linux-kernel - Re: [PATCH v5 1/3] dt-bindings: reset: microchip sparx5 reset driver bindings

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Message-ID: <f4d3c144326ce2984acfbc0e4b04c7f3edd6c4e8.camel@microchip.com>
Date:   Tue, 16 Feb 2021 09:32:28 +0100
From:   Steen Hegelund <steen.hegelund@...rochip.com>
To:     Alexandre Belloni <alexandre.belloni@...tlin.com>
CC:     Philipp Zabel <p.zabel@...gutronix.de>,
        Rob Herring <robh+dt@...nel.org>, Andrew Lunn <andrew@...n.ch>,
        Microchip Linux Driver Support <UNGLinuxDriver@...rochip.com>,
        Gregory Clement <gregory.clement@...tlin.com>,
        <linux-kernel@...r.kernel.org>,
        <linux-arm-kernel@...ts.infradead.org>,
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH v5 1/3] dt-bindings: reset: microchip sparx5 reset
 driver bindings

Hi Alex,

On Mon, 2021-02-15 at 18:32 +0100, Alexandre Belloni wrote:
> EXTERNAL EMAIL: Do not click links or open attachments unless you
> know the content is safe
> 
> On 10/02/2021 10:19:50+0100, Steen Hegelund wrote:
> > Document the Sparx5 reset device driver bindings
> > 
> > The driver uses two IO ranges on sparx5 for access to
> > the reset control and the reset status.
> > 
> > Signed-off-by: Steen Hegelund <steen.hegelund@...rochip.com>
> > ---
> >  .../bindings/reset/microchip,rst.yaml         | 55
> > +++++++++++++++++++
> >  1 file changed, 55 insertions(+)
> >  create mode 100644
> > Documentation/devicetree/bindings/reset/microchip,rst.yaml
> > 
> > diff --git
> > a/Documentation/devicetree/bindings/reset/microchip,rst.yaml
> > b/Documentation/devicetree/bindings/reset/microchip,rst.yaml
> > new file mode 100644
> > index 000000000000..80046172c9f8
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/reset/microchip,rst.yaml
> > @@ -0,0 +1,55 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: "http://devicetree.org/schemas/reset/microchip,rst.yaml#"
> > +$schema: "http://devicetree.org/meta-schemas/core.yaml#"
> > +
> > +title: Microchip Sparx5 Switch Reset Controller
> > +
> > +maintainers:
> > +  - Steen Hegelund <steen.hegelund@...rochip.com>
> > +  - Lars Povlsen <lars.povlsen@...rochip.com>
> > +
> > +description: |
> > +  The Microchip Sparx5 Switch provides reset control and
> > implements the following
> > +  functions
> > +    - One Time Switch Core Reset (Soft Reset)
> > +
> > +properties:
> > +  $nodename:
> > +    pattern: "^reset-controller@[0-9a-f]+$"
> > +
> > +  compatible:
> > +    const: microchip,sparx5-switch-reset
> > +
> > +  reg:
> > +    items:
> > +      - description: cpu block registers
> > +      - description: global control block registers
> > +
> > +  reg-names:
> > +    items:
> > +      - const: cpu
> > +      - const: gcb
> > +
> 
> I still think this is not right because then you will be mapping the
> same set of register using multiple drivers without any form of
> synchronisation which will work because you are mapping the region
> without requesting it. But this may lead to issues later.
> 
> At least, you should make cpu start at 0x80 and of size 4. Else, you
> won't be able to define and use the GPRs that are in front of
> CPU_REGS:RESET.
> 
> I would still keep DEVCPU_GCB:CHIP_REGS as a syscon, especially since
> you are mapping the whole set of registers.

Ok.  I will use a syscon for the General Control Block and a very small
range for the CPU Reset register, to minimize the register footprint.

> 
> 
> > +  "#reset-cells":
> > +    const: 1
> > +
> > +required:
> > +  - compatible
> > +  - reg
> > +  - reg-names
> > +  - "#reset-cells"
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > +  - |
> > +    reset: reset-controller@0 {
> > +        compatible = "microchip,sparx5-switch-reset";
> > +        #reset-cells = <1>;
> > +        reg = <0x0 0xd0>,
> > +              <0x11010000 0x10000>;
> > +        reg-names = "cpu", "gcb";
> > +    };
> > +
> > --
> > 2.30.0
> > 
> 
> --
> Alexandre Belloni, Bootlin
> Embedded Linux and Kernel engineering
> https://bootlin.com


Thanks for your comments


-- 
BR
Steen

-=-=-=-=-=-=-=-=-=-=-=-=-=-=
steen.hegelund@...rochip.com