linux-kernel - Re: [PATCH 3/5] ARC: AXS103: DTS: Add core pll node to manage cpu frequency

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Message-ID: <1503490719.15555.1.camel@synopsys.com>
Date:   Wed, 23 Aug 2017 12:18:40 +0000
From:   Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
To:     Vineet Gupta <Vineet.Gupta1@...opsys.com>,
        "linux-snps-arc@...ts.infradead.org" 
        <linux-snps-arc@...ts.infradead.org>
CC:     "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "mark.rutland@....com" <mark.rutland@....com>,
        Alexey Brodkin <Alexey.Brodkin@...opsys.com>,
        "robh+dt@...nel.org" <robh+dt@...nel.org>,
        "devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: Re: [PATCH 3/5] ARC: AXS103: DTS: Add core pll node to manage cpu
 frequency

On Tue, 2017-08-22 at 13:45 -0700, Vineet Gupta wrote:
> On 08/14/2017 09:12 AM, Eugeniy Paltsev wrote:
> > Add core pll node (core_clk) to manage cpu frequency.
> > core_clk represents pll itself.
> > input_clk represents clock signal source (basically xtal) which
> > comes to pll input.
> > 
> > Signed-off-by: Eugeniy Paltsev <Eugeniy.Paltsev@...opsys.com>
> > ---
> >   arch/arc/boot/dts/axc003.dtsi     | 11 +++++++++--
> >   arch/arc/boot/dts/axc003_idu.dtsi | 11 +++++++++--
> >   2 files changed, 18 insertions(+), 4 deletions(-)
> > 
> > diff --git a/arch/arc/boot/dts/axc003.dtsi
> > b/arch/arc/boot/dts/axc003.dtsi
> > index cc9239e..dca7e39 100644
> > --- a/arch/arc/boot/dts/axc003.dtsi
> > +++ b/arch/arc/boot/dts/axc003.dtsi
> > @@ -24,10 +24,17 @@
> >   
> >   		ranges = <0x00000000 0x0 0xf0000000 0x10000000>;
> >   
> > -		core_clk: core_clk {
> > +		input_clk: input-clk {
> >   			#clock-cells = <0>;
> >   			compatible = "fixed-clock";
> > -			clock-frequency = <90000000>;
> > +			clock-frequency = <33333333>;
> > +		};
> > +
> > +		core_clk: core-clk@80 {
> > +			compatible = "snps,axs10x-arc-pll-clock";
> > +			reg = <0x80 0x10>, <0x100 0x10>;
> > +			#clock-cells = <0>;
> > +			clocks = <&input_clk>;
> >   		};
> >   
> >   		core_intc: archs-intc@cpu {
> > diff --git a/arch/arc/boot/dts/axc003_idu.dtsi
> > b/arch/arc/boot/dts/axc003_idu.dtsi
> > index 4ebb2170..5b56bef 100644
> > --- a/arch/arc/boot/dts/axc003_idu.dtsi
> > +++ b/arch/arc/boot/dts/axc003_idu.dtsi
> > @@ -24,10 +24,17 @@
> >   
> >   		ranges = <0x00000000 0x0 0xf0000000 0x10000000>;
> >   
> > -		core_clk: core_clk {
> > +		input_clk: input-clk {
> >   			#clock-cells = <0>;
> >   			compatible = "fixed-clock";
> > -			clock-frequency = <100000000>;
> > +			clock-frequency = <33333333>;
> > +		};
> > +
> > +		core_clk: core-clk@80 {
> > +			compatible = "snps,axs10x-arc-pll-clock";
> > +			reg = <0x80 0x10>, <0x100 0x10>;
> > +			#clock-cells = <0>;
> > +			clocks = <&input_clk>;
> >   		};
> >   
> >   		core_intc: archs-intc@cpu {
> 
> 
> Do we have a bisectability issue here - isn't system broken
> temporarily at 2/5 - 
> and only 3/5 makes it work again - if so we need to squash them
> together !

Could you please be more specific about this bisectability issue as I
can't see it here.

If we apply 2/5 and don't apply 3/5 we simply won't change frequency
after linux boot. We won't increase frequency so I can't see any
problem here here.



---
The only problem I can see is in 4/5:
I should use
cpu-freq = <90000000>;
instead of
cpu-freq = <100000000>;
in arch/arc/boot/dts/axc003.dtsi
So diff should be like
--------------->8-----------
+       cpus {
+               #address-cells = <1>;
+               #size-cells = <0>;
+
+               cpu@0 {
+                       device_type = "cpu";
+                       compatible = "snps,archs38";
+                       reg = <0>;
+                       cpu-freq = <90000000>;
+                       clocks = <&core_clk>;
+               };
+       };
+
--------------->8-----------

Should I send you v2 respin or you'll fix that up locally?
 
> -Vineet
-- 
 Eugeniy Paltsev