linux-kernel - Re: [PATCH v4 4/4] dt-bindings: syscon: Add StarFive syscon doc

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Message-ID: <Y/3gxi8ZMWTrnCoe@wendy>
Date:   Tue, 28 Feb 2023 11:08:54 +0000
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Krzysztof Kozlowski <krzysztof.kozlowski@...aro.org>
CC:     William Qiu <william.qiu@...rfivetech.com>,
        Rob Herring <robh@...nel.org>,
        <linux-riscv@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        <linux-mmc@...r.kernel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Jaehoon Chung <jh80.chung@...sung.com>,
        Ulf Hansson <ulf.hansson@...aro.org>,
        <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4 4/4] dt-bindings: syscon: Add StarFive syscon doc

On Tue, Feb 28, 2023 at 11:37:20AM +0100, Krzysztof Kozlowski wrote:
> On 28/02/2023 10:05, William Qiu wrote:
> > On 2023/2/28 6:29, Rob Herring wrote:
> >> On Tue, Feb 21, 2023 at 10:44:02AM +0800, William Qiu wrote:
> >>> On 2023/2/21 7:43, Rob Herring wrote:
> >>>> On Wed, Feb 15, 2023 at 07:32:49PM +0800, William Qiu wrote:
> >>>>> Add documentation to describe StarFive System Controller Registers.
> >>>>>
> >>>>> Signed-off-by: William Qiu <william.qiu@...rfivetech.com>
> >>>>> ---
> >>>>>  .../bindings/soc/starfive/jh7110-syscon.yaml  | 51 +++++++++++++++++++
> >>>>>  MAINTAINERS                                   |  5 ++
> >>>>>  2 files changed, 56 insertions(+)
> >>>>>  create mode 100644 Documentation/devicetree/bindings/soc/starfive/jh7110-syscon.yaml
> >>>>>
> >>>>> diff --git a/Documentation/devicetree/bindings/soc/starfive/jh7110-syscon.yaml b/Documentation/devicetree/bindings/soc/starfive/jh7110-syscon.yaml
> >>>>> new file mode 100644
> >>>>> index 000000000000..fa4d8522a454
> >>>>> --- /dev/null
> >>>>> +++ b/Documentation/devicetree/bindings/soc/starfive/jh7110-syscon.yaml
> >>>>> @@ -0,0 +1,51 @@
> >>>>> +# SPDX-License-Identifier: (GPL-2.0 OR BSD-2-Clause)
> >>>>> +%YAML 1.2
> >>>>> +---
> >>>>> +$id: http://devicetree.org/schemas/soc/starfive/jh7110-syscon.yaml#
> >>>>> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >>>>> +
> >>>>> +title: StarFive JH7110 SoC system controller
> >>>>> +
> >>>>> +maintainers:
> >>>>> +  - William Qiu <william.qiu@...rfivetech.com>
> >>>>> +
> >>>>> +description: |
> >>>>> +  The StarFive JH7110 SoC system controller provides register information such
> >>>>> +  as offset, mask and shift to configure related modules such as MMC and PCIe.
> >>>>> +
> >>>>> +properties:
> >>>>> +  compatible:
> >>>>> +    items:
> >>>>> +      - enum:
> >>>>> +          - starfive,jh7110-stg-syscon
> >>>>> +          - starfive,jh7110-sys-syscon
> >>>>> +          - starfive,jh7110-aon-syscon
> >>>>
> >>>> Is 'syscon' really part of what the blocks are called? Is just 'stg', 
> >>>> 'sys' and 'aon' not unique enough?

> >>> In StarFive SoC, we do have syscrg/aoncrg/stgcrg, which is uesd to be the clock
> >>> controller, so 'syscon' is added to avoid confusion.
> >>
> >> You've only added to my confusion. 'syscrg' and 'sys-syscon' are 2 
> >> different h/w blocks and unrelated to each other? Or 'syscrg' is the 
> >> clock portion of 'sys-syscon'? In that case, 'syscrg' should be a child 
> >> of 'sys-syscon' or possibly just all one node. Please provide details on 
> >> the entire h/w block so we can provide better input on the bindings.

> > It's my description that's problematic.'syscon' here refers to the hardware module
> > inside our JH7110, which is different from the syscon interface in linux. The syscon
> > I added now uses the syscon interface of linux to read and write the syscon register
> > in our JH7110. So we decided to name it that way.
> 
> You didn't really answer Rob's questions.
> 
> Also, syscon is Linux term, so are you sure hardware module is called
> like this? Hardware engineers took pure Linux name and used it?

Their TRM uses the term SYSCON for these, yes.
Eg:
"The JH7110 system provides the following STG SYSCON control registers
which provides [sic] clock and reset signals to interfaces..."

In fact, the TRM I have describes the following system control register
blocks:
SYS CRG
STG CRG
AON CRG
SYS SYSCON
STG SYSCON
AON SYSCON
SYS IOMUX CFG
AON IOMUX CFG

My understanding is that the first 3 (the CRG ones) are concerned with
clocks and resets & the second 3 contain "random" configuration options,
such as their QSPI IP's configuration options, GPIO voltage settings
etc.

Each of these has a separate, 0x1000 aligned, block in the memory map.

Cheers,
Conor.


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