From: Colin Cross <ccross@android.com>
To: Mark Brown <broonie@opensource.wolfsonmicro.com>
Cc: linux-tegra@vger.kernel.org,
Russell King <linux@arm.linux.org.uk>,
konkers@android.com, linux-kernel@vger.kernel.org,
olof@lixom.net, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v2 20/28] ARM: tegra: cpufreq: Disable cpufreq during suspend
Date: Mon, 24 Jan 2011 10:50:53 -0800 [thread overview]
Message-ID: <AANLkTikrUdLM8VmW5yCndf927E=drZF1gGBwXq6Dj5mW@mail.gmail.com> (raw)
In-Reply-To: <20110124144142.GA16813@sirena.org.uk>
On Mon, Jan 24, 2011 at 6:41 AM, Mark Brown
<broonie@opensource.wolfsonmicro.com> wrote:
> On Sun, Jan 23, 2011 at 06:01:25PM -0800, Colin Cross wrote:
>> Adds a SUSPEND_PREPARE notification hook to drop the frequency to
>> the lowest possible during suspend. This prevents the cpufreq driver
>> from attempting regulator calls after suspend has started - the
>> regulator api can call into drivers that have already been suspended.
>
> Hrm, what's the situation where that happens and why does it cause
> problems? The regulator API doesn't care if suspend is going on, and
> nor do any of the current drivers for regulators. There is an issue
> with keeping things like I2C alive until the bitter end of suspend so
> you've got a control bus to the regulators but that's a generic issue
> which crops up with other subsystems too so a regulator-specific
> workaround seems dodgy.
The end result is that the regulator driver calls the i2c driver after
the i2c driver has been suspended. On Tegra, this happens because of
voltage scaling on the CPU regulator, which can be on the i2c bus. A
sleep in a suspend handler after the i2c bus has been suspended can
cause the cpufreq governor to lower the frequency, and try to lower
the voltage as well.
The problem isn't limited to i2c busses, there are some regulators on
spi busses. You would need to ensure that any driver that has a
regulator consumer suspends before the regulator driver it
communicates with, and that still wouldn't fix cpufreq, which has a
sysdev suspend handler.
> The patch itself seems fine, it's just that it feels like there's
> something else going on.
>
WARNING: multiple messages have this Message-ID (diff)
From: ccross@android.com (Colin Cross)
To: linux-arm-kernel@lists.infradead.org
Subject: [PATCH v2 20/28] ARM: tegra: cpufreq: Disable cpufreq during suspend
Date: Mon, 24 Jan 2011 10:50:53 -0800 [thread overview]
Message-ID: <AANLkTikrUdLM8VmW5yCndf927E=drZF1gGBwXq6Dj5mW@mail.gmail.com> (raw)
In-Reply-To: <20110124144142.GA16813@sirena.org.uk>
On Mon, Jan 24, 2011 at 6:41 AM, Mark Brown
<broonie@opensource.wolfsonmicro.com> wrote:
> On Sun, Jan 23, 2011 at 06:01:25PM -0800, Colin Cross wrote:
>> Adds a SUSPEND_PREPARE notification hook to drop the frequency to
>> the lowest possible during suspend. ?This prevents the cpufreq driver
>> from attempting regulator calls after suspend has started - the
>> regulator api can call into drivers that have already been suspended.
>
> Hrm, what's the situation where that happens and why does it cause
> problems? ?The regulator API doesn't care if suspend is going on, and
> nor do any of the current drivers for regulators. ?There is an issue
> with keeping things like I2C alive until the bitter end of suspend so
> you've got a control bus to the regulators but that's a generic issue
> which crops up with other subsystems too so a regulator-specific
> workaround seems dodgy.
The end result is that the regulator driver calls the i2c driver after
the i2c driver has been suspended. On Tegra, this happens because of
voltage scaling on the CPU regulator, which can be on the i2c bus. A
sleep in a suspend handler after the i2c bus has been suspended can
cause the cpufreq governor to lower the frequency, and try to lower
the voltage as well.
