linux-kernel - Re: [PATCH v7 2/3] clocksource: Add JH7110 timer driver

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Message-ID: <540136d4-6f8f-49a6-80ff-cc621f2f462b@starfivetech.com>
Date:   Fri, 27 Oct 2023 17:17:30 +0800
From:   Xingyu Wu <xingyu.wu@...rfivetech.com>
To:     Daniel Lezcano <daniel.lezcano@...aro.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Emil Renner Berthing <emil.renner.berthing@...onical.com>,
        Christophe JAILLET <christophe.jaillet@...adoo.fr>
CC:     <linux-riscv@...ts.infradead.org>, <devicetree@...r.kernel.org>,
        "Rob Herring" <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Albert Ou <aou@...s.berkeley.edu>,
        Philipp Zabel <p.zabel@...gutronix.de>,
        Walker Chen <walker.chen@...rfivetech.com>,
        Samin Guo <samin.guo@...rfivetech.com>,
        <linux-kernel@...r.kernel.org>, Conor Dooley <conor@...nel.org>
Subject: Re: [PATCH v7 2/3] clocksource: Add JH7110 timer driver

On 2023/10/25 22:39, Daniel Lezcano wrote:
> 
> Hi Xingyu,
> 
> 
> On 25/10/2023 11:04, Xingyu Wu wrote:
>> On 2023/10/24 22:56, Daniel Lezcano wrote:
>>>
>>> Hi Xingyu,
>>>
>>>
>>> On 19/10/2023 07:35, Xingyu Wu wrote:
>>>> Add timer driver for the StarFive JH7110 SoC.
>>>
>>> As it is a new timer, please add a proper nice description explaining the timer hardware, thanks.
>>
>> OK. Will add the description in next version.
>>
>>>
>>>> Signed-off-by: Xingyu Wu <xingyu.wu@...rfivetech.com>
>>>> ---
>>>>    MAINTAINERS                        |   7 +
>>>>    drivers/clocksource/Kconfig        |  11 +
>>>>    drivers/clocksource/Makefile       |   1 +
>>>>    drivers/clocksource/timer-jh7110.c | 380 +++++++++++++++++++++++++++++
>>>>    4 files changed, 399 insertions(+)
>>>>    create mode 100644 drivers/clocksource/timer-jh7110.c
>>>>
>>>> diff --git a/MAINTAINERS b/MAINTAINERS
>>>> index 7a7bd8bd80e9..91c09b399131 100644
>>>> --- a/MAINTAINERS
>>>> +++ b/MAINTAINERS
>>>> @@ -20473,6 +20473,13 @@ S:    Maintained
>>>>    F:    Documentation/devicetree/bindings/sound/starfive,jh7110-tdm.yaml
>>>>    F:    sound/soc/starfive/jh7110_tdm.c
>>>>    +STARFIVE JH7110 TIMER DRIVER
>>>> +M:    Samin Guo <samin.guo@...rfivetech.com>
>>>> +M:    Xingyu Wu <xingyu.wu@...rfivetech.com>
>>>> +S:    Supported
>>>> +F:    Documentation/devicetree/bindings/timer/starfive,jh7110-timer.yaml
>>>> +F:    drivers/clocksource/timer-jh7110.c
>>>> +
>>>>    STARFIVE JH71X0 CLOCK DRIVERS
>>>>    M:    Emil Renner Berthing <kernel@...il.dk>
>>>>    M:    Hal Feng <hal.feng@...rfivetech.com>
>>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>>>> index 0ba0dc4ecf06..821abcc1e517 100644
>>>> --- a/drivers/clocksource/Kconfig
>>>> +++ b/drivers/clocksource/Kconfig
>>>> @@ -641,6 +641,17 @@ config RISCV_TIMER
>>>>          is accessed via both the SBI and the rdcycle instruction.  This is
>>>>          required for all RISC-V systems.
>>>>    +config STARFIVE_JH7110_TIMER
>>>> +    bool "Timer for the STARFIVE JH7110 SoC"
>>>> +    depends on ARCH_STARFIVE || COMPILE_TEST
>>>
>>> You may want to use ARCH_STARFIVE only if the platform can make this timer optional. Otherwise, set the option from the platform Kconfig and put the bool "bla bla" if COMPILE_TEST
>>
>> Yes, this timer only be used on the StarFive SoC. So I intend to modify to this:
>>
>> bool "Timer for the STARFIVE JH7110 SoC" if COMPILE_TEST
>> depends on ARCH_STARFIVE
> 
> In this case, you should change the platform config and select the timer from there. Remove the depends on ARCH_STARFIVE so it is possible enable cross test compilation. Otherwise COMPILE_TEST will not work on other platforms.
> 
> [ ... ]
> 

It is not a kernel timer or clocksource. It will not work on other platforms and is just used on the JH7110 SoC.
I think I needn't remove it. Maybe I modify to this:

bool "Timer for the STARFIVE JH7110 SoC" if COMPILE_TEST
depends on ARCH_STARFIVE || COMPILE_TEST

>>>> +struct jh7110_clkevt {
>>>> +    struct clock_event_device evt;
>>>> +    struct clocksource cs;
>>>> +    bool cs_is_valid;
>>>> +    struct clk *clk;
>>>> +    struct reset_control *rst;
>>>> +    u32 rate;
>>>> +    u32 reload_val;
>>>> +    void __iomem *base;
>>>> +    char name[sizeof("jh7110-timer.chX")];
>>>> +};
>>>> +
>>>> +struct jh7110_timer_priv {
>>>> +    struct clk *pclk;
>>>> +    struct reset_control *prst;
>>>> +    struct jh7110_clkevt clkevt[JH7110_TIMER_CH_MAX];
>>>
>>> Why do you need several clock events and clock sources ?
>>
>> This timer has four counters (channels) which run independently. So each counter can have its own clock event and clock source to configure different settings.
> 
> The kernel only needs one clocksource. Usually multiple clockevents are per-cpu based system.
> 
> The driver does not seem to have a per cpu timer but just initializing multiple clockevents which will end up unused, wasting energy.
> 
> 

The board of the StarFive JH7110 SoC has two types of timer : riscv-timer and jh7110-timer. It boots by riscv-timer(clocksource) and the jh7110-timer is optional and additional.
I think I should initialize the four channels of jh7110-timer as clockevents not clocksource pre-cpu.

Thanks,
Xingyu Wu