... > static bool tegra_smmu_capable(enum iommu_cap cap) > @@ -420,17 +413,21 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, > struct tegra_smmu_as *as) > { > u32 value; > - int err; > + int err = 0; > + > + mutex_lock(&smmu->lock); > > if (as->use_count > 0) { > as->use_count++; > - return 0; > + goto err_unlock; This looks a bit odd because it's not a error condition. Perhaps should be better to "goto bump_usecount"? Or make it similar to tegra_smmu_as_unprepare()? > } > > as->pd_dma = dma_map_page(smmu->dev, as->pd, 0, SMMU_SIZE_PD, > DMA_TO_DEVICE); > - if (dma_mapping_error(smmu->dev, as->pd_dma)) > - return -ENOMEM; > + if (dma_mapping_error(smmu->dev, as->pd_dma)) { > + err = -ENOMEM; > + goto err_unlock; > + } > > /* We can't handle 64-bit DMA addresses */ > if (!smmu_dma_addr_valid(smmu, as->pd_dma)) { > @@ -453,24 +450,35 @@ static int tegra_smmu_as_prepare(struct tegra_smmu *smmu, > as->smmu = smmu; bump_usecount: > as->use_count++; > > + mutex_unlock(&smmu->lock); > + > return 0; > > err_unmap: > dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE); > +err_unlock: > + mutex_unlock(&smmu->lock); > + > return err; > } > > static void tegra_smmu_as_unprepare(struct tegra_smmu *smmu, > struct tegra_smmu_as *as) > { > - if (--as->use_count > 0) > + mutex_lock(&smmu->lock); > + > + if (--as->use_count > 0) { > + mutex_unlock(&smmu->lock); > return; > + } > > tegra_smmu_free_asid(smmu, as->id); > > dma_unmap_page(smmu->dev, as->pd_dma, SMMU_SIZE_PD, DMA_TO_DEVICE); > > as->smmu = NULL; > + > + mutex_unlock(&smmu->lock); > } > > static int tegra_smmu_attach_dev(struct iommu_domain *domain, >