linux-kernel - Re: [PATCH v5 3/6] iommu/qcom: Disable and reset context bank before programming

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Date:   Thu, 22 Jun 2023 11:32:49 +0200
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...labora.com>, agross@...nel.org
Cc:     andersson@...nel.org, luca@...tu.xyz, dmitry.baryshkov@...aro.org,
        joro@...tes.org, will@...nel.org, robin.murphy@....com,
        robh+dt@...nel.org, krzysztof.kozlowski+dt@...aro.org,
        conor+dt@...nel.org, robdclark@...il.com,
        linux-arm-msm@...r.kernel.org, iommu@...ts.linux.dev,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org, kernel@...labora.com
Subject: Re: [PATCH v5 3/6] iommu/qcom: Disable and reset context bank before
 programming

On 22.06.2023 11:27, AngeloGioacchino Del Regno wrote:
> Writing	the new	TTBRs, TCRs and MAIRs on a previously enabled
> context bank may trigger a context fault, resulting in firmware
> driven AP resets: change the domain initialization programming
> sequence to disable the context bank(s) and to also clear the
> related fault address (CB_FAR) and fault status (CB_FSR)
> registers before writing new values to TTBR0/1, TCR/TCR2, MAIR0/1.
> 
> Fixes: 0ae349a0f33f ("iommu/qcom: Add qcom_iommu")
> Signed-off-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> ---
Reviewed-by: Konrad Dybcio <konrad.dybcio@...aro.org>

Konrad
>  drivers/iommu/arm/arm-smmu/qcom_iommu.c | 7 +++++++
>  1 file changed, 7 insertions(+)
> 
> diff --git a/drivers/iommu/arm/arm-smmu/qcom_iommu.c b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> index 8face57c4180..f1bd7c035db8 100644
> --- a/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> +++ b/drivers/iommu/arm/arm-smmu/qcom_iommu.c
> @@ -273,6 +273,13 @@ static int qcom_iommu_init_domain(struct iommu_domain *domain,
>  			ctx->secure_init = true;
>  		}
>  
> +		/* Disable context bank before programming */
> +		iommu_writel(ctx, ARM_SMMU_CB_SCTLR, 0);
> +
> +		/* Clear context bank fault address fault status registers */
> +		iommu_writel(ctx, ARM_SMMU_CB_FAR, 0);
> +		iommu_writel(ctx, ARM_SMMU_CB_FSR, ARM_SMMU_FSR_FAULT);
> +
>  		/* TTBRs */
>  		iommu_writeq(ctx, ARM_SMMU_CB_TTBR0,
>  				pgtbl_cfg.arm_lpae_s1_cfg.ttbr |