linux-kernel - Re: [PATCH v1 3/3] ARM: tegra: Add DFLL clock support on Tegra 4

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Message-ID: <2480891.iZASKD2KPV@senjougahara>
Date: Mon, 25 Aug 2025 13:20:10 +0900
From: Mikko Perttunen <mperttunen@...dia.com>
To: Svyatoslav Ryhel <clamor95@...il.com>
Cc: Thierry Reding <thierry.reding@...il.com>,
 Jonathan Hunter <jonathanh@...dia.com>,
 Peter De Schrijver <pdeschrijver@...dia.com>,
 Prashant Gaikwad <pgaikwad@...dia.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>,
 "Rafael J. Wysocki" <rafael@...nel.org>,
 Viresh Kumar <viresh.kumar@...aro.org>,
 Philipp Zabel <p.zabel@...gutronix.de>, linux-tegra@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-clk@...r.kernel.org,
 linux-pm@...r.kernel.org
Subject: Re: [PATCH v1 3/3] ARM: tegra: Add DFLL clock support on Tegra 4

On Friday, August 22, 2025 2:19 PM Svyatoslav Ryhel wrote:
> пт, 22 серп. 2025 р. о 06:05 Mikko Perttunen <mperttunen@...dia.com> пише:
> > On Friday, March 21, 2025 6:55 PM Svyatoslav Ryhel wrote:
> > > Add DFLL clock node to common Tegra114 device tree along with clocks
> > > property to cpu node.
> > > 
> > > Signed-off-by: Svyatoslav Ryhel <clamor95@...il.com>
> > > ---
> > > 
> > >  arch/arm/boot/dts/nvidia/tegra114.dtsi | 34 ++++++++++++++++++++++++++
> > >  1 file changed, 34 insertions(+)
> > > 
> > > diff --git a/arch/arm/boot/dts/nvidia/tegra114.dtsi
> > > b/arch/arm/boot/dts/nvidia/tegra114.dtsi index
> > > 341ec0962460..25d063a47ca5
> > > 100644
> > > --- a/arch/arm/boot/dts/nvidia/tegra114.dtsi
> > > +++ b/arch/arm/boot/dts/nvidia/tegra114.dtsi
> > > @@ -4,6 +4,7 @@
> > > 
> > >  #include <dt-bindings/memory/tegra114-mc.h>
> > >  #include <dt-bindings/pinctrl/pinctrl-tegra.h>
> > >  #include <dt-bindings/interrupt-controller/arm-gic.h>
> > > 
> > > +#include <dt-bindings/reset/tegra114-car.h>
> > > 
> > >  #include <dt-bindings/soc/tegra-pmc.h>
> > >  
> > >  #include "tegra114-peripherals-opp.dtsi"
> > > 
> > > @@ -710,6 +711,30 @@ mipi: mipi@...e3000 {
> > > 
> > >               #nvidia,mipi-calibrate-cells = <1>;
> > >       
> > >       };
> > > 
> > > +     dfll: clock@...10000 {
> > > +             compatible = "nvidia,tegra114-dfll";
> > > +             reg = <0x70110000 0x100>, /* DFLL control */
> > > +                   <0x70110000 0x100>, /* I2C output control */
> > > +                   <0x70110100 0x100>, /* Integrated I2C controller */
> > > +                   <0x70110200 0x100>; /* Look-up table RAM */
> > > +             interrupts = <GIC_SPI 62 IRQ_TYPE_LEVEL_HIGH>;
> > > +             clocks = <&tegra_car TEGRA114_CLK_DFLL_SOC>,
> > > +                      <&tegra_car TEGRA114_CLK_DFLL_REF>,
> > > +                      <&tegra_car TEGRA114_CLK_I2C5>;
> > > +             clock-names = "soc", "ref", "i2c";
> > > +             resets = <&tegra_car TEGRA114_RST_DFLL_DVCO>;
> > > +             reset-names = "dvco";
> > > +             #clock-cells = <0>;
> > > +             clock-output-names = "dfllCPU_out";
> > > +             nvidia,sample-rate = <11500>;
> > 
> > Should this be 12500? That would match Tegra124 and a downstream kernel
> > for
> > Tegra114 I have.
> 
> I referred to tegratab and macallan boards in 3.4 kernel which give
> 11500, maybe sample-rate was changed to 12500 later with tegra124
> addition?

That's interesting. I was looking at the public roth (Shield Portable) kernel, 
which does not support Tegra124. I checked the L4T r17 release now, and it 
seems it's a newer version, where the sample rate has been changed to 11500 on 
some boards due to a voltage undershoot issue with vdd_cpu on macallan/
tegratab [1].

So on macallan/tegratab, the vdd_cpu (smps123) ramp rate should be set to 
2.5mV/us and sample-rate to 11500, while on other boards it can be 5mV/us with 
12500 for faster ramping.

[1] https://nv-tegra.nvidia.com/r/plugins/gitiles/linux-2.6/+/
b92cab2d4cb6379aeded80adc4c5d0708c3f038e%5E%21/#F0

Cheers,
Mikko

> 
> > > +             nvidia,droop-ctrl = <0x00000f00>;
> > > +             nvidia,force-mode = <1>;
> > > +             nvidia,cf = <10>;
> > > +             nvidia,ci = <0>;
> > > +             nvidia,cg = <2>;
> > > +             status = "disabled";
> > > +     };
> > > +
> > > 
> > >       mmc@...00000 {
> > >       
> > >               compatible = "nvidia,tegra114-sdhci";
> > >               reg = <0x78000000 0x200>;
> > > 
> > > @@ -841,6 +866,15 @@ cpu@0 {
> > > 
> > >                       device_type = "cpu";
> > >                       compatible = "arm,cortex-a15";
> > >                       reg = <0>;
> > > 
> > > +
> > > +                     clocks = <&tegra_car TEGRA114_CLK_CCLK_G>,
> > > +                              <&tegra_car TEGRA114_CLK_CCLK_LP>,
> > > +                              <&tegra_car TEGRA114_CLK_PLL_X>,
> > > +                              <&tegra_car TEGRA114_CLK_PLL_P>,
> > > +                              <&dfll>;
> > > +                     clock-names = "cpu_g", "cpu_lp", "pll_x", "pll_p",
> > 
> > "dfll";
> > 
> > > +                     /* FIXME: what's the actual transition time? */
> > > +                     clock-latency = <300000>;
> > > 
> > >               };
> > >               
> > >               cpu@1 {