RE: [PATCH 2/2] arm64: dts: imx8mm: Assign highest opp as suspend opp

[Anson Huang]

Hi, Leonard

> > On 7/4/2019 9:23 AM, Anson.Huang@xxxxxxx wrote:
> > > From: Anson Huang <Anson.Huang@xxxxxxx>
> > >
> > > Assign highest OPP as suspend OPP to reduce suspend/resume latency
> > > on i.MX8MM.
> > >
> > > Signed-off-by: Anson Huang <Anson.Huang@xxxxxxx>
> > > ---
> > >   arch/arm64/boot/dts/freescale/imx8mm.dtsi | 1 +
> > >   1 file changed, 1 insertion(+)
> > >
> > > diff --git a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > > b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > > index b11fc5e..3a62407 100644
> > > --- a/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > > +++ b/arch/arm64/boot/dts/freescale/imx8mm.dtsi
> > > @@ -136,6 +136,7 @@
> > >   			opp-microvolt = <1000000>;
> > >   			opp-supported-hw = <0x8>, <0x3>;
> > >   			clock-latency-ns = <150000>;
> > > +			opp-suspend;
> > >   		};
> > >   	};
> >
> > What if the highest OPP is unavailable due to speed grading? Ideally
> > we should find a way to suspend at the highest *supported* OPP.
> >
> > Maybe the opp-suspend marking could be assigned from imx-cpufreq-dt
> > driver code?
> 
> Yes, this is also my concern, the current OPP driver does NOT handle it well,
> and I was thinking to assigne it from imx-cpufreq-dt driver, 1 option is to
> runtime add "suspend-opp" property into DT OPP node after parsing the
> speed grading fuse and OPP table, but I do NOT like that very much, as we
> need to manually create a property, the other option is to change cpu freq
> policy inside imx-cpufreq-dt driver in suspend/resume callback? Which one
> do you prefer?

After looking through the cpufreq driver, I think we can use below late init function
to assign the suspend_freq, then no need to add "opp-suspend " in DT, and the freq
get from cpufreq_quick_get_max() is already the max supported freq considering the
speed grading and market segment fuse settings, please ignore these 2 patches, I will
send out a imx-cpufreq-dt.c patch with below change to support all SoCs with imx-cpufreq-dt
driver.

+static int __init imx_cpufreq_dt_setup_suspend_opp(void)
+{
+       struct cpufreq_policy *policy = cpufreq_cpu_get(0);
+
+       policy->suspend_freq = cpufreq_quick_get_max(0);
+
+       return 0;
+}
+late_initcall(imx_cpufreq_dt_setup_suspend_opp);

Anson.