From mboxrd@z Thu Jan 1 00:00:00 1970 From: Stephen Warren Subject: Re: [PATCH V2 2/6] ARM: tegra20: cpuidle: add powered-down state for secondary CPU Date: Wed, 05 Dec 2012 15:18:14 -0700 Message-ID: <50BFC826.1020705@wwwdotorg.org> References: <1354701715-24150-1-git-send-email-josephl@nvidia.com> <1354701715-24150-3-git-send-email-josephl@nvidia.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1354701715-24150-3-git-send-email-josephl-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org> Sender: linux-tegra-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Joseph Lo Cc: linux-tegra-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-arm-kernel-IAPFreCvJWM7uuMidbF8XUB+6BGkLq7r@public.gmane.org List-Id: linux-tegra@vger.kernel.org On 12/05/2012 03:01 AM, Joseph Lo wrote: > The powered-down state of Tegra20 requires power gating both CPU cores. > When the secondary CPU requests to enter powered-down state, it saves > its own contexts and then enters WFI. The Tegra20 had a limition to > power down both CPU cores. The secondary CPU must waits for CPU0 in > powered-down state too. If the secondary CPU be woken up before CPU0 > entering powered-down state, then it needs to restore its CPU states > and waits for next chance. > > Be aware of that, you may see the legacy power state "LP2" in the code > which is exactly the same meaning of "CPU power down". > diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c > +static int __cpuinit tegra20_idle_lp2(struct cpuidle_device *dev, > + return (entered_lp2) ? index : 0; No need for the brackets there. BTW, could you Cc Colin Cross on any future revisions of these patches; it'd be good to get his take on them. > diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S > +/* > + * tegra_pen_lock > + * on cpu 0: > + * SCRATCH38 = r2 = flag[0] > + * SCRATCH39 = r3 = flag[1] It would be slightly clearer if that was written: * r2 = flag[0] (in SCRATCH38) * r3 = flag[1] (in SCRATCH39) since the meaning of r2/r3 is what's being selected. > + mov r12, #1 > + str r12, [r2] @ flag[cpu] = 1 > + dsb > + str r12, [r1] @ !turn = cpu Should that be "str r0, [r1]"? Otherwise, you're always writing 1 there, not writing the CPU ID as expected. From mboxrd@z Thu Jan 1 00:00:00 1970 From: swarren@wwwdotorg.org (Stephen Warren) Date: Wed, 05 Dec 2012 15:18:14 -0700 Subject: [PATCH V2 2/6] ARM: tegra20: cpuidle: add powered-down state for secondary CPU In-Reply-To: <1354701715-24150-3-git-send-email-josephl@nvidia.com> References: <1354701715-24150-1-git-send-email-josephl@nvidia.com> <1354701715-24150-3-git-send-email-josephl@nvidia.com> Message-ID: <50BFC826.1020705@wwwdotorg.org> To: linux-arm-kernel@lists.infradead.org List-Id: linux-arm-kernel.lists.infradead.org On 12/05/2012 03:01 AM, Joseph Lo wrote: > The powered-down state of Tegra20 requires power gating both CPU cores. > When the secondary CPU requests to enter powered-down state, it saves > its own contexts and then enters WFI. The Tegra20 had a limition to > power down both CPU cores. The secondary CPU must waits for CPU0 in > powered-down state too. If the secondary CPU be woken up before CPU0 > entering powered-down state, then it needs to restore its CPU states > and waits for next chance. > > Be aware of that, you may see the legacy power state "LP2" in the code > which is exactly the same meaning of "CPU power down". > diff --git a/arch/arm/mach-tegra/cpuidle-tegra20.c b/arch/arm/mach-tegra/cpuidle-tegra20.c > +static int __cpuinit tegra20_idle_lp2(struct cpuidle_device *dev, > + return (entered_lp2) ? index : 0; No need for the brackets there. BTW, could you Cc Colin Cross on any future revisions of these patches; it'd be good to get his take on them. > diff --git a/arch/arm/mach-tegra/sleep-tegra20.S b/arch/arm/mach-tegra/sleep-tegra20.S > +/* > + * tegra_pen_lock > + * on cpu 0: > + * SCRATCH38 = r2 = flag[0] > + * SCRATCH39 = r3 = flag[1] It would be slightly clearer if that was written: * r2 = flag[0] (in SCRATCH38) * r3 = flag[1] (in SCRATCH39) since the meaning of r2/r3 is what's being selected. > + mov r12, #1 > + str r12, [r2] @ flag[cpu] = 1 > + dsb > + str r12, [r1] @ !turn = cpu Should that be "str r0, [r1]"? Otherwise, you're always writing 1 there, not writing the CPU ID as expected.