linux-kernel - Re: [PATCH RFC 05/14] dt-bindings/interrupt-controller: pdc: add SPI config register

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Date:   Fri, 20 Sep 2019 15:20:25 -0700
From:   Stephen Boyd <swboyd@...omium.org>
To:     Lina Iyer <ilina@...eaurora.org>
Cc:     Rob Herring <robh@...nel.org>, evgreen@...omium.org,
        linus.walleij@...aro.org, linux-kernel@...r.kernel.org,
        linux-arm-msm@...r.kernel.org, bjorn.andersson@...aro.org,
        mkshah@...eaurora.org, linux-gpio@...r.kernel.org,
        rnayak@...eaurora.org, devicetree@...r.kernel.org, maz@...nel.org,
        sibis@...eaurora.org
Subject: Re: [PATCH RFC 05/14] dt-bindings/interrupt-controller: pdc: add SPI config register

Quoting Lina Iyer (2019-09-17 14:50:20)
> On Fri, Sep 13 2019 at 13:53 -0600, Lina Iyer wrote:
> >On Thu, Sep 05 2019 at 18:03 -0600, Stephen Boyd wrote:
> >>Quoting Lina Iyer (2019-09-03 10:07:22)
> >>>On Mon, Sep 02 2019 at 07:58 -0600, Marc Zyngier wrote:
> >>>>On 02/09/2019 14:38, Rob Herring wrote:
> >>>>> On Thu, Aug 29, 2019 at 12:11:54PM -0600, Lina Iyer wrote:
> >>>These are not GIC registers but located on the PDC interface to the GIC.
> >>>They may or may not be secure access controlled, depending on the SoC.
> >>>
> >>
> >>It looks like it falls under this "mailbox" device which is really the
> >>catch all bucket for bits with no home besides they're related to the
> >>apps CPUs/subsystem.
> >>
> >Thanks for pointing to this.
> >>      apss_shared: mailbox@...90000 {
> >>              compatible = "qcom,sdm845-apss-shared";
> >>              reg = <0 0x17990000 0 0x1000>;
> >But this doesn't seem correct. The registers in this page are all not
> >mailbox door bell registers. We should restrict the space allocated to
> >the mbox to 0xC or something, definitely, not the whole page. They all
> >cannot be treated as a mailbox registers.

Well the binding is already done and this is the compatible string for
this node and register region. Sounds like this node is a mailbox plus
some more stuff in the same page.

> >>              #mbox-cells = <1>;
> >>      };
> >>
> >>Can you point to this node with a phandle and then parse the reg
> >>property out of it to use in the scm readl/writel APIs? Maybe it can be
> >>a two cell property with <&apps_shared 0xf0> to indicate the offset to
> >>the registers to read/write? In non-secure mode presumably we need to
> >>also write these registers? Good news is that there's a regmap for this
> >>driver already, so maybe that can be acquired from the pdc driver.
> >>
> >The register space collection seems to be mix of different types of
> >application processor registers that should probably not be grouped up
> >under one subsystem. A single regmap doesn't seem correct either.

Why isn't a single regmap correct? The PDC driver should be able to use
it to read/write into this register space. The lock on the regmap will
need to be changed to a raw lock though for RT. Otherwise it looks OK to
me.