drm/msm/a6xx: don't set IO_PGTABLE_QUIRK_ARM_OUTER_WBWA with coherent SMMU

If the Adreno SMMU is dma-coherent, allocation will fail unless we
disable IO_PGTABLE_QUIRK_ARM_OUTER_WBWA. Skip setting this quirk for the
coherent SMMUs (like we have on sm8350 platform).

Fixes: 54af0ceb ("arm64: dts: qcom: sm8350: add GPU, GMU, GPU CC and SMMU nodes")
Reported-by: David Heidelberg <david@ixit.cz>
Signed-off-by: Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
Tested-by: David Heidelberg <david@ixit.cz>
Reviewed-by: Konrad Dybcio <konrad.dybcio@linaro.org>
Tested-by: Konrad Dybcio <konrad.dybcio@linaro.org> # SM8450 HDK
Patchwork: https://patchwork.freedesktop.org/patch/531562/Signed-off-by: Rob Clark <robdclark@chromium.org>

drivers/gpu/drm/msm/adreno/a6xx_gpu.c

@@ -1744,7 +1744,8 @@ a6xx_create_address_space(struct msm_gpu *gpu, struct platform_device *pdev)
 	 * This allows GPU to set the bus attributes required to use system
 	 * cache on behalf of the iommu page table walker.
 	 */
-	if (!IS_ERR_OR_NULL(a6xx_gpu->htw_llc_slice))
+	if (!IS_ERR_OR_NULL(a6xx_gpu->htw_llc_slice) &&
+	    !device_iommu_capable(&pdev->dev, IOMMU_CAP_CACHE_COHERENCY))
 		quirks |= IO_PGTABLE_QUIRK_ARM_OUTER_WBWA;
 
 	return adreno_iommu_create_address_space(gpu, pdev, quirks);