linux-kernel - Re: [PATCH V8 1/2] clocksource: add gx6605s SOC system timer

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Date:   Fri, 21 Sep 2018 01:57:27 +0200
From:   Daniel Lezcano <daniel.lezcano@...aro.org>
To:     Guo Ren <ren_guo@...ky.com>
Cc:     tglx@...utronix.de, robh+dt@...nel.org, mark.rutland@....com,
        arnd@...db.de, linux-kernel@...r.kernel.org,
        devicetree@...r.kernel.org, c-sky_gcc_upstream@...ky.com,
        green.hu@...il.com
Subject: Re: [PATCH V8 1/2] clocksource: add gx6605s SOC system timer

On 21/09/2018 01:31, Guo Ren wrote:
> On Thu, Sep 20, 2018 at 06:06:19PM +0200, Daniel Lezcano wrote:
>> On 20/09/2018 10:03, Guo Ren wrote:
>>> Changelog:
>>>  - Add License and Copyright
>>>  - Use timer-of framework
>>>  - Change name with upstream feedback
>>>  - Use clksource_mmio framework
>>>
>>> Signed-off-by: Guo Ren <ren_guo@...ky.com>
>>> ---
>>>  drivers/clocksource/Kconfig         |   8 ++
>>>  drivers/clocksource/Makefile        |   1 +
>>>  drivers/clocksource/timer-gx6605s.c | 150 ++++++++++++++++++++++++++++++++++++
>>>  3 files changed, 159 insertions(+)
>>>  create mode 100644 drivers/clocksource/timer-gx6605s.c
>>>
>>> diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
>>> index a11f4ba..6d0f18d 100644
>>> --- a/drivers/clocksource/Kconfig
>>> +++ b/drivers/clocksource/Kconfig
>>> @@ -620,4 +620,12 @@ config RISCV_TIMER
>>>  	  is accessed via both the SBI and the rdcycle instruction.  This is
>>>  	  required for all RISC-V systems.
>>>  
>>> +config GX6605S_TIMER
>>> +	bool "Gx6605s SOC system timer driver"
>>> +	depends on CSKY
>>> +	select CLKSRC_MMIO
>>> +	select TIMER_OF
>>> +	help
>>> +	  This option enables support for gx6605s SOC's timer.
>>> +
>>>  endmenu
>>
>> Please make the option not visible as default. There are currently two
>> approaches look at MTK_TIMER and SPRD_TIMER.
> Em ... (ot sure why COMPILE_TEST?):
> 	bool "Gx6605s SOC system timer driver" if COMPILE_TEST
> Hmm?

Because by enabling the COMPILE_TEST, you give the opportunity to
someone without the hardware to cross-compile test your driver and catch
errors very soon before the changes hit your tree.

There are several Continuous Integration loop around running the latest
changes in the kernel (kernelci, 01.org, etc ...) and all drivers with
this flag are compiled tested.

If the option is not set, the timer is silently selected by your
platform's Kconfig only, without giving the opportunity to an non-expert
user to unselect the timer leading to, maybe, an unbootable board.


>>> +static irqreturn_t gx6605s_timer_interrupt(int irq, void *dev)
>>> +{
>>> +	struct clock_event_device *ce = (struct clock_event_device *) dev;
>>
>> nit: no cast is needed.
> Yes, change to:
> 	struct clock_event_device *ce = dev;
> 
> 
>>> +static u64 notrace gx6605s_sched_clock_read(void)
>>> +{
>>> +	void __iomem *base;
>>> +
>>> +	base = timer_of_base(&to) + CLKSRC_OFFSET;
>>> +
>>> +	return (u64) readl_relaxed(base + TIMER_VALUE);
>>
>> nit: extra space after '(u64)'
> Ok
> 	return (u64)readl_relaxed(base + TIMER_VALUE);
> 
> Best Regards
>  Guo Ren
> 


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