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

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Date:   Mon, 14 Aug 2023 11:06:05 +0800
From:   Xingyu Wu <xingyu.wu@...rfivetech.com>
To:     Conor Dooley <conor.dooley@...rochip.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 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.

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