From: khilman@linaro•org (Kevin Hilman)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v2 17/18] ARM: OMAP4+: CPUidle: Add OMAP5 idle driver support
Date: Wed, 03 Apr 2013 14:25:05 -0700 [thread overview]
Message-ID: <87fvz7qpce.fsf@linaro.org> (raw)
In-Reply-To: <1364205910-32392-18-git-send-email-santosh.shilimkar@ti.com> (Santosh Shilimkar's message of "Mon, 25 Mar 2013 15:35:09 +0530")
Santosh Shilimkar <santosh.shilimkar@ti•com> writes:
> The OMAP5 idle driver can re-use OMAP4 CPUidle driver implementation thanks
> to compatible MPUSS design.
>
> Though unlike OMAP4, on OMAP5 devices, MPUSS CSWR (Close Switch
> Retention) power states can be achieved with respective power states
> on CPU0 and CPU1 power domain. This mode was broken on OMAP4 devices
> because of hardware limitation.
I'm a bit confused by the description here.
I gather from the code that this means that CPU0 and CPU1 can hit CSWR
independently, correct?
> Also there is no CPU low power entry order requirement like
> master CPU etc for CSWR C-state, which is icing on the cake.
Even on secure devices?
> Code makes use of voting scheme for cluster low power state to support
> MPUSS CSWR C-state.
The voting scheme and associated locking should be better described
here, or commented in the code itself.
> Supported OMAP5 CPUidle C-states:
> C1 - CPU0 ON(WFI) + CPU1 ON(WFI) + MPUSS ON
> C2 - CPU0 CSWR + CPU1 CSWR + MPUSS CSWR
> C3 - CPU0 OFF + CPU1 OFF + MPUSS OSWR
>
> Acked-by: Nishanth Menon <nm@ti•com>
> Signed-off-by: Santosh Shilimkar <santosh.shilimkar@ti•com>
[...]
> +static int omap_enter_idle_smp(struct cpuidle_device *dev,
> + struct cpuidle_driver *drv,
> + int index)
> +{
> + struct idle_statedata *cx = state_ptr + index;
> + int cpu_id = smp_processor_id();
> + unsigned long flag;
> +
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_ENTER, &cpu_id);
I think the CPUidle core handles the broadcast notification now.
> + raw_spin_lock_irqsave(&mpu_lock, flag);
> + cx->mpu_state_vote++;
How about using an atomic_t and atomic_inc()/atomic_dec() instead, which
will avoid the need for a spinlock.
Even with that, it still seems potentially racy. Do you need a memory
barrier here to be sure that any changes from another CPU are visible
here, and vice versa?
> + if (cx->mpu_state_vote == num_online_cpus()) {
> + pwrdm_set_logic_retst(mpu_pd, cx->mpu_logic_state);
> + omap_set_pwrdm_state(mpu_pd, cx->mpu_state);
> + }
> + raw_spin_unlock_irqrestore(&mpu_lock, flag);
> +
> + omap4_enter_lowpower(dev->cpu, cx->cpu_state);
> +
> + raw_spin_lock_irqsave(&mpu_lock, flag);
> + if (cx->mpu_state_vote == num_online_cpus())
> + omap_set_pwrdm_state(mpu_pd, PWRDM_POWER_ON);
> + cx->mpu_state_vote--;
> + raw_spin_unlock_irqrestore(&mpu_lock, flag);
> +
> + clockevents_notify(CLOCK_EVT_NOTIFY_BROADCAST_EXIT, &cpu_id);
> +
> + return index;
> +}
Kevin
next prev parent reply other threads:[~2013-04-03 21:25 UTC|newest]
Thread overview: 64+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-03-25 10:04 [PATCH v2 00/18] ARM: OMAP5: PM: Add MPUSS suspend and CPUidle support Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 01/18] ARM: OMAP4+: PM: Consolidate MPU subsystem PM code for re-use Santosh Shilimkar
2013-04-03 19:44 ` Kevin Hilman
2013-04-04 11:32 ` Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 02/18] ARM: OMAP5: PM: Update CPU context register offset Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 03/18] ARM: OMAP4+: PM: Consolidate and use OMAP4 PM code for OMAP5 Santosh Shilimkar
