[PATCH v2 2/2] arm64: dts: r8a7796: Add OPPs table for cpu devices

[Geert Uytterhoeven]

Hi Sudeep,

On Tue, Oct 10, 2017 at 4:33 PM, Sudeep Holla <sudeep.holla at arm.com> wrote:
> On 09/10/17 12:57, Geert Uytterhoeven wrote:
>> On Thu, Oct 5, 2017 at 5:04 PM, Sudeep Holla <sudeep.holla at arm.com> wrote:
>>> On 05/10/17 14:26, Simon Horman wrote:
>>>> From: Dien Pham <dien.pham.ry at rvc.renesas.com>
>>>>
>>>> Current, OPP tables are defined temporary,
>>>> they are being evaluated and adjust in future.
>>
>>>> --- a/arch/arm64/boot/dts/renesas/r8a7796.dtsi
>>>> +++ b/arch/arm64/boot/dts/renesas/r8a7796.dtsi
>>>> @@ -46,6 +46,8 @@
>>>>                       power-domains = <&sysc R8A7796_PD_CA57_CPU0>;
>>>>                       next-level-cache = <&L2_CA57>;
>>>>                       enable-method = "psci";
>>>> +                     clocks =<&cpg CPG_CORE R8A7796_CLK_Z>;
>>>> +                     operating-points-v2 = <&cluster0_opp>;
>>>>               };
>>>>
>>>>               a57_1: cpu at 1 {
>>>> @@ -55,6 +57,7 @@
>>>>                       power-domains = <&sysc R8A7796_PD_CA57_CPU1>;
>>>>                       next-level-cache = <&L2_CA57>;
>>>>                       enable-method = "psci";
>>>
>>> Just curious why clocks are not specified in secondaries ?
>>
>> Thanks for noticing, it would indeed be good to describe the clock dependency
>> for all CPU cores.
>>
>>> Does this continue work if I hotplug out CPUs in ascending order and
>>> then hotplug back in descending order ? Also the current driver or OS
>>> may deal with that but not a good assumption when write DT
>>
>> Yes that works, as Linux doesn't handle CPU hotplug details.
>> CPU hotplug is controlled by PSCI, i.e. out of control of the Linux kernel.
>> So it doesn't matter at all what is described here ;-)
>>
>
> Ah no, sorry for not being clear earlier. I was referring to below code
> snippet in drivers/cpufreq/cpufreq-dt.c
>
> 162         cpu_clk = clk_get(cpu_dev, NULL);
>
> 163         if (IS_ERR(cpu_clk)) {
>
> 164                 ret = PTR_ERR(cpu_clk);
>
> 165                 dev_err(cpu_dev, "%s: failed to get clk: %d\n",
> __func__, ret);
> 166                 return ret;
>
> 167         }
>
> Now on systems using r8a7796.dtsi, if you hotplug out all A53s and
> hotplug back in A53_3 first, that should trigger cpufreq_driver->init
> from cpufreq_online which should result in execution above code.
>
> If that takes patch of__of_clk_get_by_name, then that may be problem.
> I was originally point at this when I referred hotplug and was not PSCI
> related.

IC.

That's something we cannot try, as the secure firmware doesn't enable the A53
cores, only the A57 cores.

And disabling all A57 cores is also not possible, as at least one of them
has to be kept running.

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at linux-m68k.org

In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
                                -- Linus Torvalds