The problem isn't limited to i2c busses, there are some regulators on
spi busses. You would need to ensure that any driver that has a
regulator consumer suspends before the regulator driver it
communicates with, and that still wouldn't fix cpufreq, which has a
sysdev suspend handler.
> The patch itself seems fine, it's just that it feels like there's
> something else going on.
>
next prev parent reply other threads:[~2011-01-24 18:50 UTC|newest]
Thread overview: 140+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-01-24 2:01 [PATCH v2 00/28] Updates for Tegra support in 2.6.39 Colin Cross
2011-01-24 2:01 ` [PATCH v2 01/28] ARM: tegra: irq: Rename gic pointers to avoid conflicts Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-26 7:10 ` Colin Cross
2011-01-26 7:10 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 02/28] ARM: gic: Add functions to save and restore gic state Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-02-01 13:03 ` Russell King - ARM Linux
2011-02-01 13:03 ` Russell King - ARM Linux
2011-01-24 2:01 ` [PATCH v2 03/28] ARM: gic: Export irq chip functions Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 6:39 ` Santosh Shilimkar
2011-01-24 6:39 ` Santosh Shilimkar
2011-01-24 2:01 ` [PATCH v2 04/28] ARM: mm: cache-l2x0: Add support for re-enabling l2x0 Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-25 15:14 ` Catalin Marinas
2011-01-25 15:14 ` Catalin Marinas
2011-01-25 15:41 ` Russell King - ARM Linux
2011-01-25 15:41 ` Russell King - ARM Linux
2011-01-25 18:14 ` Catalin Marinas
2011-01-25 18:14 ` Catalin Marinas
2011-01-25 18:32 ` Santosh Shilimkar
2011-01-25 18:32 ` Santosh Shilimkar
2011-01-25 18:39 ` Will Deacon
[not found] ` <-8932138696981683633@unknownmsgid>
2011-02-04 23:32 ` Colin Cross
2011-02-04 23:32 ` Colin Cross
2011-02-04 23:32 ` Colin Cross
2011-02-04 23:43 ` Russell King - ARM Linux
2011-02-04 23:43 ` Russell King - ARM Linux
[not found] ` <20110204234331.GF8732-l+eeeJia6m9vn6HldHNs0ANdhmdF6hFW@public.gmane.org>
2011-02-05 1:44 ` Colin Cross
2011-02-05 1:44 ` Colin Cross
2011-02-05 1:44 ` Colin Cross
[not found] ` <AANLkTi=fHnivHXHnYrQvdP6JWbEA3t1X3DuBxj5gN3H0-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-05 7:51 ` Santosh Shilimkar
2011-02-05 7:51 ` Santosh Shilimkar
2011-02-05 7:51 ` Santosh Shilimkar
[not found] ` <1bebe4b5c8590059b70a146d5486fa6a-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-05 9:47 ` Russell King - ARM Linux
2011-02-05 9:47 ` Russell King - ARM Linux
2011-02-05 9:47 ` Russell King - ARM Linux
2011-02-05 10:41 ` [PATCH v2 04/28] ARM: mm: cache-l2x0: Add support forre-enabling l2x0 Santosh Shilimkar
2011-02-05 10:41 ` Santosh Shilimkar
2011-02-05 16:36 ` Colin Cross
2011-02-05 16:36 ` Colin Cross
[not found] ` <AANLkTik_r4k_5o+F47vRbGPcWLwfgHgWqhym49XfhBZ9-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2011-02-07 6:13 ` Santosh Shilimkar
2011-02-07 6:13 ` Santosh Shilimkar
2011-02-07 6:13 ` Santosh Shilimkar
2011-01-24 2:01 ` [PATCH v2 05/28] ARM: tegra: Centralize macros to define debug uart base Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 06/28] ARM: tegra: Add api to control internal powergating Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 07/28] ARM: tegra: irqs: Update irq list Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 08/28] ARM: tegra: Add prototypes for subsystem suspend functions Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 09/28] ARM: tegra: clock: Suspend fixes, and add new clocks Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 10/28] ARM: tegra: pinmux: Add missing drive pingroups and fix suspend Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 11/28] ARM: tegra: timer: Add idle and suspend support to timers Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 12/28] ARM: tegra: irq: Add support for suspend wake sources Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 13/28] ARM: tegra: Add suspend and hotplug support Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 7:31 ` Colin Cross
