Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::3:2 as permitted sender) client-ip=2620:137:e000::3:2;
Message-ID: <47f40099-4215-4c9e-9b7a-c5b981abc589@quicinc.com>
Date:   Thu, 30 Nov 2023 17:19:14 +0200
MIME-Version: 1.0
User-Agent: Mozilla Thunderbird
Subject: Re: [PATCH v2 0/6] Add support for Translation Buffer Units
To:     Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
        <robh+dt@kernel.org>, <krzysztof.kozlowski+dt@linaro.org>,
        <conor+dt@kernel.org>, <will@kernel.org>, <robin.murphy@arm.com>,
        <joro@8bytes.org>
CC:     <devicetree@vger.kernel.org>, <andersson@kernel.org>,
        <konrad.dybcio@linaro.org>, <linux-arm-kernel@lists.infradead.org>,
        <iommu@lists.linux.dev>, <linux-kernel@vger.kernel.org>,
        <linux-arm-msm@vger.kernel.org>, <quic_cgoldswo@quicinc.com>,
        <quic_sukadev@quicinc.com>, <quic_pdaly@quicinc.com>,
        <quic_sudaraja@quicinc.com>, <djakov@kernel.org>
References: <20231118042730.2799-1-quic_c_gdjako@quicinc.com>
 <fe74b1ab-078d-4c53-9133-cf7ab00a656d@linaro.org>
Content-Language: en-US
From:   Georgi Djakov <quic_c_gdjako@quicinc.com>
In-Reply-To: <fe74b1ab-078d-4c53-9133-cf7ab00a656d@linaro.org>
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: 8bit
Precedence: bulk

On 11/18/2023 1:21 PM, Bryan O'Donoghue wrote:
> On 18/11/2023 04:27, Georgi Djakov wrote:
>> The TCUs (Translation Control Units) and TBUs (Translation Buffer
>> Units) are key components of the MMU-500. Multiple TBUs are connected
>> to a single TCU over an interconnect. Each TBU contains a TLB that
>> caches page tables. The MMU-500 implements a TBU for each connected
>> master, and the TBU is designed, so that it is local to the master.
>>
>> The Qualcomm SDM845 platform has an implementation of the SMMU-500,
>> that has multiple TBUs. A DT schema is added to describe the resources
>> for each TBU (register space, power-domains, interconnects and clocks).
>>
>> The TBU driver will manage the resources and allow the system to
>> operate the TBUs during a context fault to obtain details by doing
>> s1 inv, software + hardware page table walks etc. This is implemented
>> with ATOS/eCATs as the ATS feature is not supported. Being able to
>> query the TBUs is useful for debugging various hardware/software
>> issues on these platforms.
>>
>> v2:
>> - Improve DT binding description, add full example. (Konrad)
>> - Drop Qcom specific stuff from the generic binding. (Rob)
>> - Unconditionally try to populate subnodes. (Konrad)
>> - Improve TBU driver commit text, remove memory barriers. (Bjorn)
>> - Move TBU stuff into separate file. Make the driver builtin.
>> - TODO: Evaluate whether to keep TBU support as a separate driver
>>    or just instantiate things from qcom_smmu_impl_init()
>>
>> v1: https://lore.kernel.org/r/20231019021923.13939-1-quic_c_gdjako@quicinc.com
> 
> What is your suggested way to test this series ?

Hi Bryan,

Just break some driver to initiate a memory transaction with no valid context. I used venus for that. Or the simplest would be to just specify an invalid stream ID in DT for some device.

Thanks,
Georgi