Message-ID: <7aa025a1-b211-f04c-9169-236102fe27fe@quicinc.com>
Date:   Tue, 21 Feb 2023 13:22:51 -0800
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Subject: Re: [PATCH v10 15/26] gunyah: rsc_mgr: Add platform ops on
 mem_lend/mem_reclaim
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To:     Srinivas Kandagatla <srinivas.kandagatla@linaro.org>,
        Alex Elder <elder@linaro.org>,
        Prakruthi Deepak Heragu <quic_pheragu@quicinc.com>
CC:     Murali Nalajala <quic_mnalajal@quicinc.com>,
        Trilok Soni <quic_tsoni@quicinc.com>,
        Srivatsa Vaddagiri <quic_svaddagi@quicinc.com>,
        Carl van Schaik <quic_cvanscha@quicinc.com>,
        Dmitry Baryshkov <dmitry.baryshkov@linaro.org>,
        Bjorn Andersson <andersson@kernel.org>,
        "Konrad Dybcio" <konrad.dybcio@linaro.org>,
        Arnd Bergmann <arnd@arndb.de>,
        "Greg Kroah-Hartman" <gregkh@linuxfoundation.org>,
        Rob Herring <robh+dt@kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@linaro.org>,
        Jonathan Corbet <corbet@lwn.net>,
        Bagas Sanjaya <bagasdotme@gmail.com>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Jassi Brar <jassisinghbrar@gmail.com>,
        <linux-arm-msm@vger.kernel.org>, <devicetree@vger.kernel.org>,
        <linux-kernel@vger.kernel.org>, <linux-doc@vger.kernel.org>,
        <linux-arm-kernel@lists.infradead.org>
References: <20230214211229.3239350-1-quic_eberman@quicinc.com>
 <20230214212448.3318756-1-quic_eberman@quicinc.com>
 <963d84e8-7b91-c278-1978-4e73d73f7c6f@linaro.org>
From:   Elliot Berman <quic_eberman@quicinc.com>
In-Reply-To: <963d84e8-7b91-c278-1978-4e73d73f7c6f@linaro.org>
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On 2/21/2023 6:51 AM, Srinivas Kandagatla wrote:
> 
> 
> On 14/02/2023 21:24, Elliot Berman wrote:
[snip]
>> +
>> +static struct gunyah_rm_platform_ops *rm_platform_ops;
>> +static DECLARE_RWSEM(rm_platform_ops_lock);
> 
> Why do we need this read/write lock or this global rm_platform_ops here, 
> AFAIU, there will be only one instance of platform_ops per platform.
> 
> This should be a core part of the gunyah and its driver early setup, 
> that should give us pretty much lock less behaviour.
> 
> We should be able to determine by Hypervisor UUID that its on Qualcomm 
> platform or not, during early gunyah setup which should help us setup 
> the platfrom ops accordingly.
> 
> This should also help cleanup some of the gunyah code that was added 
> futher down in this patchset.

I'm guessing the direction to take is:

   config GUNYAH
     select QCOM_SCM if ARCH_QCOM

and have vm_mgr call directly into qcom_scm driver if the UID matches?

We have an Android requirement to enable CONFIG_GUNYAH=y and 
CONFIG_QCOM_SCM=m, but it wouldn't be possible with this design. The 
platform hooks implementation allows GUNYAH and QCOM_SCM to be enabled 
without setting lower bound of the other.

- Elliot