2011-01-24 7:31 ` Colin Cross
2011-01-24 9:07 ` Russell King - ARM Linux
2011-01-24 9:07 ` Russell King - ARM Linux
2011-01-24 9:26 ` Colin Cross
2011-01-24 9:26 ` Colin Cross
2011-01-24 10:15 ` Russell King - ARM Linux
2011-01-24 10:15 ` Russell King - ARM Linux
2011-01-24 2:01 ` [PATCH v2 14/28] ARM: tegra: irq: Add set_wake and set_type support for suspend Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 15/28] ARM: tegra: irq: Add debugfs file to show wake irqs Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-27 19:45 ` Stephen Boyd
2011-01-27 19:45 ` Stephen Boyd
2011-01-24 2:01 ` [PATCH v2 16/28] ARM: tegra: irq: Implement retrigger Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 17/28] ARM: tegra: gpio: Add support for waking from suspend Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 18/28] ARM: tegra: add CPU_IDLE driver Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-27 20:38 ` Stephen Boyd
2011-01-27 20:38 ` Stephen Boyd
2011-01-27 21:51 ` Colin Cross
2011-01-27 21:51 ` Colin Cross
2011-01-27 22:07 ` Colin Cross
2011-01-27 22:07 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 19/28] ARM: tegra: iomap: Add missing devices, fix use of SZ_8, SZ_64 Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 20/28] ARM: tegra: cpufreq: Disable cpufreq during suspend Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 14:41 ` Mark Brown
2011-01-24 14:41 ` Mark Brown
2011-01-24 18:50 ` Colin Cross [this message]
2011-01-24 18:50 ` Colin Cross
2011-01-24 19:35 ` Mark Brown
2011-01-24 19:35 ` Mark Brown
2011-01-24 19:52 ` Colin Cross
2011-01-24 19:52 ` Colin Cross
2011-01-24 20:26 ` Mark Brown
2011-01-24 20:26 ` Mark Brown
2011-01-24 20:52 ` Colin Cross
2011-01-24 20:52 ` Colin Cross
2011-01-24 21:08 ` Mark Brown
2011-01-24 21:08 ` Mark Brown
2011-01-24 21:24 ` Colin Cross
2011-01-24 21:24 ` Colin Cross
2011-01-25 4:26 ` Kyungmin Park
2011-01-25 4:26 ` Kyungmin Park
2011-01-24 2:01 ` [PATCH v2 21/28] ARM: tegra: Allow overriding arch_reset Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 22/28] ARM: tegra: dma: Fix critical data corruption bugs Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 23/28] ARM: tegra: add tegra_defconfig Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 24/28] ARM: tegra: Use writel_relaxed in tegra_init_cache Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 25/28] ARM: tegra: suspend: Save protected aperture across LP0 Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 26/28] ARM: tegra: suspend: protect suspend functions with CONFIG_PM Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 27/28] ARM: tegra: enable emc clock updates after lp0 Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 2:01 ` [PATCH v2 28/28] ARM: tegra: clock: Add forward reference to struct clk Colin Cross
2011-01-24 2:01 ` Colin Cross
2011-01-24 10:26 ` Russell King - ARM Linux
2011-01-24 10:26 ` Russell King - ARM Linux
2011-01-25 1:23 ` Colin Cross
2011-01-25 1:23 ` Colin Cross
2011-01-26 3:19 ` Grant Likely
2011-01-26 3:19 ` Grant Likely
2011-01-26 3:21 ` Colin Cross
2011-01-26 3:21 ` Colin Cross
2011-01-26 4:16 ` Grant Likely
2011-01-26 4:16 ` Grant Likely
2011-01-25 10:56 [PATCH v2 20/28] ARM: tegra: cpufreq: Disable cpufreq during suspend MyungJoo Ham
2011-01-25 12:40 ` Mark Brown
2011-01-25 12:40 ` Mark Brown
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