linux-kernel - Re: [PATCH v1] clk: starfive: jh7110-sys: Set PLL0 rate to 1.5GHz

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Date:   Mon, 14 Aug 2023 07:57:51 +0100
From:   Conor Dooley <conor.dooley@...rochip.com>
To:     Xingyu Wu <xingyu.wu@...rfivetech.com>
CC:     Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>,
        Emil Renner Berthing <emil.renner.berthing@...onical.com>,
        Conor Dooley <conor@...nel.org>,
        Hal Feng <hal.feng@...rfivetech.com>,
        <linux-kernel@...r.kernel.org>, <linux-clk@...r.kernel.org>
Subject: Re: [PATCH v1] clk: starfive: jh7110-sys: Set PLL0 rate to 1.5GHz

On Mon, Aug 14, 2023 at 11:06:05AM +0800, Xingyu Wu wrote:
> On 2023/8/11 14:43, Conor Dooley wrote:
> > On Fri, Aug 11, 2023 at 11:36:31AM +0800, Xingyu Wu wrote:
> >> Set PLL0 rate to 1.5GHz.
> > 
> > Why are you doing that though?
> 
> Because the CPU frequency scaling is based on 1.5GHz rate on JH7110 SoC.
> And now the PLL clock driver has been accepted and PLL0 is just 1GHz[1].
> [1] https://github.com/starfive-tech/VisionFive2/issues/55
> 
> We should set the PLL0 rate to a correct rate (1.5GHz) and then
> the CPUfreq will work normally.

Please include an explanation in the commit message of the problem this
is addressing.

Also, a Fixes: tag + reported-by?

> Best regards,
> Xingyu Wu
> 
> > 
> > 
> >> Change the parent of cpu_root clock
> >> and the divider of cpu_core before setting.
> >> 
> >> Signed-off-by: Xingyu Wu <xingyu.wu@...rfivetech.com>
> >> ---
> >> 
> >> Hi Stephen and Emil,
> >> 
> >> This patch sets PLL0 rate to 1.5GHz. In order not to affect the cpu 
> >> operation, the cpu_root's parent clock should be changed first.
> >> And the divider of the cpu_core clock should be set to 2 so they
> >> won't crash when setting 1.5GHz without voltage regulation.
> >> 
> >> This patch is based on linux-next which has merge PLL driver on
> >> StarFive JH7110 SoC.
> >> 
> >> Thanks,
> >> Xingyu Wu
> 

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