From: Krzysztof Kozlowski <krzk@kernel.org>
To: Arnd Bergmann <arnd@arndb.de>
Cc: Krzysztof Kozlowski <krzk@kernel.org>,
Olof Johansson <olof@lixom.net>,
Kevin Hilman <khilman@kernel.org>,
arm@kernel.org, Krzysztof Kozlowski <k.kozlowski@samsung.com>,
Kukjin Kim <kgene@kernel.org>,
linux-arm-kernel@lists.infradead.org,
linux-samsung-soc@vger.kernel.org, linux-kernel@vger.kernel.org,
Bartlomiej Zolnierkiewicz <b.zolnierkie@samsung.com>,
Javier Martinez Canillas <javier@osg.samsung.com>,
Daniel Lezcano <daniel.lezcano@linaro.org>
Subject: Re: [GIT PULL 1/3] ARM: soc: exynos: Drivers for v4.9
Date: Mon, 19 Sep 2016 17:53:02 +0200 [thread overview]
Message-ID: <20160919155302.GA4447@kozik-book> (raw)
In-Reply-To: <2663426.T8oUku18qe@wuerfel>
On Mon, Sep 19, 2016 at 05:02:40PM +0200, Arnd Bergmann wrote:
> On Sunday, September 18, 2016 6:39:46 PM CEST Krzysztof Kozlowski wrote:
> > Samsung drivers/soc update for v4.9:
> > 1. Allow compile testing of exynos-mct clocksource driver on ARM64.
> > 2. Document Exynos5433 PMU compatible (already used by clkout driver and more
> > will be coming soon).
>
> Pulled into next/drivers, thanks
>
> Just for my understanding: why do we need the exynos-mct driver on ARM64
> but not the delay-timer portion of it?
I think we want all of it but Doug's optimization 3252a646aa2c
("clocksource: exynos_mct: Only use 32-bits where possible") is not
ARM64 friendly. One way of dealing with it would be to prepare two
versions of exynos4_read_current_timer(). One reading only lower 32-bit
value for ARMv7 and second (slow) reading lower and upper for ARMv8.
>
> Is there an advantage in using MCT over the architected timer on these
> chips? If so, should we also have a way to use it as the delay timer?
No, there is no real advantage... except that the SoC has some
interesting "characteristics"... The timers are tightly coupled. Very
tightly. I spent a lot of time and failed to boot my ARMv8 board without
some MCT magic.
Best regards,
Krzysztof
WARNING: multiple messages have this Message-ID (diff)
From: krzk@kernel.org (Krzysztof Kozlowski)
To: linux-arm-kernel@lists.infradead.org
Subject: [GIT PULL 1/3] ARM: soc: exynos: Drivers for v4.9
Date: Mon, 19 Sep 2016 17:53:02 +0200 [thread overview]
Message-ID: <20160919155302.GA4447@kozik-book> (raw)
In-Reply-To: <2663426.T8oUku18qe@wuerfel>
On Mon, Sep 19, 2016 at 05:02:40PM +0200, Arnd Bergmann wrote:
> On Sunday, September 18, 2016 6:39:46 PM CEST Krzysztof Kozlowski wrote:
> > Samsung drivers/soc update for v4.9:
> > 1. Allow compile testing of exynos-mct clocksource driver on ARM64.
> > 2. Document Exynos5433 PMU compatible (already used by clkout driver and more
> > will be coming soon).
>
> Pulled into next/drivers, thanks
>
> Just for my understanding: why do we need the exynos-mct driver on ARM64
> but not the delay-timer portion of it?
I think we want all of it but Doug's optimization 3252a646aa2c
("clocksource: exynos_mct: Only use 32-bits where possible") is not
ARM64 friendly. One way of dealing with it would be to prepare two
versions of exynos4_read_current_timer(). One reading only lower 32-bit
value for ARMv7 and second (slow) reading lower and upper for ARMv8.
>
> Is there an advantage in using MCT over the architected timer on these
> chips? If so, should we also have a way to use it as the delay timer?
No, there is no real advantage... except that the SoC has some
interesting "characteristics"... The timers are tightly coupled. Very
tightly. I spent a lot of time and failed to boot my ARMv8 board without
some MCT magic.
Best regards,
Krzysztof
next prev parent reply other threads:[~2016-09-19 15:53 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-18 16:39 [GIT PULL 0/3] ARM: exynos: Second round of stuff for v4.9 Krzysztof Kozlowski
2016-09-18 16:39 ` Krzysztof Kozlowski
2016-09-18 16:39 ` [GIT PULL 1/3] ARM: soc: exynos: Drivers " Krzysztof Kozlowski
2016-09-18 16:39 ` Krzysztof Kozlowski
2016-09-19 15:02 ` Arnd Bergmann
2016-09-19 15:02 ` Arnd Bergmann
2016-09-19 15:53 ` Krzysztof Kozlowski [this message]
2016-09-19 15:53 ` Krzysztof Kozlowski
2016-10-03 0:25 ` Olof Johansson
2016-10-03 0:25 ` Olof Johansson
2016-10-03 7:48 ` Krzysztof Kozlowski
2016-10-03 7:48 ` Krzysztof Kozlowski
2016-10-03 12:19 ` Kukjin Kim
2016-10-03 12:19 ` Kukjin Kim
2016-10-11 0:46 ` Kukjin Kim
2016-10-11 0:46 ` Kukjin Kim
2016-10-11 0:58 ` Kukjin Kim
2016-10-11 0:58 ` Kukjin Kim
2016-09-18 16:39 ` [GIT PULL 2/3] ARM: dts: exynos: DT for v4.9, second round Krzysztof Kozlowski
2016-09-18 16:39 ` Krzysztof Kozlowski
2016-09-19 15:46 ` Arnd Bergmann
2016-09-19 15:46 ` Arnd Bergmann
2016-09-18 16:39 ` [GIT PULL 3/3] ARM: dts: exynos: pinctrl cleanup for v4.9 Krzysztof Kozlowski
2016-09-18 16:39 ` Krzysztof Kozlowski
2016-09-19 15:48 ` Arnd Bergmann
2016-09-19 15:48 ` Arnd Bergmann
2016-09-19 15:48 ` Arnd Bergmann
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