2013-04-03 20:20 ` Kevin Hilman
2013-04-04 11:51 ` Santosh Shilimkar
2013-04-04 11:55 ` Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 04/18] ARM: OMAP5: PM: Set MPUSS-EMIF clock-domain static dependency Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 05/18] ARM: OMAP5: PM: Enables ES2 PM mode by default Santosh Shilimkar
2013-04-03 20:25 ` Kevin Hilman
2013-04-04 12:02 ` Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 06/18] ARM: OMAP5: PM: Enable Mercury retention mode on CPUx powerdomains Santosh Shilimkar
2013-04-03 20:31 ` Kevin Hilman
2013-04-04 12:08 ` Santosh Shilimkar
2013-03-25 10:04 ` [PATCH v2 07/18] ARM: OMAP5: Add init_late() hook to enable pm initialization Santosh Shilimkar
2013-04-03 20:33 ` Kevin Hilman
2013-04-04 12:28 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 08/18] ARM: OMAP5: PM: Add CPU power off in hotplug path Santosh Shilimkar
2013-04-03 20:49 ` Kevin Hilman
2013-04-04 13:23 ` Santosh Shilimkar
2013-04-04 17:31 ` Kevin Hilman
2013-04-05 9:04 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 09/18] ARM: OMAP4+: PM: Restore CPU power state to ON with clockdomain force wakeup method Santosh Shilimkar
2013-04-03 20:54 ` Kevin Hilman
2013-04-04 13:37 ` Santosh Shilimkar
2013-04-04 17:42 ` Kevin Hilman
2013-04-05 9:07 ` Santosh Shilimkar
2013-04-05 11:58 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 10/18] ARM: OMAP5: PM: Add MPU Open Switch Retention support Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 11/18] ARM: OMAP5: PM: Add L2 memory power down support Santosh Shilimkar
2013-04-03 20:58 ` Kevin Hilman
2013-04-04 13:46 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 12/18] ARM: OMAP4: CPUidle: Avoid double idle driver registration Santosh Shilimkar
2013-04-03 21:03 ` Kevin Hilman
2013-04-04 13:47 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 13/18] ARM: OMAP: CPUidle: Unregister drivere on device registration failure Santosh Shilimkar
2013-04-03 21:03 ` Kevin Hilman
2013-04-04 13:48 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 14/18] ARM: OMAP4: CPUidle: Make C-state description field more precise Santosh Shilimkar
2013-04-03 21:05 ` Kevin Hilman
2013-04-04 13:48 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 15/18] ARM: OMAP4+: CPUidle: Consolidate idle driver for OMAP5 support Santosh Shilimkar
2013-04-03 21:10 ` Kevin Hilman
2013-04-04 14:04 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 16/18] ARM: OMAP4+: CPUidle: Deprecate use of omap4_mpuss_read_prev_context_state() Santosh Shilimkar
2013-04-03 21:37 ` Kevin Hilman
2013-04-04 13:59 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 17/18] ARM: OMAP4+: CPUidle: Add OMAP5 idle driver support Santosh Shilimkar
2013-04-03 21:25 ` Kevin Hilman [this message]
2013-04-04 14:16 ` Santosh Shilimkar
2013-04-04 17:55 ` Kevin Hilman
2013-04-05 9:41 ` Santosh Shilimkar
2013-03-25 10:05 ` [PATCH v2 18/18] ARM: OMAP5: PM: handle device instance for warm reset Santosh Shilimkar
2013-03-25 11:46 ` [PATCH v2 00/18] ARM: OMAP5: PM: Add MPUSS suspend and CPUidle support Lokesh Vutla
2013-03-25 12:10 ` Santosh Shilimkar
2013-03-25 12:27 ` Sourav Poddar
2013-03-25 12:47 ` Rajendra Nayak
2013-03-25 13:00 ` Sourav Poddar
2013-04-03 22:52 ` Kevin Hilman
2013-04-04 14:34 ` Santosh Shilimkar
2013-04-04 16:49 ` Santosh Shilimkar
2013-04-04 17:57 ` Kevin Hilman
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