linux-kernel - Re: [RESEND PATCH v17 5/5] iommu/arm-smmu: Add support for qcom,smmu-v2 variant

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Message-ID: <20181121173803.GB9801@arm.com>
Date:   Wed, 21 Nov 2018 17:38:03 +0000
From:   Will Deacon <will.deacon@....com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>,
        thor.thayer@...ux.intel.com
Cc:     joro@...tes.org, robh+dt@...nel.org, robin.murphy@....com,
        iommu@...ts.linux-foundation.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, alex.williamson@...hat.com,
        mark.rutland@....com, rjw@...ysocki.net, robdclark@...il.com,
        linux-pm@...r.kernel.org, freedreno@...ts.freedesktop.org,
        sboyd@...nel.org, tfiga@...omium.org, jcrouse@...eaurora.org,
        sricharan@...eaurora.org, m.szyprowski@...sung.com,
        architt@...eaurora.org, linux-arm-msm@...r.kernel.org
Subject: Re: [RESEND PATCH v17 5/5] iommu/arm-smmu: Add support for
 qcom,smmu-v2 variant

[+Thor]

On Fri, Nov 16, 2018 at 04:54:30PM +0530, Vivek Gautam wrote:
> qcom,smmu-v2 is an arm,smmu-v2 implementation with specific
> clock and power requirements.
> On msm8996, multiple cores, viz. mdss, video, etc. use this
> smmu. On sdm845, this smmu is used with gpu.
> Add bindings for the same.
> 
> Signed-off-by: Vivek Gautam <vivek.gautam@...eaurora.org>
> Reviewed-by: Rob Herring <robh@...nel.org>
> Reviewed-by: Tomasz Figa <tfiga@...omium.org>
> Tested-by: Srinivas Kandagatla <srinivas.kandagatla@...aro.org>
> Reviewed-by: Robin Murphy <robin.murphy@....com>
> ---
>  drivers/iommu/arm-smmu.c | 13 +++++++++++++
>  1 file changed, 13 insertions(+)
> 
> diff --git a/drivers/iommu/arm-smmu.c b/drivers/iommu/arm-smmu.c
> index 2098c3141f5f..d315ca637097 100644
> --- a/drivers/iommu/arm-smmu.c
> +++ b/drivers/iommu/arm-smmu.c
> @@ -120,6 +120,7 @@ enum arm_smmu_implementation {
>  	GENERIC_SMMU,
>  	ARM_MMU500,
>  	CAVIUM_SMMUV2,
> +	QCOM_SMMUV2,
>  };
>  
>  struct arm_smmu_s2cr {
> @@ -2026,6 +2027,17 @@ ARM_SMMU_MATCH_DATA(arm_mmu401, ARM_SMMU_V1_64K, GENERIC_SMMU);
>  ARM_SMMU_MATCH_DATA(arm_mmu500, ARM_SMMU_V2, ARM_MMU500);
>  ARM_SMMU_MATCH_DATA(cavium_smmuv2, ARM_SMMU_V2, CAVIUM_SMMUV2);
>  
> +static const char * const qcom_smmuv2_clks[] = {
> +	"bus", "iface",
> +};
> +
> +static const struct arm_smmu_match_data qcom_smmuv2 = {
> +	.version = ARM_SMMU_V2,
> +	.model = QCOM_SMMUV2,
> +	.clks = qcom_smmuv2_clks,
> +	.num_clks = ARRAY_SIZE(qcom_smmuv2_clks),
> +};

These seems redundant if we go down the route proposed by Thor, where we
just pull all of the clocks out of the device-tree. In which case, why
do we need this match_data at all?

Will