linux-kernel - Re: [PATCH v7 6/9] interconnect: qcom: rpm: Handle interface clocks

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Message-ID: <6d10906e-08cd-0380-5f5d-3ac0eec60276@linaro.org>
Date:   Fri, 10 Mar 2023 15:26:35 +0100
From:   Konrad Dybcio <konrad.dybcio@...aro.org>
To:     Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Georgi Djakov <djakov@...nel.org>,
        Dmitry Baryshkov <dmitry.baryshkov@...aro.org>
Cc:     linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v7 6/9] interconnect: qcom: rpm: Handle interface clocks



On 10.03.2023 15:21, Bryan O'Donoghue wrote:
> On 08/03/2023 21:40, Konrad Dybcio wrote:
>> Some (but not all) providers (or their specific nodes) require
>> specific clocks to be turned on before they can be accessed. Failure
>> to ensure that results in a seemingly random system crash (which
>> would usually happen at boot with the interconnect driver built-in),
>> resulting in the platform not booting up properly.
> 
> Can you give an example of which clocks on which SoC's ?
See for example 67fb53745e0b

This was a clock documented downstream under the node-qos clocks here:

https://github.com/sonyxperiadev/kernel/blob/aosp/LA.UM.5.7.r1/arch/arm/boot/dts/qcom/msm8996-bus.dtsi#L102-L109

but there are occasions where such clocks are undocumented and downstream
skips them because it relies on them being on by miracle, such as the case
of MASTER_IPA and the IPA rpmcc clock on msm8998. Downstream has no
sync_state, so they would only set the QoS registers when the relevant
hardware was online, so the clocks were on already.

> 
> Is the intention of this patch to subsequently go through *.dts *.dtsi and start to remove assigned-clocks ?
> 
> Are we saying that currently there ought to be assigned-clocks for some of these NoC declarations ?
Not really, assigned-clocks are used for static ratesetting, see
for example dwc3 nodes where we need it to be fast enough for
HS/SS operation at all times (though that should have prooobably
been handled in the driver but it's a separate topic), I don't
think any of them were used to combat what this commit tries to.

Konrad
> 
> ---
> bod