linux-kernel - Re: [PATCH v6 2/2] clocksource: Ingenic: Add support for the Ingenic X1000 OST.

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Date:   Fri, 17 Jul 2020 10:02:36 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Zhou Yanjie <zhouyanjie@...yeetech.com>,
        linux-kernel@...r.kernel.org
Cc:     devicetree@...r.kernel.org, robh+dt@...nel.org, tglx@...utronix.de,
        paul@...pouillou.net, dongsheng.qiu@...enic.com,
        aric.pzqi@...enic.com, rick.tyliu@...enic.com,
        yanfei.li@...enic.com, sernia.zhou@...mail.com,
        zhenwenjin@...il.com
Subject: Re: [PATCH v6 2/2] clocksource: Ingenic: Add support for the Ingenic
 X1000 OST.

On 17/07/2020 08:13, Zhou Yanjie wrote:
> Hi Daniel,
> 
> 在 2020/7/17 下午12:20, Daniel Lezcano 写道:
>> On 10/07/2020 19:02, 周琰杰 (Zhou Yanjie) wrote:
>>> X1000 and SoCs after X1000 (such as X1500 and X1830) had a separate
>>> OST, it no longer belongs to TCU. This driver will register both a
>>> clocksource and a sched_clock to the system.
>>>
>>> Tested-by: 周正 (Zhou Zheng) <sernia.zhou@...mail.com>
>>> Co-developed-by: 漆鹏振 (Qi Pengzhen) <aric.pzqi@...enic.com>
>>> Signed-off-by: 漆鹏振 (Qi Pengzhen) <aric.pzqi@...enic.com>
>>> Signed-off-by: 周琰杰 (Zhou Yanjie) <zhouyanjie@...yeetech.com>
>>> Reviewed-by: Paul Cercueil <paul@...pouillou.net>
>>> ---
>>>
>>> Notes:
>>>      v1->v2:
>>>      Fix compile warnings.
>>>      Reported-by: kernel test robot <lkp@...el.com>
>>>           v2->v3:
>>>      No change.
>>>           v3->v4:
>>>      1.Rename "ost" to "sysost"
>>>      1.Remove unrelated changes.
>>>      2.Remove ost_clock_parent enum.
>>>      3.Remove ost->percpu_timer_channel/ost->global_timer_channel.
>>>      4.Set up independent .recalc_rate/.set_rate for percpu/global
>>> timer.
>>>      5.No longer call functions in variable declarations.
>>>           v4->v5:
>>>      Use "of_io_request_and_map()" instead "of_iomap()".
>>>      Suggested-by: Paul Cercueil <paul@...pouillou.net>
>>>           v5->v6:
>>>      No change.
>>>
>>>   drivers/clocksource/Kconfig          |  11 +
>>>   drivers/clocksource/Makefile         |   1 +
>>>   drivers/clocksource/ingenic-sysost.c | 539
>>> +++++++++++++++++++++++++++++++++++
>>>   3 files changed, 551 insertions(+)
>>>   create mode 100644 drivers/clocksource/ingenic-sysost.c
>>>
>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>>> index 91418381fcd4..1bca8b8fb30f 100644
>>> --- a/drivers/clocksource/Kconfig
>>> +++ b/drivers/clocksource/Kconfig
>>> @@ -696,6 +696,17 @@ config INGENIC_TIMER
>>>       help
>>>         Support for the timer/counter unit of the Ingenic JZ SoCs.
>>>   +config INGENIC_SYSOST
>>> +    bool "Clocksource/timer using the SYSOST in Ingenic X SoCs"
>> We usually use silent options and let the platform's Kconfig enable it.
>> We show up the option only when COMPILE_TEST is enabled.
>>
>> Is there a reason to do it differently?
> 
> 
> Do you mean
> 
> bool "Clocksource/timer using the SYSOST in Ingenic X SoCs"
> 
> or
> 
> default MACH_INGENIC ?

Both, no default here.

eg.

bool "Clocksource/timer using the SYSOST in Ingenic X SoCs" if COMPILE_TEST

and

in arch/mips/Kconfig in the config MACH_INGENIC section :

...
select INGENIC_SYSOST
...

> This driver has some origins from "INGENIC_TIMER" driver and
> "INGENIC_OST" driver.
> Early Ingenic processors used TCU (timer/counter unit, has 6 or 8
> generic timer channels) to provide clocksource and clockevent (both with
> only 16bit precision). This part of the processor can only use
> "INGENIC_TIMER" driver.
> 
> Later processors provide an independent 32bit or 64bit timer channel
> (still under TCU, known as ost channel, this channel can not generate
> interrupt) to provid higher precision clocksource. The "INGENIC_OST"
> driver is for this channel. These processors can use "INGENIC_TIMER"
> driver, but using "INGENIC_OST" driver to provide higher precision
> clocksource would be a better choice (clockevent still needs to be
> provided by generic timer channel of TCU, and still 16bit precision).
> 
> And the recent processors provide a SYSOST components, it is independent
> from TCU, including a 64bit timer channel for clocksource and a 32bit
> timer channel for clockevent. Although these processors can also use
> "INGENIC_TIMER" driver, but the better choice is completely independent
> use of "INGENIC_SYSOST" driver to provide higher precision clocksource
> and clockevent.

Ok, the rating should do the job then.

Thanks for the explanation.

> You may have already noticed that this independent SYSOST component is
> like an upgraded and streamlined TCU, which only retains one generic
> timer channel that can generate interrupts, upgrade it from 16bit to
> 32bit, and then retain the 64bit ost channel. so the driver code and
> Kconfig code of this patch is largely referenced
> "INGENIC_TIMER" driver and "INGENIC_OST" driver.
> 
> Thanks and best regards!
> 
>>> +    default MACH_INGENIC
>>> +    depends on MIPS || COMPILE_TEST
>>> +    depends on COMMON_CLK
>>> +    select MFD_SYSCON
>>> +    select TIMER_OF
>>> +    select IRQ_DOMAIN
>>> +    help
>>> +      Support for the SYSOST of the Ingenic X Series SoCs.
>>> +
>> [ ... ]
>>
>>


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