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

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Date:   Fri, 13 Sep 2019 13:53:26 -0600
From:   Lina Iyer <ilina@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.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
Subject: Re: [PATCH RFC 05/14] dt-bindings/interrupt-controller: pdc: add SPI
 config register

Sorry, I couldn't get to this earlier.

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.
>		#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.

-- Lina