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From: Vincent Whitchurch <vincent.whitchurch@axis.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-samsung-soc@vger.kernel.org" 
	<linux-samsung-soc@vger.kernel.org>,
	"daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	kernel <kernel@axis.com>,
	"alim.akhtar@samsung.com" <alim.akhtar@samsung.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-arm-kernel@lists.infradead.org" 
	<linux-arm-kernel@lists.infradead.org>, <krzk@kernel.org>
Subject: Re: [PATCH v2 3/4] clocksource/drivers/exynos_mct: Support local-timer-index property
Date: Thu, 7 Apr 2022 09:48:29 +0200	[thread overview]
Message-ID: <20220407074829.GA31389@axis.com> (raw)
In-Reply-To: <20220330082137.GA21079@axis.com>

On Wed, Mar 30, 2022 at 10:21:37AM +0200, Vincent Whitchurch wrote:
> On Mon, Mar 21, 2022 at 09:00:08AM +0100, Marek Szyprowski wrote:
> > Right, I've played a bit with MCT on some older Exynos SoCs (ARM 32bit 
> > based and even Exynos5433) and it looked that none of it enabled MCT FRC 
> > timer in their proprietary firmware. I've even proposed a patch for this 
> > once ([1]), but such approach has been rejected. I think that calling 
> > exynos4_mct_frc_start() unconditionally won't hurt.
> 
> Thank you for looking into this.  The proposal was however not to avoid
> changing when exynos4_mct_frc_start() is called, but to instead skip the
> write to the Timer Enable bit of the G_TCON register if it is already
> set, like in the below patch.  (This is needed to avoid races when the
> FRC is shared between CPUs in an AMP configuration, since TCON can be
> modified for other reasons from the CPU which is using the global
> comparator.)
> 
> If I understand your comment correctly, such a change should not cause
> any difference at least on the platforms you looked at since there
> MCT_G_TCON_START will not have been set at startup.

I needed the frc-shared property anyway to prevent registration of the
clock events so I followed Krzysztof's suggestion of doing this
conditionally and also clearing the resume callback.

WARNING: multiple messages have this Message-ID (diff)
From: Vincent Whitchurch <vincent.whitchurch@axis.com>
To: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: "devicetree@vger.kernel.org" <devicetree@vger.kernel.org>,
	"linux-samsung-soc@vger.kernel.org"
	<linux-samsung-soc@vger.kernel.org>,
	"daniel.lezcano@linaro.org" <daniel.lezcano@linaro.org>,
	"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
	"robh+dt@kernel.org" <robh+dt@kernel.org>,
	kernel <kernel@axis.com>,
	"alim.akhtar@samsung.com" <alim.akhtar@samsung.com>,
	"tglx@linutronix.de" <tglx@linutronix.de>,
	"linux-arm-kernel@lists.infradead.org"
	<linux-arm-kernel@lists.infradead.org>, <krzk@kernel.org>
Subject: Re: [PATCH v2 3/4] clocksource/drivers/exynos_mct: Support local-timer-index property
Date: Thu, 7 Apr 2022 09:48:29 +0200	[thread overview]
Message-ID: <20220407074829.GA31389@axis.com> (raw)
In-Reply-To: <20220330082137.GA21079@axis.com>

On Wed, Mar 30, 2022 at 10:21:37AM +0200, Vincent Whitchurch wrote:
> On Mon, Mar 21, 2022 at 09:00:08AM +0100, Marek Szyprowski wrote:
> > Right, I've played a bit with MCT on some older Exynos SoCs (ARM 32bit 
> > based and even Exynos5433) and it looked that none of it enabled MCT FRC 
> > timer in their proprietary firmware. I've even proposed a patch for this 
> > once ([1]), but such approach has been rejected. I think that calling 
> > exynos4_mct_frc_start() unconditionally won't hurt.
> 
> Thank you for looking into this.  The proposal was however not to avoid
> changing when exynos4_mct_frc_start() is called, but to instead skip the
> write to the Timer Enable bit of the G_TCON register if it is already
> set, like in the below patch.  (This is needed to avoid races when the
> FRC is shared between CPUs in an AMP configuration, since TCON can be
> modified for other reasons from the CPU which is using the global
> comparator.)
> 
> If I understand your comment correctly, such a change should not cause
> any difference at least on the platforms you looked at since there
> MCT_G_TCON_START will not have been set at startup.

I needed the frc-shared property anyway to prevent registration of the
clock events so I followed Krzysztof's suggestion of doing this
conditionally and also clearing the resume callback.

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  reply	other threads:[~2022-04-07  7:48 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-03-08 14:24 [PATCH v2 0/4] clocksource: Add MCT support for ARTPEC-8 Vincent Whitchurch
2022-03-08 14:24 ` Vincent Whitchurch
2022-03-08 14:24 ` [PATCH v2 1/4] dt-bindings: timer: exynos4210-mct: Add ARTPEC-8 MCT Vincent Whitchurch
2022-03-08 14:24   ` Vincent Whitchurch
2022-03-08 14:37   ` Krzysztof Kozlowski
2022-03-08 14:37     ` Krzysztof Kozlowski
2022-03-08 14:24 ` [PATCH v2 2/4] dt-bindings: timer: exynos4210-mct: Support using only local timer Vincent Whitchurch
2022-03-08 14:24   ` Vincent Whitchurch
2022-03-08 14:44   ` Krzysztof Kozlowski
2022-03-08 14:44     ` Krzysztof Kozlowski
2022-03-08 14:24 ` [PATCH v2 3/4] clocksource/drivers/exynos_mct: Support local-timer-index property Vincent Whitchurch
2022-03-08 14:24   ` Vincent Whitchurch
2022-03-08 14:57   ` Krzysztof Kozlowski
2022-03-08 14:57     ` Krzysztof Kozlowski
2022-03-11 11:35     ` Vincent Whitchurch
2022-03-11 11:35       ` Vincent Whitchurch
2022-03-11 12:51       ` Krzysztof Kozlowski
2022-03-11 12:51         ` Krzysztof Kozlowski
2022-03-21  8:00         ` Marek Szyprowski
2022-03-21  8:00           ` Marek Szyprowski
2022-03-30  8:21           ` Vincent Whitchurch
2022-03-30  8:21             ` Vincent Whitchurch
2022-04-07  7:48             ` Vincent Whitchurch [this message]
2022-04-07  7:48               ` Vincent Whitchurch
2022-03-08 14:24 ` [PATCH v2 4/4] clocksource/drivers/exynos_mct: Enable building on ARTPEC Vincent Whitchurch
2022-03-08 14:24   ` Vincent Whitchurch
2022-03-08 14:58   ` Krzysztof Kozlowski
2022-03-08 14:58     ` Krzysztof Kozlowski

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