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Subject: Re: [PATCH V5 2/7] clocksource: tegra: add Tegra210 timer support
To:     Dmitry Osipenko <digetx@gmail.com>,
        Jon Hunter <jonathanh@nvidia.com>,
        Thierry Reding <thierry.reding@gmail.com>,
        Daniel Lezcano <daniel.lezcano@linaro.org>,
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CC:     <linux-tegra@vger.kernel.org>,
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From:   Joseph Lo <josephl@nvidia.com>
Message-ID: <9437d5b5-5af0-9393-169c-2ebaf384c75c@nvidia.com>
Date:   Fri, 1 Feb 2019 23:37:04 +0800
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On 2/1/19 11:13 PM, Dmitry Osipenko wrote:
> 01.02.2019 17:13, Joseph Lo =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>> On 2/1/19 9:54 PM, Jon Hunter wrote:
>>>
>>> On 01/02/2019 13:11, Dmitry Osipenko wrote:
>>>> 01.02.2019 16:06, Dmitry Osipenko =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>>> 01.02.2019 6:36, Joseph Lo =D0=BF=D0=B8=D1=88=D0=B5=D1=82:
>>>>>> Add support for the Tegra210 timer that runs at oscillator clock
>>>>>> (TMR10-TMR13). We need these timers to work as clock event device an=
d to
>>>>>> replace the ARMv8 architected timer due to it can't survive across t=
he
>>>>>> power cycle of the CPU core or CPUPORESET signal. So it can't be a w=
ake-up
>>>>>> source when CPU suspends in power down state.
>>>>>>
>>>>>> Also convert the original driver to use timer-of API.
>>>>>>
>>>>>> Cc: Daniel Lezcano <daniel.lezcano@linaro.org>
>>>>>> Cc: Thomas Gleixner <tglx@linutronix.de>
>>>>>> Cc: linux-kernel@vger.kernel.org
>>>>>> Signed-off-by: Joseph Lo <josephl@nvidia.com>
>>>>>> Acked-by: Thierry Reding <treding@nvidia.com>
>>>>>> ---
snip.
>>>>>> +}
>>>>>> +TIMER_OF_DECLARE(tegra210_timer, "nvidia,tegra210-timer", tegra210_=
timer_init);
>>>>>> +#else /* CONFIG_ARM */
>>>>>> +static int __init tegra20_init_timer(struct device_node *np)
>>>>>> +{
>>>>> What about T132? Isn't it ARM64 which uses tegra20-timer IP? At least=
 T132 DT suggests so and seems this change will break it.
>>>>>
>>>>> [snip]
>>>>>
>>>>
>>>> Ah, noticed the "depends on ARM" in Kconfig.. Seems okay then.
>>>>
>>>
>>>
>>> This is a good point, because even though we had 'depends on ARM', this
>>> still means that the Tegra132 DT is incorrect.
>>>
>>> Joseph, can you take a quick look at Tegra132?
>>
>> Hi Jon and Dmitry,
>>
>> No worry about T132, T132 uses arch timer (v7). The tegra20 timer driver=
 has never been used. We should fix the dtsi file later.
>=20
> Hi Joseph,
>=20
> So is T132 HW actually incompatible with the tegra20-timer? If it's compa=
tible, then I think the driver's code should be made more universal to supp=
ort T132.
>=20

 From HW point of view, the TIMER1 ~ TIMER4 is compatible with=20
"nvidia,tegra20-timer". But Tegra132 actually has 10 timers which are=20
exactly the same as Tegra30. So it should backward compatible with=20
"nvidia,tegra30-timer", which is tegra_wdt driver now. And Tegra132=20
should never use this driver.

The Tegra timer driver should only be used on Tegra20/30/210, three=20
platforms only. Others use arch timer driver for system timer driver.

So we don't really need to take care the usage on other Tegra platforms.

Thanks,
Joseph