linux-kernel - Re: [PATCH v5 08/10] interconnect: qcom: msm8996: Specify no bus clock scaling on A0NoC

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Date:   Thu, 23 Feb 2023 06:07:10 -0800
From:   Bjorn Andersson <andersson@...nel.org>
To:     Konrad Dybcio <konrad.dybcio@...aro.org>
Cc:     Dmitry Baryshkov <dmitry.baryshkov@...aro.org>,
        Andy Gross <agross@...nel.org>,
        Georgi Djakov <djakov@...nel.org>,
        Evan Green <evgreen@...omium.org>,
        Jun Nie <jun.nie@...aro.org>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Brian Masney <masneyb@...tation.org>,
        Yassine Oudjana <y.oudjana@...tonmail.com>,
        Georgi Djakov <georgi.djakov@...aro.org>,
        Bryan O'Donoghue <bryan.odonoghue@...aro.org>,
        linux-arm-msm@...r.kernel.org, linux-pm@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/10] interconnect: qcom: msm8996: Specify no bus
 clock scaling on A0NoC

On Fri, Feb 17, 2023 at 09:28:54PM +0100, Konrad Dybcio wrote:
> 
> 
> On 17.02.2023 21:26, Dmitry Baryshkov wrote:
> > On Fri, 17 Feb 2023 at 21:53, Konrad Dybcio <konrad.dybcio@...aro.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@...aro.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

Why not let go of this "convenience" and have num_clocks actually mean
number of clocks?

Regards,
Bjorn

> <0 => consider there's zero
> 
> ..but maybe that's just me.. if you don't find it ugly, I may just
> go with that.
> 
> Konrad
> > 
> >>
> >> Konrad
> >>>
> >>> Konrad
> >>>>  drivers/interconnect/qcom/msm8996.c | 1 +
> >>>>  1 file changed, 1 insertion(+)
> >>>>
> >>>> diff --git a/drivers/interconnect/qcom/msm8996.c b/drivers/interconnect/qcom/msm8996.c
> >>>> index 1a5e0ad36cc4..45eb8675fb11 100644
> >>>> --- a/drivers/interconnect/qcom/msm8996.c
> >>>> +++ b/drivers/interconnect/qcom/msm8996.c
> >>>> @@ -1817,6 +1817,7 @@ static const struct qcom_icc_desc msm8996_a0noc = {
> >>>>      .type = QCOM_ICC_NOC,
> >>>>      .nodes = a0noc_nodes,
> >>>>      .num_nodes = ARRAY_SIZE(a0noc_nodes),
> >>>> +    .num_bus_clocks = -1, /* No bus clock scaling */
> >>>>      .intf_clocks = a0noc_intf_clocks,
> >>>>      .num_intf_clocks = ARRAY_SIZE(a0noc_intf_clocks),
> >>>>      .has_bus_pd = true,
> >>>>
> > 
> > 
> >