On 31/10/2024 10:26, Claudiu Beznea wrote: > 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. So it will defer, why would this be a problem? This does not look like critical core component, which would halt the system probe (and even then systems like Android put everything as modules). Best regards, Krzysztof
