Re: [PATCH 2/2] iommu/arm-smmu: Allow client devices to select direct mapping

[Evan Green <evgreen@chromium.org>]

On Wed, Jan 22, 2020 at 3:48 AM Sai Prakash Ranjan
<saiprakash.ranjan@codeaurora.org> wrote:
>
> From: Jordan Crouse <jcrouse@codeaurora.org>
>
> Some client devices want to directly map the IOMMU themselves instead
> of using the DMA domain. Allow those devices to opt in to direct
> mapping by way of a list of compatible strings.
>
> Signed-off-by: Jordan Crouse <jcrouse@codeaurora.org>
> Co-developed-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> Signed-off-by: Sai Prakash Ranjan <saiprakash.ranjan@codeaurora.org>
> ---
>  drivers/iommu/arm-smmu-qcom.c | 39 +++++++++++++++++++++++++++++++++++
>  drivers/iommu/arm-smmu.c      |  3 +++
>  drivers/iommu/arm-smmu.h      |  5 +++++
>  3 files changed, 47 insertions(+)
>
> diff --git a/drivers/iommu/arm-smmu-qcom.c b/drivers/iommu/arm-smmu-qcom.c
> index 64a4ab270ab7..ff746acd1c81 100644
> --- a/drivers/iommu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm-smmu-qcom.c
> @@ -3,6 +3,7 @@
>   * Copyright (c) 2019, The Linux Foundation. All rights reserved.
>   */
>
> +#include <linux/of_device.h>
>  #include <linux/qcom_scm.h>
>
>  #include "arm-smmu.h"
> @@ -11,6 +12,43 @@ struct qcom_smmu {
>         struct arm_smmu_device smmu;
>  };
>
> +static const struct arm_smmu_client_match_data qcom_adreno = {
> +       .direct_mapping = true,
> +};
> +
> +static const struct arm_smmu_client_match_data qcom_mdss = {
> +       .direct_mapping = true,

I don't actually see direct_mapping being used. Shouldn't this member
be checked somewhere?

-Evan