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

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Date:   Mon, 23 Sep 2019 11:41:20 +0530
From:   Sibi Sankar <sibis@...eaurora.org>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Lina Iyer <ilina@...eaurora.org>, 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,
        linux-arm-msm-owner@...r.kernel.org
Subject: Re: [PATCH RFC 05/14] dt-bindings/interrupt-controller: pdc: add SPI
 config register

On 2019-09-21 03:50, Stephen Boyd wrote:
> 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.
> 

Bjorn already noticed ^^ during the
original review. Hence the compatible
was correctly named "apss-shared"
instead of following the older bindings.

>> >>              #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.

-- 
-- Sibi Sankar --
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project.