if (WARN_ONCE(!ttbr1_cfg, "No per-process page tables"))
                return ERR_PTR(-ENODEV);
 
        pagetable = kzalloc(sizeof(*pagetable), GFP_KERNEL);
        if (!pagetable)
                return ERR_PTR(-ENOMEM);
 
        msm_mmu_init(&pagetable->base, parent->dev, &pagetable_funcs,
                MSM_MMU_IOMMU_PAGETABLE);
 
        /* Clone the TTBR1 cfg as starting point for TTBR0 cfg: */
-- 
2.40.1