Hi, Geert, Krzysztof,
On 31.10.2024 10:43, Geert Uytterhoeven wrote:
> Hi Krzysztof,
>
> On Thu, Oct 31, 2024 at 8:48 AM Krzysztof Kozlowski <krzk@xxxxxxxxxx> wrote:
>> On Wed, Oct 30, 2024 at 01:01:13PM +0200, Claudiu wrote:
>>> From: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>>>
>>> The VBATTB IP of the Renesas RZ/G3S SoC controls the clock that is used
>>> by the RTC. The input to the VBATTB could be a 32KHz crystal
>>> or an external clock device.
>>>
>>> The HW block diagram for the clock generator is as follows:
>>>
>>> +----------+ XC `\
>>> RTXIN --->| |----->| \ +----+ VBATTCLK
>>> | 32K clock| | |----->|gate|----------->
>>> | osc | XBYP | | +----+
>>> RTXOUT --->| |----->| /
>>> +----------+ ,
>>>
>>> After discussions w/ Stephen Boyd the clock tree associated with this
>>> hardware block was exported in Linux as:
>>>
>>> vbattb-xtal
>>> xbyp
>>> xc
>>> mux
>>> vbattbclk
>>>
>>> where:
>>> - input-xtal is the input clock (connected to RTXIN, RTXOUT pins)
>>> - xc, xbyp are mux inputs
>>> - mux is the internal mux
>>> - vbattclk is the gate clock that feeds in the end the RTC
>>>
>>> to allow selecting the input of the MUX though assigned-clock DT
>>> properties, using the already existing clock drivers and avoid adding
>>> other DT properties. If the crystal is connected on RTXIN,
>>> RTXOUT pins the XC will be selected as mux input. If an external clock
>>> device is connected on RTXIN, RTXOUT pins the XBYP will be selected as
>>> mux input.
>>>
>>> The load capacitance of the internal crystal can be configured
>>> with renesas,vbattb-load-nanofarads DT property.
>>>
>>> Reviewed-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
>>> Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@xxxxxxxxxxxxxx>
>
>>> --- a/drivers/clk/renesas/Kconfig
>>> +++ b/drivers/clk/renesas/Kconfig
>>> @@ -237,6 +237,10 @@ config CLK_RZV2H
>>> bool "RZ/V2H(P) family clock support" if COMPILE_TEST
>>> select RESET_CONTROLLER
>>>
>>> +config CLK_RENESAS_VBATTB
>>> + bool "Renesas VBATTB clock controller"
>>
>> tristate
>
> Good point.
> However, does it work as a module, or would that break the RTC?
On RZ/G3S the RTC counter needs the clock provided by VBATTB.
I'll try with this as a module.
>
> And this is missing
>
> depends on ARCH_RENESAS || COMPILE_TEST
>
> which I can add while applying.
Thank you!
Claudiu
>
>>
>>> + select RESET_CONTROLLER
>>> +
>
> Gr{oetje,eeting}s,
>
> Geert
>
