RE: [PATCH v3] clk: starfive: pll: Fix lower rate of CPUfreq by setting PLL0 rate to 1.5GHz

[Xingyu Wu]

On 2024-04-05 5:28 AM, Samuel Holland wrote:
> 
> Hi Xingyu,
> 
> On 2024-04-03 2:44 AM, Xingyu Wu wrote:
> > On 03/04/2024 15:24, Krzysztof Kozlowski wrote:
> >>
> >> On 03/04/2024 09:19, Xingyu Wu wrote:
> >>> On 03/04/2024 0:18, Krzysztof Kozlowski wrote:
> >>>>
> >>>> On 02/04/2024 11:09, 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
> >>>>> 333/500/500/1000MHz in fact.
> >>>>>
> >>>>> So PLL0 rate should be default set to 1.5GHz. But setting the
> >>>>> PLL0 rate need certain steps:
> >>>>>
> >>>>> 1. Change the parent of cpu_root clock to OSC clock.
> >>>>> 2. Change the divider of cpu_core if PLL0 rate is higher than
> >>>>>    1.25GHz before CPUfreq boot.
> >>>>> 3. Change the parent of cpu_root clock back to PLL0 clock.
> >>>>>
> >>>>> Reviewed-by: Hal Feng <hal.feng@xxxxxxxxxxxxxxxx>
> >>>>> 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 fixes the issue about lower rate of CPUfreq[1] by
> >>>>> setting
> >>>>> PLL0 rate to 1.5GHz.
> >>>>>
> >>>>> In order not to affect the cpu operation, setting the PLL0 rate
> >>>>> need certain steps. 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. Due to
> >>>>> PLL driver boot earlier than SYSCRG driver, cpu_core and cpu_root
> >>>>> clocks are using by ioremap().
> >>>>>
> >>>>> [1]: https://github.com/starfive-tech/VisionFive2/issues/55
> >>>>>
> >>>>> Previous patch link:
> >>>>> v2:
> >>>>> https://lore.kernel.org/all/20230821152915.208366-1-xingyu.wu@star
> >>>>> fi
> >>>>> ve
> >>>>> tech.com/
> >>>>> v1:
> >>>>> https://lore.kernel.org/all/20230811033631.160912-1-xingyu.wu@star
> >>>>> fi
> >>>>> ve
> >>>>> tech.com/
> >>>>>
> >>>>> Thanks,
> >>>>> Xingyu Wu
> >>>>> ---
> >>>>>  .../jh7110-starfive-visionfive-2.dtsi         |   5 +
> >>>>>  .../clk/starfive/clk-starfive-jh7110-pll.c    | 102 ++++++++++++++++++
> >>>>
> >>>> Please do not mix DTS and driver code. That's not really portable.
> >>>> DTS is being exported and used in other projects.
> >>>
> >>> OK, I will submit that in two patches.
> >>>
> >>>>
> >>>> ...
> >>>>
> >>>>>
> >>>>> @@ -458,6 +535,8 @@ static int jh7110_pll_probe(struct
> >>>>> platform_device
> >>>> *pdev)
> >>>>>  	struct jh7110_pll_priv *priv;
> >>>>>  	unsigned int idx;
> >>>>>  	int ret;
> >>>>> +	struct device_node *np;
> >>>>> +	struct resource res;
> >>>>>
> >>>>>  	priv = devm_kzalloc(&pdev->dev, sizeof(*priv), GFP_KERNEL);
> >>>>>  	if (!priv)
> >>>>> @@ -489,6 +568,29 @@ static int jh7110_pll_probe(struct
> >>>>> platform_device
> >>>> *pdev)
> >>>>>  			return ret;
> >>>>>  	}
> >>>>>
> >>>>> +	priv->is_first_set = true;
> >>>>> +	np = of_find_compatible_node(NULL, NULL,
> >>>>> +"starfive,jh7110-syscrg");
> >>>>
> >>>> Your drivers should not do it. It's fragile, hides true link/dependency.
> >>>> Please use phandles.
> >>>>
> >>>>
> >>>>> +	if (!np) {
> >>>>> +		ret = PTR_ERR(np);
> >>>>> +		dev_err(priv->dev, "failed to get syscrg node\n");
> >>>>> +		goto np_put;
> >>>>> +	}
> >>>>> +
> >>>>> +	ret = of_address_to_resource(np, 0, &res);
> >>>>> +	if (ret) {
> >>>>> +		dev_err(priv->dev, "failed to get syscrg resource\n");
> >>>>> +		goto np_put;
> >>>>> +	}
> >>>>> +
> >>>>> +	priv->syscrg_base = ioremap(res.start, resource_size(&res));
> >>>>> +	if (!priv->syscrg_base)
> >>>>> +		ret = -ENOMEM;
> >>>>
> >>>> Why are you mapping other device's IO? How are you going to ensure
> >>>> synced access to registers?
> >>>
> >>> Because setting PLL0 rate need specific steps and use the clocks of SYSCRG.
> >>
> >> That's not a reason to map other device's IO. That could be a reason
> >> for having syscon or some other sort of relationship, like clock or reset.
> >>
> >>> But SYSCRG driver also need PLL clock to be clock source when adding
> >>> clock providers. I tried to add SYSCRG clocks in 'clocks' property
> >>> in DT and use
> >>> clk_get() to get the clocks. But it could not run and crash. So I
> >>> use
> >>> ioremap() instead.
> >>
> >> So instead of properly model the relationship, you entangle the
> >> drivers even more.
> >>
> >> Please come with a proper design for this. I have no clue about your
> >> hardware, but that looks like you are asynchronously configuring the
> >> same hardware in two different places.
> >>
> >> Sorry, that's poor code.
> >>
> >> Best regards,
> >> Krzysztof
> >
> > Hi Krzysztof,
> >
> > If I use the old patch[1] like v2 and set the PLL0 default rate in the
> > SYSCRG driver, will it be better?
> >
> > [1]:
> > https://lore.kernel.org/all/20230821152915.208366-1-xingyu.wu@starfive
> > tech.com/
> 
> Both reparenting cpu_root and enforcing the maximum cpu_core frequency can
> be accomplished with clk notifiers. See for example ccu_mux_notifier_register()
> in drivers/clk/sunxi-ng/ccu_mux.c.
> 

This seems like a good idea. I'll try it.

Thanks,
Xingyu Wu