Re: [PATCH 1/7] dt-bindings: rtc: sun6i: Add Allwinner A733 support

[Jerome Brunet <jbrunet@baylibre.com>]

On sam. 28 mars 2026 at 20:37, Chen-Yu Tsai <wens@kernel.org> wrote:

> On Wed, Jan 21, 2026 at 7:03 PM Junhui Liu <junhui.liu@pigmoral.tech> wrote:
>>
>> The RTC module in the Allwinner A733 SoC is functionally compatible with
>> the sun6i RTC, but its internal Clock Control Unit (CCU) has significant
>> changes.
>>
>> The A733 supports selecting the oscillator between three frequencies:
>> 19.2MHz, 24MHz, and 26MHz. The RTC CCU relies on hardware to detect
>> which frequency is actually used on the board. By defining all three
>> frequencies as fixed-clocks in the device tree, the driver can identify
>> the hardware-detected frequency and expose it to the rest of the system.
>
> No. The board device tree shall have the exact and correct frequency
> defined in the external crystal device node. The operating system can
> use the hardware-detected frequency to "fix" the in-system representation
> if it is off.
>
>> Additionally, the A733 RTC CCU provides several new DCXO gate clocks for
>> specific modules, including SerDes, HDMI, and UFS.
>>
>> Signed-off-by: Junhui Liu <junhui.liu@pigmoral.tech>
>> ---
>>  .../bindings/rtc/allwinner,sun6i-a31-rtc.yaml      | 38 ++++++++++++++++++++--
>>  include/dt-bindings/clock/sun60i-a733-rtc.h        | 16 +++++++++
>>  2 files changed, 52 insertions(+), 2 deletions(-)
>>
>> diff --git a/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml b/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
>> index 9df5cdb6f63f..b18431955783 100644
>> --- a/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
>> +++ b/Documentation/devicetree/bindings/rtc/allwinner,sun6i-a31-rtc.yaml
>> @@ -26,6 +26,7 @@ properties:
>>            - allwinner,sun50i-h6-rtc
>>            - allwinner,sun50i-h616-rtc
>>            - allwinner,sun50i-r329-rtc
>> +          - allwinner,sun60i-a733-rtc
>>        - items:
>>            - const: allwinner,sun50i-a64-rtc
>>            - const: allwinner,sun8i-h3-rtc
>> @@ -46,11 +47,11 @@ properties:
>>
>>    clocks:
>>      minItems: 1
>> -    maxItems: 4
>> +    maxItems: 6
>>
>>    clock-names:
>>      minItems: 1
>> -    maxItems: 4
>> +    maxItems: 6
>>
>>    clock-output-names:
>>      minItems: 1
>> @@ -156,6 +157,38 @@ allOf:
>>          - clocks
>>          - clock-names
>>
>> +  - if:
>> +      properties:
>> +        compatible:
>> +          contains:
>> +            const: allwinner,sun60i-a733-rtc
>> +
>> +    then:
>> +      properties:
>> +        clocks:
>> +          minItems: 5
>> +          items:
>> +            - description: Bus clock for register access
>
>> +            - description: 19.2 MHz oscillator
>> +            - description: 24 MHz oscillator
>> +            - description: 26 MHz oscillator
>
> No. There is only one input. As in there is only one set of pins for the
> DCXO. The inputs are the same as on R329 / A523. Just use that list.
>
>> +            - description: AHB parent for internal SPI clock
>> +            - description: External 32768 Hz oscillator
>> +
>> +        clock-names:
>> +          minItems: 5
>> +          items:
>> +            - const: bus
>> +            - const: osc19M
>> +            - const: osc24M
>> +            - const: osc26M
>> +            - const: ahb
>> +            - const: ext-osc32k
>> +
>> +      required:
>> +        - clocks
>> +        - clock-names
>> +
>>    - if:
>>        properties:
>>          compatible:
>> @@ -164,6 +197,7 @@ allOf:
>>                - allwinner,sun8i-r40-rtc
>>                - allwinner,sun50i-h616-rtc
>>                - allwinner,sun50i-r329-rtc
>> +              - allwinner,sun60i-a733-rtc
>>
>>      then:
>>        properties:
>> diff --git a/include/dt-bindings/clock/sun60i-a733-rtc.h b/include/dt-bindings/clock/sun60i-a733-rtc.h
>> new file mode 100644
>> index 000000000000..8a2b5facad73
>> --- /dev/null
>> +++ b/include/dt-bindings/clock/sun60i-a733-rtc.h
>> @@ -0,0 +1,16 @@
>> +/* SPDX-License-Identifier: GPL-2.0-only OR MIT */
>> +
>> +#ifndef _DT_BINDINGS_CLK_SUN60I_A733_RTC_H_
>> +#define _DT_BINDINGS_CLK_SUN60I_A733_RTC_H_
>> +
>> +#define CLK_IOSC               0
>> +#define CLK_OSC32K             1
>> +#define CLK_HOSC               2
>
> The DCXO enable control has been present since at least the H6. We just
> never added it, as we would never disable it anyway.
>
> If you compare the RTC clock trees of the A733 and A523, the only addition
> besides the new gates seems to be the LOSC auto selection. But even that
> is just an illusion, as the A523 has the same registers for that.
>
> One could say the A733 RTC is almost backward compatible to the A523, if
> not for the two fastboot registers the A523 has at 0x120 and 0x124.
>
> So I ask that you try to integrate the differences into the existing
> driver and bindings. You can tweak and export internal clks if you
> need.

I'd like to help with that. I think it is doable but I have a question
regarding the binding of the existing driver, more precisely their usage
here:

https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/clk/sunxi-ng/ccu-sun6i-rtc.c?h=v7.1#n370

Clock indexes are supposed to be stable in DT (AFAIK) but with the code
linked the external 32k is at:

* "ext-32k" - so index 3 - if "clock-names" is present
* index 0 if clock names is not present

... but index 0 is supposed to be the bus clock according the binding
doc, whether "clock-names" is there or not :/

So what are those old r329 bindings ? is there a documentation defining
them somewhere ?

Cleaning that part would help with A733 addition in the existing driver
I think

>
>> +#define CLK_RTC_32K            3
>
> AFAICT besides being an internal clock, this is also fed to GPIO for
> debounce? We probably need to expose this on the A523 as well.
>
>
> Thanks
> ChenYu
>
>
>> +#define CLK_OSC32K_FANOUT      4
>> +#define CLK_HOSC_SERDES1       5
>> +#define CLK_HOSC_SERDES0       6
>> +#define CLK_HOSC_HDMI          7
>> +#define CLK_HOSC_UFS           8
>> +
>> +#endif /* _DT_BINDINGS_CLK_SUN60I_A733_RTC_H_ */
>>
>> --
>> 2.52.0
>>
>>

-- 
Jerome