linux-kernel - Re: [PATCH] arm64: Enable SPRD

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Date:   Sun, 11 Feb 2018 19:41:06 +0800
From:   Chunyan Zhang <zhang.lyra@...il.com>
To:     Baolin Wang <baolin.wang@...aro.org>
Cc:     Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        Arnd Bergmann <arnd@...db.de>,
        Linux ARM <linux-arm-kernel@...ts.infradead.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Mark Brown <broonie@...nel.org>,
        Orson Zhai (翟京) 
        <orson.zhai@...eadtrum.com>, nianfu.bai@...eadtrum.com,
        geng.ren@...eadtrum.com
Subject: Re: [PATCH] arm64: Enable SPRD_TIMER

Hi Baolin,

On 7 February 2018 at 11:12, Baolin Wang <baolin.wang@...aro.org> wrote:
> On 7 February 2018 at 10:31, Chunyan Zhang <zhang.lyra@...il.com> wrote:
>> Hi Baolin,
>>
>> On 6 February 2018 at 18:36, Baolin Wang <baolin.wang@...aro.org> wrote:
>>> Enable Spreadtrum timer driver for Spreadtrum plaform, which will be used
>>> as tick broadcast device.
>>>
>>> Signed-off-by: Baolin Wang <baolin.wang@...aro.org>
>>> ---
>>>  arch/arm64/Kconfig.platforms |    1 +
>>>  1 file changed, 1 insertion(+)
>>>
>>> diff --git a/arch/arm64/Kconfig.platforms b/arch/arm64/Kconfig.platforms
>>> index fbedbd8..3e0bbb0 100644
>>> --- a/arch/arm64/Kconfig.platforms
>>> +++ b/arch/arm64/Kconfig.platforms
>>> @@ -224,6 +224,7 @@ config ARCH_TEGRA
>>>
>>>  config ARCH_SPRD
>>>         bool "Spreadtrum SoC platform"
>>> +       select SPRD_TIMER
>>
>> Do we have to select SPRD_TIMER here? SC9836, SC9860 have been working
>> with a minimum system without SPRD TIMER.
>
> Yes, we need register this timer as the tick broadcast device,
> otherwise we will use one hrtimer to be registered the broadcast
> device, which will affect the No-Hz of CPU attaching the
> broadcast-hrtimer.

Again, Spreadtrum's two boards - SC9836/SC9860 - can run into console
without SPRD_TIMER, we can also debug some kernel origianl feature or
some basic drivers on these two boards, such as CoreSight, clock
driver, etc.

In my opinion we should keep the kernel as simple as possible, the
above information can go to the 'help' graph of SPRD_TIMER in its
Kconfig.

Thanks,
Chunyan

>
> --
> Baolin.wang
> Best Regards