Message-ID: <ad231bd5-4308-4a69-86c5-5431eba2807d@linaro.org>
Date:   Sat, 18 Feb 2023 00:19:34 +0200
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Subject: Re: [PATCH v5 08/10] interconnect: qcom: msm8996: Specify no bus
 clock scaling on A0NoC
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To:     Konrad Dybcio <konrad.dybcio@linaro.org>
Cc:     Andy Gross <agross@kernel.org>,
        Bjorn Andersson <andersson@kernel.org>,
        Georgi Djakov <djakov@kernel.org>,
        Evan Green <evgreen@chromium.org>,
        Jun Nie <jun.nie@linaro.org>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Brian Masney <masneyb@onstation.org>,
        Yassine Oudjana <y.oudjana@protonmail.com>,
        Georgi Djakov <georgi.djakov@linaro.org>,
        Bryan O'Donoghue <bryan.odonoghue@linaro.org>,
        linux-arm-msm@vger.kernel.org, linux-pm@vger.kernel.org,
        linux-kernel@vger.kernel.org
References: <20230217-topic-icc-fixes-v5-v5-0-c9a550f9fdb9@linaro.org>
 <20230217-topic-icc-fixes-v5-v5-8-c9a550f9fdb9@linaro.org>
 <8c4f1cc8-c1f8-06b6-53fe-7507d74ca958@linaro.org>
 <3c205131-632a-6592-5dc0-82313b26e5f6@linaro.org>
 <CAA8EJprJYPAsFZgu-DwjOHm6FsUEJ309zDo=Muh04L4B4oWhmw@mail.gmail.com>
 <5a2f502a-6530-dc8c-a81e-3d2a33964366@linaro.org>
From:   Dmitry Baryshkov <dmitry.baryshkov@linaro.org>
In-Reply-To: <5a2f502a-6530-dc8c-a81e-3d2a33964366@linaro.org>
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On 17/02/2023 22:28, Konrad Dybcio wrote:
> 
> 
> On 17.02.2023 21:26, Dmitry Baryshkov wrote:
>> On Fri, 17 Feb 2023 at 21:53, Konrad Dybcio <konrad.dybcio@linaro.org> wrote:
>>>
>>>
>>>
>>> On 17.02.2023 20:27, Konrad Dybcio wrote:
>>>>
>>>>
>>>> On 17.02.2023 11:46, Konrad Dybcio wrote:
>>>>> A0NoC only does bus scaling through RPM votes and does not have any
>>>>> ICC clocks. Describe this.
>>>>>
>>>>> Signed-off-by: Konrad Dybcio <konrad.dybcio@linaro.org>
>>>>> ---
>>>> This is bad, as devm_clk_get_bulk{"", _optional} doesn't
>>>> check if num_clocks makes sense and passes "-1" down the
>>>> devres alloc chain..
>>>>
>>>> I'll rework this for the next revision by simply assigning
>>>> the common "bus", "bus_a" set everywhere instead of relying
>>>> on it being there by default..
>>> Or maybe I shouldn't, as that will require redefining the array
>>> over and over again.. Perhaps just passing <&xo_board>, <&xo_board>
>>> to a0noc's "bus", "bus_a", similar to what's been done on SDM630's
>>> GNoC would be less messy?
>>
>> What about simply skipping a call to devm_clk_get if num_bus_clocks is negative?
> I tested that locally before reporting the mistake on my side and
> while it works, I just consider it.. ugly, because:
> 
> num_clocks =
>> 0 => use the externally specified num_/clocks (logical)
> =0 => use the default 2
> <0 => consider there's zero
> 
> ..but maybe that's just me.. if you don't find it ugly, I may just
> go with that.

Would 'lesser ugliness' count? Maybe add a define 'ICC_RPM_NO_CLOCKS = 
-1'? I think that spawning default bus & bus_a everywhere would be worse.

When this driver is rewritten in Rust, we'll have a clear distinction 
between None (meaning default two clocks) and Some(0) (meaning no 
clocks). Wait, does that sound even more ugly?

-- 
With best wishes
Dmitry