linux-kernel - Re: [PATCH 02/12] dt-bindings: clock: renesas,rzg3s-vbattb-clk: Document the VBATTB clock driver

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Date: Mon, 17 Jun 2024 16:19:30 +0100
From: Conor Dooley <conor@...nel.org>
To: claudiu beznea <claudiu.beznea@...on.dev>
Cc: geert+renesas@...der.be, mturquette@...libre.com, sboyd@...nel.org,
	robh@...nel.org, krzk+dt@...nel.org, conor+dt@...nel.org,
	lee@...nel.org, alexandre.belloni@...tlin.com,
	magnus.damm@...il.com, linux-renesas-soc@...r.kernel.org,
	linux-clk@...r.kernel.org, devicetree@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-rtc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: Re: [PATCH 02/12] dt-bindings: clock: renesas,rzg3s-vbattb-clk:
 Document the VBATTB clock driver

On Mon, Jun 17, 2024 at 10:02:47AM +0300, claudiu beznea wrote:
> 
> 
> On 15.06.2024 15:17, Conor Dooley wrote:
> > On Fri, Jun 14, 2024 at 10:19:22AM +0300, Claudiu wrote:
> >> From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >>
> >> The VBATTB IP of the Renesas RZ/G3S SoC controls the clock that feeds
> >> the RTC and the tamper detector. Add documentation for the VBATTB clock
> >> driver.
> >>
> >> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >> ---
> >>  .../clock/renesas,rzg3s-vbattb-clk.yaml       | 90 +++++++++++++++++++
> >>  1 file changed, 90 insertions(+)
> >>  create mode 100644 Documentation/devicetree/bindings/clock/renesas,rzg3s-vbattb-clk.yaml
> >>
> >> diff --git a/Documentation/devicetree/bindings/clock/renesas,rzg3s-vbattb-clk.yaml b/Documentation/devicetree/bindings/clock/renesas,rzg3s-vbattb-clk.yaml
> >> new file mode 100644
> >> index 000000000000..ef52a0c0f874
> >> --- /dev/null
> >> +++ b/Documentation/devicetree/bindings/clock/renesas,rzg3s-vbattb-clk.yaml
> >> @@ -0,0 +1,90 @@
> >> +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> >> +%YAML 1.2
> >> +---
> >> +$id: http://devicetree.org/schemas/clock/renesas,rzg3s-vbattb-clk.yaml#
> >> +$schema: http://devicetree.org/meta-schemas/core.yaml#
> >> +
> >> +title: Renesas VBATTB clock
> >> +
> >> +maintainers:
> >> +  - Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
> >> +
> >> +description:
> >> +  Renesas VBATTB module is an always on powered module (backed by battery) which
> >> +  generates a clock (VBATTCLK). This clocks feeds the RTC and the tamper detector
> >> +  modules.
> >> +
> >> +properties:
> >> +  compatible:
> >> +    const: renesas,rzg3s-vbattb-clk
> >> +
> >> +  reg:
> >> +    maxItems: 1
> >> +
> >> +  clocks:
> >> +    items:
> >> +      - description: VBATTB module clock
> >> +      - description: VBATTB input xtal
> >> +
> >> +  clock-names:
> >> +    items:
> >> +      - const: bclk
> >> +      - const: vbattb_xtal
> >> +
> >> +  '#clock-cells':
> >> +    const: 0
> >> +
> >> +  power-domains:
> >> +    maxItems: 1
> >> +
> >> +  renesas,vbattb-load-nanofarads:
> >> +    description: load capacitance of the on board xtal
> >> +    $ref: /schemas/types.yaml#/definitions/uint32
> >> +    enum: [ 4000, 7000, 9000, 12500 ]
> >> +
> >> +  renesas,vbattb-osc-bypass:
> >> +    description: set when external clock is connected to RTXOUT pin
> >> +    type: boolean
> > 
> > When you say "external clock", is that an input or an output?
> 
> I took that statement from the HW manual. As of the HW manual [1], table
> 42.2, that would be an input.

Forgive me for not wanting to open the zip etc and find the information
in the document, but why do you need an extra property? Is it not
something you can determine from the clocks/clock-names properties?
It sounds like an additional clock from your description, is it actually
different way to provide the second clock you mention above?

> 
> [1]
> https://www.renesas.com/us/en/products/microcontrollers-microprocessors/rz-mpus/rzg3s-general-purpose-microprocessors-single-core-arm-cortex-a55-11-ghz-cpu-and-dual-core-cortex-m33-250
> 

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