Re: [PATCH v6] clk: starfive: jh7110-sys: Fix lower rate of CPUfreq by setting PLL0 rate to 1.5GHz

[Conor Dooley <conor@kernel.org>]

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On Thu, Aug 08, 2024 at 03:44:49AM +0000, Xingyu Wu wrote:
> On 06/08/2024 17:58, Emil Renner Berthing wrote:
> > 
> > Xingyu Wu wrote:
> > > CPUfreq supports 4 cpu frequency loads on 375/500/750/1500MHz. But now
> > > PLL0 rate is 1GHz and the cpu frequency loads become
> > > 250/333/500/1000MHz in fact. The PLL0 rate should be default set to
> > > 1.5GHz and set the divider of cpu_core clock to 2 in safe.
> > >
> > > To keeo the cpu frequency stable when setting PLL0, the parent clock
> > > of the cpu_root clock needs to be switched from PLL0 to another parent
> > > clock and add notifier function to do this for PLL0 clock. In the
> > > function, the cpu_root clock should be operated by saving its current
> > > parent and setting a new safe parent (osc clock) before setting the
> > > PLL0 clock rate. After setting PLL0 rate, it should be switched back
> > > to the original parent clock.
> > >
> > > To keep the DTS same in Linux and U-Boot and the PLL0 rate is 1GHz in
> > > U-Boot, the PLL0 rate should be set to 1.5GHz in the driver instead of
> > > DTS.
> > >
> > > Fixes: e2c510d6d630 ("riscv: dts: starfive: Add cpu scaling for JH7110
> > > SoC")
> > > Signed-off-by: Xingyu Wu <xingyu.wu@starfivetech.com>
> > > ---
> > >
> > > Hi Stephen and Emil,
> > >
> > > This patch is to fix the lower rate of CPUfreq by adding the notifier
> > > for PLL0 clock and changing the PLL0 rate to 1.5GHz.
> > >
> > > To keep the DTS same in Linux and U-Boot as Conor wants[1] and the
> > > PLL0 rate is 1GHz in U-Boot, the PLL0 rate should be set to 1.5GHz in
> > > the driver instead of DTS.
> > >
> > > [1]:
> > > https://lore.kernel.org/all/20240515-reorder-even-8b9eebd91b45@spud/
> > >
> > > Thanks,
> > > Xingyu Wu
> > >
> > > ---
> > >  .../clk/starfive/clk-starfive-jh7110-sys.c    | 54 ++++++++++++++++++-
> > >  drivers/clk/starfive/clk-starfive-jh71x0.h    |  2 +
> > >  2 files changed, 54 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/drivers/clk/starfive/clk-starfive-jh7110-sys.c
> > > b/drivers/clk/starfive/clk-starfive-jh7110-sys.c
> > > index 8f5e5abfa178..7469981fb405 100644
> > > --- a/drivers/clk/starfive/clk-starfive-jh7110-sys.c
> > > +++ b/drivers/clk/starfive/clk-starfive-jh7110-sys.c
> > > @@ -385,6 +385,32 @@ int jh7110_reset_controller_register(struct
> > > jh71x0_clk_priv *priv,  }
> > > EXPORT_SYMBOL_GPL(jh7110_reset_controller_register);
> > >
> > > +/*
> > > + * This clock notifier is called when the rate of PLL0 clock is to be changed.
> > > + * The cpu_root clock should save the curent parent clock and swicth
> > > +its parent
> > > + * clock to osc before PLL0 rate will be changed. Then swicth its
> > > +parent clock
> > > + * back after the PLL0 rate is completed.
> > > + */
> > > +static int jh7110_pll0_clk_notifier_cb(struct notifier_block *nb,
> > > +				       unsigned long action, void *data) {
> > > +	struct jh71x0_clk_priv *priv = container_of(nb, struct jh71x0_clk_priv,
> > pll_clk_nb);
> > > +	struct clk *cpu_root = priv->reg[JH7110_SYSCLK_CPU_ROOT].hw.clk;
> > > +	int ret = 0;
> > > +
> > > +	if (action == PRE_RATE_CHANGE) {
> > > +		struct clk *osc = clk_get(priv->dev, "osc");
> > > +
> > > +		priv->original_clk = clk_get_parent(cpu_root);
> > > +		ret = clk_set_parent(cpu_root, osc);
> > > +		clk_put(osc);
> > > +	} else if (action == POST_RATE_CHANGE) {
> > > +		ret = clk_set_parent(cpu_root, priv->original_clk);
> > > +	}
> > > +
> > > +	return notifier_from_errno(ret);
> > > +}
> > > +
> > >  static int __init jh7110_syscrg_probe(struct platform_device *pdev)
> > > {
> > >  	struct jh71x0_clk_priv *priv;
> > > @@ -413,7 +439,11 @@ static int __init jh7110_syscrg_probe(struct
> > platform_device *pdev)
> > >  		if (IS_ERR(priv->pll[0]))
> > >  			return PTR_ERR(priv->pll[0]);
> > >  	} else {
> > > -		clk_put(pllclk);
> > > +		priv->pll_clk_nb.notifier_call = jh7110_pll0_clk_notifier_cb;
> > > +		ret = clk_notifier_register(pllclk, &priv->pll_clk_nb);
> > > +		if (ret)
> > > +			return ret;
> > > +
> > >  		priv->pll[0] = NULL;
> > >  	}
> > >
> > > @@ -501,7 +531,27 @@ static int __init jh7110_syscrg_probe(struct
> > platform_device *pdev)
> > >  	if (ret)
> > >  		return ret;
> > >
> > > -	return jh7110_reset_controller_register(priv, "rst-sys", 0);
> > > +	ret = jh7110_reset_controller_register(priv, "rst-sys", 0);
> > > +	if (ret)
> > > +		return ret;
> > > +
> > > +	/* Set the divider cpu_core to 2 and set the PLL0 rate to 1.5G. */
> > > +	pllclk = clk_get(priv->dev, "pll0_out");
> > > +	if (!IS_ERR(pllclk)) {
> > > +		struct clk *cpu_core = priv-
> > >reg[JH7110_SYSCLK_CPU_CORE].hw.clk;
> > > +
> > > +		ret = clk_set_rate(cpu_core, clk_get_rate(cpu_core) / 2);
> > > +		if (ret)
> > > +			return ret;
> > > +
> > > +		ret = clk_set_rate(pllclk, 1500000000);
> > > +		if (ret)
> > > +			return ret;
> > > +
> > > +		clk_put(pllclk);
> > > +	}
> > > +
> > > +	return 0;
> > 
> > I'm still not a fan of hardcoding cpu frequencies in the driver. You've added the
> > notifiers exactly so that we can use the standard device tree settings for this.
> > 
> > In other words I much prefer v5 of this patchset.
> > 
> > /Emil
> > 
> 
> Thanks, Emil.
> 
> Hi Conor, what do you think about this issue?

Apologies for the delay replying, I didn't realise there was a question
here directed at me. My only real thought on the patchset is that what
is done should not cause problems when the same devicetree is used for
both U-Boot and for the kernel. As long as that's satisfied, I don't
mind how you choose to implement it.

Thanks,
Conor.

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