Re: [PATCH v3 01/12] dt-bindings: clock: renesas,r9a08g045-vbattb: Document VBATTB

Alexandre Belloni
2024-08-30T22:06:53Z

On 30/08/2024 12:46:33-0500, Rob Herring wrote:
> On Fri, Aug 30, 2024 at 04:02:07PM +0300, Claudiu wrote:
> > From: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> >
> > The VBATTB IP of the Renesas RZ/G3S SoC controls the clock for RTC,
> > the tamper detector and a small general usage memory of 128B. Add
> > documentation for it.
> >
> > Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> > ---
> >
> > Changes in v3:
> > - moved the file to clock dt bindings directory as it is the
> > only functionality supported at the moment; the other functionalities
> > (tamper detector, SRAM) are offered though register spreaded
> > though the address space of the VBATTB IP and not actually
> > individual devices; the other functionalities are not
> > planned to be supported soon and if they will be I think they
> > fit better on auxiliary bus than MFD
> > - dropped interrupt names as requested in the review process
> > - dropped the inner node for clock controller
> > - added #clock-cells
> > - added rtx clock
> > - updated description for renesas,vbattb-load-nanofarads
> > - included dt-bindings/interrupt-controller/irq.h in examples section
> >
> > Changes in v2:
> > - changed file name and compatible
> > - updated title, description sections
> > - added clock controller part documentation and drop dedicated file
> > for it included in v1
> > - used items to describe interrupts, interrupt-names, clocks, clock-names,
> > resets
> > - dropped node labels and status
> > - updated clock-names for clock controller to cope with the new
> > logic on detecting the necessity to setup bypass
> >
> > .../clock/renesas,r9a08g045-vbattb.yaml | 81 +++++++++++++++++++
> > 1 file changed, 81 insertions(+)
> > create mode 100644 Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb.yaml
> >
> > diff --git a/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb.yaml b/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb.yaml
> > new file mode 100644
> > index 000000000000..29df0e01fae5
> > --- /dev/null
> > +++ b/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb.yaml
> > @@ -0,0 +1,81 @@
> > +# SPDX-License-Identifier: (GPL-2.0-only OR BSD-2-Clause)
> > +%YAML 1.2
> > +---
> > +$id: http://devicetree.org/schemas/clock/renesas,r9a08g045-vbattb.yaml#
> > +$schema: http://devicetree.org/meta-schemas/core.yaml#
> > +
> > +title: Renesas Battery Backup Function (VBATTB)
> > +
> > +description:
> > + Renesas VBATTB is an always on powered module (backed by battery) which
> > + controls the RTC clock (VBATTCLK), tamper detection logic and a small
> > + general usage memory (128B).
> > +
> > +maintainers:
> > + - Claudiu Beznea <claudiu.beznea.uj@bp.renesas.com>
> > +
> > +properties:
> > + compatible:
> > + const: renesas,r9a08g045-vbattb
> > +
> > + reg:
> > + maxItems: 1
> > +
> > + interrupts:
> > + items:
> > + - description: tamper detector interrupt
> > +
> > + clocks:
> > + items:
> > + - description: VBATTB module clock
> > + - description: RTC input clock (crystal oscillator or external clock device)
> > +
> > + clock-names:
> > + items:
> > + - const: bclk
> > + - const: rtx
> > +
> > + '#clock-cells':
> > + const: 1
> > +
> > + power-domains:
> > + maxItems: 1
> > +
> > + resets:
> > + items:
> > + - description: VBATTB module reset
> > +
> > + renesas,vbattb-load-nanofarads:
>
> Use defined units, don't add your own. So -picofarads should work for
> you.

We have a generic quartz-load-femtofarads property for RTCs which is
what you define because the driver has VBATTB_XOSCCR_XSEL_4_PF which I
guess is 4 pF which is 0.004 nF and 4000 fF.

>
> > + description: load capacitance of the on board crystal oscillator
> > + $ref: /schemas/types.yaml#/definitions/uint32
> > + enum: [ 4000, 7000, 9000, 12500 ]
> > +
> > +required:
> > + - compatible
> > + - reg
> > + - interrupts
> > + - clocks
> > + - clock-names
> > + - '#clock-cells'
> > + - power-domains
> > + - resets
> > +
> > +additionalProperties: false
> > +
> > +examples:
> > + - |
> > + #include <dt-bindings/clock/r9a08g045-cpg.h>
> > + #include <dt-bindings/interrupt-controller/arm-gic.h>
> > + #include <dt-bindings/interrupt-controller/irq.h>
> > +
> > + vbattb@1005c000 {
>
> clock-controller@...
>
> > + compatible = "renesas,r9a08g045-vbattb";
> > + reg = <0x1005c000 0x1000>;
> > + interrupts = <GIC_SPI 43 IRQ_TYPE_LEVEL_HIGH>;
> > + clocks = <&cpg CPG_MOD R9A08G045_VBAT_BCLK>, <&vbattb_xtal>;
> > + clock-names = "bclk", "rtx";
> > + #clock-cells = <1>;
> > + power-domains = <&cpg>;
> > + resets = <&cpg R9A08G045_VBAT_BRESETN>;
> > + renesas,vbattb-load-nanofarads = <12500>;
> > + };
> > --
> > 2.39.2
> >

--
Alexandre Belloni, co-owner and COO, Bootlin
Embedded Linux and Kernel engineering