lkml.org 
[lkml]   [2021]   [Jun]   [25]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 4/4] MIPS: CI20: Add second percpu timer for SMP.
Hi Zhou,

Le ven., juin 25 2021 at 23:19:42 +0800, 周琰杰
<zhouyanjie@wanyeetech.com> a écrit :
> Hi Paul,
>
> 于 Fri, 25 Jun 2021 12:31:17 +0100
> Paul Cercueil <paul@crapouillou.net> 写道:
>
>> Hi Zhou,
>>
>> Le jeu., juin 24 2021 at 23:06:29 +0800, 周琰杰 (Zhou Yanjie)
>> <zhouyanjie@wanyeetech.com> a écrit :
>> > 1.Add a new TCU channel as the percpu timer of core1, this is to
>> > prepare for the subsequent SMP support. The newly added channel
>> > will not adversely affect the current single-core state.
>> > 2.Adjust the position of TCU node to make it consistent with the
>> > order in jz4780.dtsi file.
>>
>> That's a bit superfluous, the order matters when adding new nodes,
>> but once they are added, moving them around only cause annoyance.
>>
>> >
>> > Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@wanyeetech.com>
>> > ---
>> >
>> > Notes:
>> > v2:
>> > New patch.
>> >
>> > v2->v3:
>> > No change.
>> >
>> > arch/mips/boot/dts/ingenic/ci20.dts | 21 +++++++++++----------
>> > 1 file changed, 11 insertions(+), 10 deletions(-)
>> >
>> > diff --git a/arch/mips/boot/dts/ingenic/ci20.dts
>> > b/arch/mips/boot/dts/ingenic/ci20.dts
>> > index 8877c62..70005cc 100644
>> > --- a/arch/mips/boot/dts/ingenic/ci20.dts
>> > +++ b/arch/mips/boot/dts/ingenic/ci20.dts
>> > @@ -118,6 +118,17 @@
>> > assigned-clock-rates = <48000000>;
>> > };
>> >
>> > +&tcu {
>> > + /*
>> > + * 750 kHz for the system timers and 3 MHz for the
>> > clocksources,
>> > + * use channel #0 and #1 for the per cpu system timers,
>> > and use
>> > + * channel #2 for the clocksource.
>> > + */
>> > + assigned-clocks = <&tcu TCU_CLK_TIMER0>, <&tcu
>> > TCU_CLK_TIMER1>,
>> > + <&tcu TCU_CLK_TIMER2>,
>> > <&tcu TCU_CLK_OST>;
>> > + assigned-clock-rates = <750000>, <750000>, <3000000>,
>> > <3000000>;
>>
>> Ideally you'd set TIMER1 to 3 MHz and TIMER2 to 750 kHz, otherwise
>> it
>> kind of breaks support for older kernels (they would still boot, but
>> with a very slow clocksource). So in the new DTS you could use the
>> timer0 clock for CPU #0, timer1 for the clocksource, and timer2+ for
>> cpus > 0.
>
> I checked the ingenic-timer driver, and it seems that the last TCU
> channel is always used as the clocksource in the driver, so it seems
> that we can only use timer2 as the clocksource in smp mode. Maybe we
> should add a note for smp is closed in the comment. And I found that I
> missed a problem, Nikolaus Schaller once reported that because the
> frequency of the tcu timer (only 16bit) used to provide the
> clocksource
> is too high, there will be a chance that the system will get stuck
> before the clocksource is switched to ost. And reducing the
> clocksource
> to 750kz can prevent it from happening. I will add this part to v4.
> When this part is added, both clockevent and clocksource will be
> 750kHz, but the 750kHz clocksource is only temporary, because it will
> then switch to the clocksource provided by ost, and ost works at 3MHz.

Ok, then first change the clocksource to 750 kHz, then update it with
timer2.

Cheers,
-Paul

>
> Thanks and best regards!
>
>>
>> Cheers,
>> -Paul
>>
>> > +};
>> > +
>> > &mmc0 {
>> > status = "okay";
>> >
>> > @@ -522,13 +533,3 @@
>> > bias-disable;
>> > };
>> > };
>> > -
>> > -&tcu {
>> > - /*
>> > - * 750 kHz for the system timer and 3 MHz for the
>> > clocksource,
>> > - * use channel #0 for the system timer, #1 for the
>> > clocksource.
>> > - */
>> > - assigned-clocks = <&tcu TCU_CLK_TIMER0>, <&tcu
>> > TCU_CLK_TIMER1>,
>> > - <&tcu TCU_CLK_OST>;
>> > - assigned-clock-rates = <750000>, <3000000>, <3000000>;
>> > -};
>> > --
>> > 2.7.4
>> >
>>
>


\
 
 \ /
  Last update: 2021-06-25 17:49    [W:0.053 / U:1.060 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site