Date:   Tue, 21 Mar 2023 11:50:32 +0100
From:   Johan Hovold <johan@kernel.org>
To:     Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>
Cc:     will@kernel.org, joro@8bytes.org, robin.murphy@arm.com,
        andersson@kernel.org, johan+linaro@kernel.org, steev@kali.org,
        linux-arm-kernel@lists.infradead.org, iommu@lists.linux.dev,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH v4] iommu/arm-smmu-qcom: Limit the SMR groups to 128
Message-ID: <ZBmL+FW44VjxycaA@hovoldconsulting.com>
References: <20230321091332.18334-1-manivannan.sadhasivam@linaro.org>
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On Tue, Mar 21, 2023 at 02:43:32PM +0530, Manivannan Sadhasivam wrote:
> On some Qualcomm platforms, the hypervisor emulates more than 128 SMR
> (Stream Matching Register) groups. This doesn't conform to the ARM SMMU
> architecture specification which defines the range of 0-127. Moreover, the
> emulated groups don't exhibit the same behavior as the architecture
> supported ones.
> 
> For instance, emulated groups will not detect the quirky behavior of some
> firmware versions intercepting writes to S2CR register, thus skipping the
> quirk implemented in the driver and causing boot crash.
> 
> So let's limit the groups to 128 and issue a notice to users in that case.
> 
> Signed-off-by: Manivannan Sadhasivam <manivannan.sadhasivam@linaro.org>

Reviewed-by: Johan Hovold <johan+linaro@kernel.org>
Tested-by: Johan Hovold <johan+linaro@kernel.org>

Johan