Re: [PATCH 0/4] Add smp support for Allwinner A20 and phy arch count timer

[cinifr]

>You seem to be suggesting a kernel change (using CNTPCT), but also
>bootloader changes (setting CNTHCTL.PL1PCTEN) to make this possible at
>all. If the bootloader needs to be modified, why can it not be modified
>to set CNTVOFF (or to boot the kernel in Hyp where it can set it
>itself)?

I think kernel should can support both CNTVCT and CNTPCT. Yes, if
bootloader have set  CNTVOFF to zero, then CNTVCT is OK, kvm guest
using CNTVCT can run more efficient then that using CNTPCT. but if
bootloader dont set it, how about kernel booting? I think kernel
should try it's best to boot and run ok even bootload dont set any
generic timer register including  CNTVOFF  and  CNTHCTL. So i gave a
compile options using  CNTPCT. That is only options, If CNTVCT can not
working, you have others choice.
Of cause, It is best that kerne can select which timer count is used
in running time,

>I'm not sure what you mean by selecting which timer to use be reading
>the current running mode. We currently decide to use CNTVCT if booted in
>PL1, or CNTPCT if booted in Hyp. I assume this isn't the mode you're
>referring to?
Yep, kernel can run PL1 NS=1, PL1 NS=0, PL2. If kernel can know
current running Mode.then kernel can chose which timer is OK in
running time. 1: If kernel is runing at PL2 and PL1 NS=0, then CNTPCT
is OK in any case even CNTVOFF is not zero and CNTHCTL.PL1PCTEN is
zero. 2: if kernel is running at  PL1 NS=1,then kernel maybe should
select CNTVCT. But it has risk to using CNTVCT when CNTVOFF is not
zero.
How to deal with the case CNTHCTL.PL1PCTEN is zero and  CNTVOFF is not
zero? current kernel cant using any arch timer incluing   CNTVCT and
CNTPCT. with this case, I think kernel should use CNTVCT by other
ways: Kernel runing CPUn read CNTVCT and save it to  local variable
for example InitVctVALUEn in initialization, then kernel running CPUn
read timer later return a value as  ReadTIMERn=CNTVCTn-InitVctVALUEn,
This way can run in any  generic timer registe set and in any kernel
runing mode. I try to write this patch for new way. But the new way
should need more time than old in read timer funcation  because it
need more calculate.

.
Thanks for your question.

On 12 September 2013 22:39, Mark Rutland <mark.rutland@xxxxxxx> wrote:
> On Thu, Sep 12, 2013 at 07:51:23AM +0100, Fan Rong wrote:
>> The patchs add smp support for Allwinner A20. It add cpuregister node
>> in dts forsmp configure. The patchs also add a options for phy count
>> timer to replace vir count timer as ARM arch timer clocksource. About
>> ARM arch timer: 1. Current kernel use vir count timer, vir count timer
>> can be accessed in any cpu mode for kernel, but it need bootloader set
>> vir count offset rigister zero at first. 2. Phy count timer can be
>> accessed in most cpu mode for kernel except NS-PL1 mode when register
>> CNTHCTL.PL1PCTEN is set to zero. To ensure to use phy count timer,
>> bootloader should set register CNTHCTL.PL1PCTEN is 1 at first. At all,
>> to ensure kernel can use arch timer, bootload should set some generic
>> timer register(cntvoff or cnthctl) at first. the kernel should select
>> which count timer by reading current kernel running mode.
>
> Sorry, but I find the above text difficult to understand. It jumps
> between several issues and isn't well formatted.
>
> You seem to be suggesting a kernel change (using CNTPCT), but also
> bootloader changes (setting CNTHCTL.PL1PCTEN) to make this possible at
> all. If the bootloader needs to be modified, why can it not be modified
> to set CNTVOFF (or to boot the kernel in Hyp where it can set it
> itself)?
>
> I'm not sure what you mean by selecting which timer to use be reading
> the current running mode. We currently decide to use CNTVCT if booted in
> PL1, or CNTPCT if booted in Hyp. I assume this isn't the mode you're
> referring to?
>
> Thanks,
> Mark.
>
>>
>> Fan Rong (4):
>>   Add smp support for Allwinner A20(sunxi 7i).
>>   Add cpuconfig nodes in dts for smp configure.
>>   Add physical count arch timer support for clocksource in ARMv7.
>>   Add arch count timer node in dts for Allwinner A20(sunxi 7i).
>>
>>  arch/arm/boot/dts/sun7i-a20.dtsi     |   18 +-
>>  arch/arm/include/asm/arch_timer.h    |   11 ++
>>  arch/arm/mach-sunxi/Makefile         |    2 +
>>  arch/arm/mach-sunxi/headsmp.S        |   12 ++
>>  arch/arm/mach-sunxi/platform.h       |  346 ++++++++++++++++++++++++++++++++++
>>  arch/arm/mach-sunxi/platsmp.c        |  166 ++++++++++++++++
>>  arch/arm/mach-sunxi/sunxi.c          |    4 +
>>  drivers/clocksource/Kconfig          |    8 +
>>  drivers/clocksource/arm_arch_timer.c |   10 +-
>>  9 files changed, 574 insertions(+), 3 deletions(-)
>>  create mode 100644 arch/arm/mach-sunxi/headsmp.S
>>  create mode 100644 arch/arm/mach-sunxi/platform.h
>>  create mode 100644 arch/arm/mach-sunxi/platsmp.c
>>
>> --
>> 1.7.9.5
>>
>>
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