From mboxrd@z Thu Jan  1 00:00:00 1970
From: slash.tmp@free.fr (Mason)
Date: Wed, 20 May 2015 18:21:45 +0200
Subject: schedule_timeout sleeps too long after dividing CPU frequency
In-Reply-To: <20150518115452.GV2067@n2100.arm.linux.org.uk>
References: <20150514144239.GZ2067@n2100.arm.linux.org.uk>
 <5555BC7E.7010601@free.fr> <20150515095159.GF2067@n2100.arm.linux.org.uk>
 <5555CC1A.5040604@free.fr> <20150515115852.GJ2067@n2100.arm.linux.org.uk>
 <5555EA68.7030006@free.fr> <20150515131521.GK2067@n2100.arm.linux.org.uk>
 <5555FB7F.901@free.fr> <55563C63.8090504@free.fr> <5559CC01.9040306@free.fr>
 <20150518115452.GV2067@n2100.arm.linux.org.uk>
Message-ID: <555CB499.7060600@free.fr>
To: linux-arm-kernel@lists.infradead.org
List-Id: linux-arm-kernel.lists.infradead.org

Hello Russell,

Thanks for your detailed answer.

On 18/05/2015 13:54, Russell King - ARM Linux wrote:

> For a SoC where WFI is not programmed to cause anything other than
> the architecture specified dormant behaviour, WFI will not cause the
> TWD to stop.

According to the hardware engineers, my SoC does not support any
low-power modes.

But I didn't see the "clean" way to make the kernel aware of this.
Is this an acceptable patch? (I have my doubts.)


diff --git a/arch/arm/kernel/smp_twd.c b/arch/arm/kernel/smp_twd.c
index 6591e26..300f13a 100644
--- a/arch/arm/kernel/smp_twd.c
+++ b/arch/arm/kernel/smp_twd.c
@@ -295,6 +295,10 @@ static void twd_timer_setup(void)
        clk->name = "local_timer";
        clk->features = CLOCK_EVT_FEAT_PERIODIC | CLOCK_EVT_FEAT_ONESHOT |
                        CLOCK_EVT_FEAT_C3STOP;
+#ifdef CONFIG_TANGOX
+       /*** Tango does not implement low power modes ***/
+       clk->features &= ~CLOCK_EVT_FEAT_C3STOP;
+#endif
        clk->rating = 350;
        clk->set_mode = twd_set_mode;
        clk->set_next_event = twd_set_next_event;


Regards.