From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: Marek Szyprowski <m.szyprowski@samsung.com>,
Will Deacon <will@kernel.org>,
Chanwoo Choi <cw00.choi@samsung.com>
Cc: linux-kernel@vger.kernel.org,
linux-arm-kernel@lists.infradead.org,
Krzysztof Kozlowski <krzk@kernel.org>,
Krzysztof Kozlowski <krzysztof.kozlowski@canonical.com>,
Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 1/2] clocksource/drivers/exynos_mct: Prioritise Arm arch timer on arm64
Date: Mon, 21 Jun 2021 12:24:44 +0200 [thread overview]
Message-ID: <6847bb2f-02ac-35a4-bb7a-491a52325a60@linaro.org> (raw)
In-Reply-To: <95fb8ea3-f409-55ee-6b5c-f19858dd0fab@samsung.com>
On 21/06/2021 12:17, Marek Szyprowski wrote:
[ ... ]
>>>>>> I'm not sure that exynos mct is working without problem
>>>>>> such as the case of 6282edb72bed.
>>>>>> As described on On ,6282edb72bed the arch timer on exynos SoC
>>>>>> depends on Exynos MCT device. the arch timer is not able to work
>>>>>> without Exynos MCT because of using the common module.
>>>>> Is it possible to change the DT to have a phandle to the exynos_mct, so
>>>>> it will be probed before the arch_arm_timer ?
>>>> I think that DT changes is not proper way to keep the order between
>>>> exynos_mct and arch timer.
>>> exynos4_mct_frc_start() is called unconditionally from probe via
>>> exynos4_clocksource_init() so as long as the mct probes first, then the
>>> arch timer should work, no? The rating shouldn't affect that.
>> How do you ensure the exynos mct is probed before the arch timer ?
>>
>> The Makefile provides the right order, but the dependency is implicit.
>
> In my test systems based on Exynos5433, the bootloader enabled MCT, so
> kernel can also start with arch_timer then switch to MCT. The probe
> order also depend on the order of DT nodes, so with the current dts MCT
> is probed first. This is not the best approach, but so far it works.
Right, generally assuming the firmware is doing the right thing from an
initialization POV is not a good idea :/
But in our case, as pointed by Will, the cpuhotplug ordering gives the
right sequence. So it should be fine.
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next prev parent reply other threads:[~2021-06-21 10:24 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-06-08 15:43 [PATCH 0/2] Use Exynos-MCT timer as wakeup for Arm arch timer Will Deacon
2021-06-08 15:43 ` [PATCH 1/2] clocksource/drivers/exynos_mct: Prioritise Arm arch timer on arm64 Will Deacon
2021-06-09 11:41 ` Krzysztof Kozlowski
2021-06-10 1:03 ` Chanwoo Choi
2021-06-16 15:25 ` Daniel Lezcano
2021-06-17 0:58 ` Chanwoo Choi
2021-06-17 21:47 ` Will Deacon
2021-06-21 9:25 ` Daniel Lezcano
2021-06-21 10:10 ` Will Deacon
2021-06-21 10:18 ` Daniel Lezcano
2021-06-22 2:40 ` Chanwoo Choi
2021-06-22 5:21 ` Daniel Lezcano
2021-06-22 6:42 ` Chanwoo Choi
2021-06-21 10:17 ` Marek Szyprowski
2021-06-21 10:24 ` Daniel Lezcano [this message]
2021-08-26 16:25 ` [tip: timers/core] " tip-bot2 for Will Deacon
2021-06-08 15:43 ` [PATCH 2/2] clocksource/drivers/exynos_mct: Mark MCT device as CLOCK_EVT_FEAT_PERCPU Will Deacon
2021-06-09 11:41 ` Krzysztof Kozlowski
2021-06-17 0:59 ` Chanwoo Choi
2021-08-26 16:25 ` [tip: timers/core] " tip-bot2 for Will Deacon
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