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Date:   Fri, 17 Jul 2020 22:40:09 +0800
From:   Zhou Yanjie <zhouyanjie@...yeetech.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        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.

Hi Daniel,

在 2020/7/17 下午4:02, Daniel Lezcano 写道:
> 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
> ...


Sure, I will do it in the next version.


Thanks and best regards!


>> 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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