Hi Claudiu, > -----Original Message----- > From: claudiu beznea <claudiu.beznea@xxxxxxxxx> > Sent: Tuesday, September 3, 2024 8:44 AM > Subject: Re: [PATCH v3 01/12] dt-bindings: clock: renesas,r9a08g045-vbattb: Document VBATTB > > > > On 03.09.2024 10:36, Biju Das wrote: > > Hi Claudiu, > > > >> -----Original Message----- > >> From: claudiu beznea <claudiu.beznea@xxxxxxxxx> > >> Sent: Tuesday, September 3, 2024 8:28 AM > >> Subject: Re: [PATCH v3 01/12] dt-bindings: clock: > >> renesas,r9a08g045-vbattb: Document VBATTB > >> > >> > >> > >> On 03.09.2024 09:58, Biju Das wrote: > >>> Hi Claudiu, > >>> > >>>> -----Original Message----- > >>>> From: Claudiu <claudiu.beznea@xxxxxxxxx> > >>>> Sent: Friday, August 30, 2024 2:02 PM > >>>> Subject: [PATCH v3 01/12] dt-bindings: clock: > >>>> renesas,r9a08g045-vbattb: Document VBATTB > >>>> > >>>> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx> > >>>> > >>>> 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@xxxxxxxxxxxxxx> > >>>> --- > >>>> > >>>> 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.ya > >>>> ml > >>>> > >>>> diff --git > >>>> a/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb. > >>>> ya > >>>> ml > >>>> b/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vbattb. > >>>> ya > >>>> ml > >>>> new file mode 100644 > >>>> index 000000000000..29df0e01fae5 > >>>> --- /dev/null > >>>> +++ b/Documentation/devicetree/bindings/clock/renesas,r9a08g045-vba > >>>> +++ tt > >>>> +++ b.y > >>>> +++ aml > >>>> @@ -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@xxxxxxxxxxxxxx> > >>>> + > >>>> +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 > >>> > >>> Not sure, you need to document "PD_VBATT" power domain as per Table > >>> 41.2, this LSI supports 3 power domains(PD_ISOVCC, PD_VCC, PD_VBATT) > >>> > >>> Power Mode PD_ISOVCC PD_VCC PD_VBATT > >>> ALL_ON ON ON ON > >>> AWO OFF ON ON > >>> VBATT OFF OFF ON > >>> ALL_OFF OFF OFF OFF > >>> > >>> PD_VBATT domain is the area where the RTC/backup register is > >>> located, works on battery power when the power of PD_VCC and PD_ISOVCC domain are turned off. > >> > >> In Linux, the CPG is the power domain provider for all the IPs in > >> RZ/G3S SoC (modeled though MSTOP CPG support). This is how it is currently implemented. > >> > >> Then groups of IPs are part of power domains PD_ISOVCC, PD_VCC, PD_VBATT. > >> These power domains are i2c controlled with the help of firmware (at least at the moment). > >> > >> From HW manual: > >> - PD_VCC domain always powered on area. > >> > >> - PD_ISOVCC domain is the area where the power can be turned off. > >> > >> - PD_VBATT domain is the area where the RTC/backup register is located, > >> works on battery power when the power of . > >> > >> The power to these domains are controlled with the help of firmware. > >> Linux cannot do control itself as the CPU is in the PD_ISOVCC. If you > >> look at picture 41.3 Power mode transition [1] it is mentioned the > >> relation b/w these power domains (controlled by PMIC though firmware) > >> and the supported power saving > >> modes: ALL_ON, AWO, VBATT. > >> > > > > DT describes hardware. So, the question was, from that perspective, do > > we need to document PD_VBATT domain, as it can be controlled outside linux?? > > The control to these domains is passed to firmware. > > From my point of view these will never be used by Linux becuase: > - the PD_ISOVCC is where the CPU resides and it cannot cut itself its power > - the PD_VCC is a domain where critical IPs like CPG, SYSC resides > - the VBATT is where the RTC resides, RTC that should stay on forever > > Should we document something that will be never used? If it is inside the system, you are describing to avoid ABI breakages any future. Eg [1], there are interrupts we documented, Don't know we will ever use it in linux. [1] https://git.kernel.org/pub/scm/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/soc/renesas/renesas,rzg2l-sysc.yaml#n58 Cheers, Biju
