linux-kernel - Re: [PATCH V3 3/3] mailbox: qcom-apcs: Add SM6125 compatible

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Message-ID: <CABb+yY2wy4iSKjn+SihQ=FE=YwcEzUNOpGw_CV22Anzgbba8hA@mail.gmail.com>
Date:   Mon, 21 Jun 2021 20:00:14 -0500
From:   Jassi Brar <jassisinghbrar@...il.com>
To:     Bjorn Andersson <bjorn.andersson@...aro.org>
Cc:     Rob Herring <robh+dt@...nel.org>,
        Martin Botka <martin.botka@...ainline.org>,
        ~postmarketos/upstreaming@...ts.sr.ht,
        Konrad Dybcio <konrad.dybcio@...ainline.org>,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@...ainline.org>,
        Marijn Suijten <marijn.suijten@...ainline.org>,
        jamipkettunen@...ainline.org, Andy Gross <agross@...nel.org>,
        linux-arm-msm <linux-arm-msm@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V3 3/3] mailbox: qcom-apcs: Add SM6125 compatible

On Mon, Jun 21, 2021 at 6:35 PM Bjorn Andersson
<bjorn.andersson@...aro.org> wrote:
>
> On Mon 21 Jun 18:19 CDT 2021, Rob Herring wrote:
>
> > On Mon, Jun 21, 2021 at 5:10 PM Jassi Brar <jassisinghbrar@...il.com> wrote:
> > >
> > > On Mon, Jun 21, 2021 at 2:46 PM Rob Herring <robh+dt@...nel.org> wrote:
> > > >
> > > > On Sun, Jun 20, 2021 at 10:03 PM Jassi Brar <jassisinghbrar@...il.com> wrote:
> > > > >
> > > > > On Sat, Jun 12, 2021 at 4:46 AM Martin Botka
> > > > > <martin.botka@...ainline.org> wrote:
> > > > > >
> > > > > > This commit adds compatible for the SM6125 SoC
> > > > > >
> > > > > > Signed-off-by: Martin Botka <martin.botka@...ainline.org>
> > > > > > ---
> > > > > > Changes in V2:
> > > > > > None
> > > > > > Changes in V3:
> > > > > > Change compatible to apcs-hmss-global
> > > > > >  drivers/mailbox/qcom-apcs-ipc-mailbox.c | 5 +++++
> > > > > >  1 file changed, 5 insertions(+)
> > > > > >
> > > > > > diff --git a/drivers/mailbox/qcom-apcs-ipc-mailbox.c b/drivers/mailbox/qcom-apcs-ipc-mailbox.c
> > > > > > index f25324d03842..f24c5ad8d658 100644
> > > > > > --- a/drivers/mailbox/qcom-apcs-ipc-mailbox.c
> > > > > > +++ b/drivers/mailbox/qcom-apcs-ipc-mailbox.c
> > > > > > @@ -57,6 +57,10 @@ static const struct qcom_apcs_ipc_data sdm660_apcs_data = {
> > > > > >         .offset = 8, .clk_name = NULL
> > > > > >  };
> > > > > >
> > > > > > +static const struct qcom_apcs_ipc_data sm6125_apcs_data = {
> > > > > > +       .offset = 8, .clk_name = NULL
> > > > > > +};
> > > > > > +
> > > > > >  static const struct qcom_apcs_ipc_data apps_shared_apcs_data = {
> > > > > >         .offset = 12, .clk_name = NULL
> > > > > >  };
> > > > > > @@ -166,6 +170,7 @@ static const struct of_device_id qcom_apcs_ipc_of_match[] = {
> > > > > >         { .compatible = "qcom,sc8180x-apss-shared", .data = &apps_shared_apcs_data },
> > > > > >         { .compatible = "qcom,sdm660-apcs-hmss-global", .data = &sdm660_apcs_data },
> > > > > >         { .compatible = "qcom,sdm845-apss-shared", .data = &apps_shared_apcs_data },
> > > > > > +       { .compatible = "qcom,sm6125-apcs-hmss-global", .data = &sm6125_apcs_data },
> > > > > >         { .compatible = "qcom,sm8150-apss-shared", .data = &apps_shared_apcs_data },
> > > > > >         { .compatible = "qcom,sdx55-apcs-gcc", .data = &sdx55_apcs_data },
> > > > > >         {}
> > > > > >
> > > > > These all are basically different names for the same controller.
> > > > > The 'offset' is a configuration parameter and the 'clock', when NULL,
> > > > > is basically some "always-on" clock.
> > > > > I am sure we wouldn't be doing it, if the controller was third-party.
> > > >
> > > > If newer implementations are 'the same', then they should have a
> > > > fallback compatible to the existing one that is the same and no driver
> > > > change is needed. If the differences are board or instance (within an
> > > > SoC) specific, then a DT property would be appropriate.
> > > >
> > > The controllers (13 now) only differ by the 'offset' where the
> > > registers are mapped. Clock-name is a pure s/w artifact.
> > > So, maybe we could push all these in DT.
> >
> > Why is 'reg' not used for the offset?
> >
>
> The DT node and its "reg" describes the whole IP block.
>
> The particular register that we care of has, as you can see, moved
> around during the various platforms and some incarnations of this IP
> block provides controls for CPU-related clocks as well.
>
> We can certainly have the multiple compatible points to the same
> apcs_data, but I'm not able to spot a reasonable "catch-all compatible"
> given that I don't see any natural groupings.
>
Any platform that comes later may reuse the already available compatible.
For example drop this patch and reuse "qcom,sdm660-apcs-hmss-global" ?

> > In any case, we can't really get rid of the first 13 instances though...
> >
>
> Right, we have the problem that we have DTBs out there that relies on
> these compatibles, but as Jassi requests we'd have to start describing
> the internal register layout in DT - which this binding purposefully
> avoids.
>
Not these strings, but 'offset' and 'clock-name' as optional
properties that new platforms can use.

cheers.