linux-kernel - Re: [PATCH v7 1/5] iommu/arm-smmu: re-enable context caching in smmu reset operation

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Date: Wed, 10 Jan 2024 12:00:35 +0100
From: Konrad Dybcio <konrad.dybcio@...aro.org>
To: Bibek Kumar Patro <quic_bibekkum@...cinc.com>, will@...nel.org,
 robin.murphy@....com, joro@...tes.org, dmitry.baryshkov@...aro.org,
 jsnitsel@...hat.com, quic_bjorande@...cinc.com, mani@...nel.org,
 quic_eberman@...cinc.com, robdclark@...omium.org,
 u.kleine-koenig@...gutronix.de, robh@...nel.org, vladimir.oltean@....com,
 quic_pkondeti@...cinc.com, quic_molvera@...cinc.com
Cc: linux-arm-msm@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 iommu@...ts.linux.dev, linux-kernel@...r.kernel.org,
 qipl.kernel.upstream@...cinc.com
Subject: Re: [PATCH v7 1/5] iommu/arm-smmu: re-enable context caching in smmu
 reset operation



On 1/9/24 12:42, Bibek Kumar Patro wrote:
> Default MMU-500 reset operation disables context caching in
> prefetch buffer. It is however expected for context banks using
> the ACTLR register to retain their prefetch value during reset
> and runtime suspend.
> 
> Replace default MMU-500 reset operation with Qualcomm specific reset
> operation which envelope the default reset operation and re-enables
> context caching in prefetch buffer for Qualcomm SoCs.
> 
> Signed-off-by: Bibek Kumar Patro <quic_bibekkum@...cinc.com>
> ---
>   drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c | 37 ++++++++++++++++++++--
>   1 file changed, 34 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> index 549ae4dba3a6..000e207346af 100644
> --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom.c
> @@ -14,6 +14,16 @@
> 
>   #define QCOM_DUMMY_VAL	-1
> 
> +/*
> + * SMMU-500 TRM defines BIT(0) as CMTLB (Enable context caching in the
> + * macro TLB) and BIT(1) as CPRE (Enable context caching in the prefetch
> + * buffer). The remaining bits are implementation defined and vary across
> + * SoCs.
> + */
> +
> +#define CPRE			(1 << 1)
> +#define CMTLB			(1 << 0)
> +
>   static struct qcom_smmu *to_qcom_smmu(struct arm_smmu_device *smmu)
>   {
>   	return container_of(smmu, struct qcom_smmu, smmu);
> @@ -376,11 +386,32 @@ static int qcom_smmu_def_domain_type(struct device *dev)
>   	return match ? IOMMU_DOMAIN_IDENTITY : 0;
>   }
> 
> +static int qcom_smmu500_reset(struct arm_smmu_device *smmu)
> +{
> +	int ret;
> +	u32 val;
> +	int i;
> +
> +	ret = arm_mmu500_reset(smmu);
> +
> +	if (ret)
Weird empty line.. Please remove it in the next revision since you're
already going to send a new one..

Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad