linux-kernel - RE: [PATCH v5 0/2] Add notifier for PLL0 clock and set it 1.5GHz on

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Message-ID:
 <NTZPR01MB0956A7393097129D3CD048EB9FE32@NTZPR01MB0956.CHNPR01.prod.partner.outlook.cn>
Date: Tue, 14 May 2024 07:40:02 +0000
From: Xingyu Wu <xingyu.wu@...rfivetech.com>
To: Conor Dooley <conor@...nel.org>
CC: Michael Turquette <mturquette@...libre.com>, Stephen Boyd
	<sboyd@...nel.org>, Emil Renner Berthing
	<emil.renner.berthing@...onical.com>, Rob Herring <robh@...nel.org>,
	Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>, Paul Walmsley
	<paul.walmsley@...ive.com>, Palmer Dabbelt <palmer@...belt.com>, Albert Ou
	<aou@...s.berkeley.edu>, Hal Feng <hal.feng@...rfivetech.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-clk@...r.kernel.org" <linux-clk@...r.kernel.org>,
	"linux-riscv@...ts.infradead.org" <linux-riscv@...ts.infradead.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>
Subject: RE: [PATCH v5 0/2] Add notifier for PLL0 clock and set it 1.5GHz on

On 11/05/2024 20:19, Conor Dooley wrote:
> 
> On Sat, May 11, 2024 at 03:02:56AM +0000, Xingyu Wu wrote:
> > On 11/05/2024 05:05, Conor Dooley wrote:
> > >
> > > On Tue, May 07, 2024 at 02:53:17PM +0800, Xingyu Wu wrote:
> > > > This patch is to add the notifier for PLL0 clock and set the PLL0
> > > > rate to 1.5GHz to fix the lower rate of CPUfreq on the JH7110 SoC.
> > > >
> > > > The first patch is to add the notifier for PLL0 clock. Setting the
> > > > PLL0 rate need the son clock (cpu_root) to switch its parent clock
> > > > to OSC clock and switch it back after setting PLL0 rate. It need
> > > > to use the cpu_root clock from SYSCRG and register the notifier in
> > > > the SYSCRG driver.
> > > >
> > > > The second patch is to set cpu_core rate to 500MHz and PLL0 rate
> > > > to 1.5GHz to fix the problem about the lower rate of CPUfreq on
> > > > the visionfive board. The cpu_core clock rate is set to 500MHz
> > > > first to ensure that the cpu frequency will not suddenly become
> > > > high and the cpu voltage is not enough to cause a crash when the PLL0 is set
> to 1.5GHz.
> > > > The cpu voltage and frequency are then adjusted together by CPUfreq.
> > >
> > > Hmm, how does sequencing work here? If we split the patches between
> > > trees it sounds like without the dts patch, the clock tree would (or
> > > could) crash, or mainline if the clock changes there before the dts
> > > ones do. Am I misunderstanding that?
> >
> > Oh, I think you misunderstood it. Patch 1 (clock driver patch) does
> > not cause the clock tree crash without the patch 2 (dts patch), and it
> > just provides the correct flow of how to change the PLL0 rate. The
> > patch 2 is to set the clock rate of cpu_core and PLL0 rate, which
> > causes the crash without patch 1. Setting cpu_core rate is to avoid crashes by
> insufficient cpu voltage when setting PLL0 rate.
> 
> So is the problem in the other direction then? My dts tree will crash if I apply the
> dts change without the clock patch?

Sorry, I tested it and it could not crash using only dts patch. It can separate the
patches and use it individually.

> Additionally, what about U-Boot? Will it have problems if the dts is imported
> there without changes to its clock driver?
> 

It is not apply to U-Boot. In the U-Boot, the PLL0 rate should be 1GHz to for GMAC
and PMIC to work. But now the PLL0 rate should be 1.5GHz in the Linux.

Best regards,
Xingyu Wu