linux-kernel - Re: [PATCH v3 5/8] iommu/arm-smmu-qcom: Consistently initialize stream mappings

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Date:   Fri, 11 Sep 2020 08:26:29 +0000
From:   Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Will Deacon <will@...nel.org>, Robin Murphy <robin.murphy@....com>,
        Joerg Roedel <joro@...tes.org>,
        Jordan Crouse <jcrouse@...eaurora.org>,
        Rob Clark <robdclark@...omium.org>,
        Sibi Sankar <sibis@...eaurora.org>,
        linux-arm-kernel@...ts.infradead.org,
        iommu@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org
Subject: Re: [PATCH v3 5/8] iommu/arm-smmu-qcom: Consistently initialize
 stream mappings

On 2020-09-04 21:25, Bjorn Andersson wrote:
> Firmware that traps writes to S2CR to translate BYPASS into FAULT also
> ignores writes of type FAULT. As such booting with "disable_bypass" set
> will result in all S2CR registers left as configured by the bootloader.
> 
> This has been seen to result in indeterministic results, as these
> mappings might linger and reference context banks that Linux is
> reconfiguring.
> 
> Use the fact that BYPASS writes result in FAULT type to force all 
> stream
> mappings to FAULT.
> 
> Signed-off-by: Bjorn Andersson <bjorn.andersson@...aro.org>
> ---

Reviewed-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>
Tested-by: Sai Prakash Ranjan <saiprakash.ranjan@...eaurora.org>


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