[PATCH v3 2/2] drm/msm: Be more shouty if per-process pgtables aren't working

[Rob Clark <robdclark@gmail.com>]

From: Rob Clark <robdclark@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 <robdclark@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