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

[Xingyu Wu]

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@xxxxxxxxxxxxxxxx>
> > ---
> >
> > 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?

Best regards,
Xingyu Wu