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

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Date: Wed, 15 May 2024 02:23:47 +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 15/05/2024 02:08, Conor Dooley wrote:
> 
> On Tue, May 14, 2024 at 07:40:02AM +0000, Xingyu Wu wrote:
> > 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.
> 
> There's a push in U-Boot to move devicestrees to use "OF_UPSTREAM", which
> means importing devicetrees directly from Linux and using them in U-Boot. I
> don't really want to merge a patch that would present U-Boot with a problem if
> the VisionFive 2 moved to that model there.
> 
> Cheers,
> Conor.

Would it be better  if I  change the rates of PLL0 and CPU core in the driver not dts,
and avoid the dts of Linux and U-Boot being different?

Thanks,
Xingyu Wu