linux-kernel - Re: [PATCH 06/11] firmware: qcom-shm-bridge: new driver

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Message-ID: <587b738c-118a-5e1e-bb6b-ea3ca2b93234@linaro.org>
Date:   Wed, 30 Aug 2023 16:31:21 +0200
From:   Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
To:     Bartosz Golaszewski <bartosz.golaszewski@...aro.org>
Cc:     Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Konrad Dybcio <konrad.dybcio@...aro.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Conor Dooley <conor+dt@...nel.org>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will@...nel.org>, Arnd Bergmann <arnd@...db.de>,
        Alex Elder <elder@...aro.org>,
        Srini Kandagatla <srinivas.kandagatla@...aro.org>,
        kernel@...cinc.com, linux-arm-msm@...r.kernel.org,
        devicetree@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 06/11] firmware: qcom-shm-bridge: new driver

On 30/08/2023 15:09, Bartosz Golaszewski wrote:

>>>>> +
>>>>> +     return gen_pool_virt_to_phys(pool->genpool, (unsigned long)vaddr);
>>>>> +}
>>>>> +EXPORT_SYMBOL_GPL(qcom_shm_bridge_to_phys_addr);
>>>>> +
>>>>> +static int qcom_shm_bridge_probe(struct platform_device *pdev)
>>>>> +{
>>>>> +     struct qcom_shm_bridge_pool *default_pool;
>>>>> +     struct device *dev = &pdev->dev;
>>>>> +     int ret;
>>>>> +
>>>>> +     /*
>>>>> +      * We need to wait for the SCM device to be created and bound to the
>>>>> +      * SCM driver.
>>>>> +      */
>>>>> +     if (!qcom_scm_is_available())
>>>>> +             return -EPROBE_DEFER;
>>>>
>>>> I think we miss here (and in all other drivers) device links to qcm.
>>>>
>>>
>>> Well, SCM, once probed, cannot be unbound. What would device links
>>> guarantee above that?
>>
>> Runtime PM, probe ordering (dependencies) detection.
>>
> 
> Shouldn't we cross that bridge when we get there? SCM has no support
> for runtime PM. Probe ordering is quite well handled with a simple
> probe deferral. This is also not a parent-child relationship. SHM
> Bridge calls into the trustzone using SCM, but SCM is also a user of
> SHM Bridge.

OK

Best regards,
Krzysztof