[PATCH v3 0/3] Add imx cpuidle

[PATCH v3 0/3] Add imx cpuidle

[Robert Lee]

Add common imx cpuidle initialization functionality and add a i.MX5 and i.MX6Q
platform cpuidle implementation.

Based on v3.4-rc6 plus recently submitted device tree late_initcall patch:
 http://www.spinics.net/lists/arm-kernel/msg171620.html

v3 changes:
 * removed file introduced in v1 no longer needed after v2 [per Shawn Guo]
 * re-ordered added #includes in alphabetical order [per Shawn Guo]
 * Remove if(!drv) check to allow handling by stack trace [per Sascha Hauer]
 * Added missing return value in error meesage [per Shawn Guo]
 * fixed (void *) casting problem pointed out Sasha Hauer.  Used a different
   type of casting to properly give warning on improper casting:
   	arm_pm_idle = (void (*)(void))imx5_idle;
   Used this casting instead of adding a dummy caller function because
   adding the dummy function appears to unnecessarily introduce the following
   additional operations:
	static void imx5_pm_idle(void)
	{
	  a0:	e1a0c00d 	mov	ip, sp
	  a4:	e92dd800 	push	{fp, ip, lr, pc}
	  a8:	e24cb004 	sub	fp, ip, #4
		imx5_idle();
	  ac:	ebffffd3 	bl	0 <imx5_idle>
	}
	  b0:	e89da800 	ldm	sp, {fp, sp, pc}

v2 changes:
 * Removed some unnecessary  spaces [per Jess Juhl]
 * Added return value for an error message [per Sascha Hauer]
 * Reworked init scheme to use device tree late_initcall [per Sascha and Shawn]
 * Moved imx6q and imx5 cpuidle functionality to existing files.

https://lkml.org/lkml/2012/5/1/363

v1 initial submission:

https://lkml.org/lkml/2012/4/16/644

Robert Lee (3):
  ARM: imx: Add common imx cpuidle init functionality.
  ARM: imx: Add imx5 cpuidle driver
  ARM: imx: Add imx6q cpuidle driver

 arch/arm/mach-imx/mach-imx6q.c           |   19 +++++++
 arch/arm/mach-imx/mm-imx5.c              |   42 ++++++++++++++--
 arch/arm/plat-mxc/Makefile               |    1 +
 arch/arm/plat-mxc/cpuidle.c              |   80 ++++++++++++++++++++++++++++++
 arch/arm/plat-mxc/include/mach/cpuidle.h |   22 ++++++++
 5 files changed, 161 insertions(+), 3 deletions(-)
 create mode 100644 arch/arm/plat-mxc/cpuidle.c
 create mode 100644 arch/arm/plat-mxc/include/mach/cpuidle.h

-- 
1.7.10

[PATCH v3 1/3] ARM: imx: Add common imx cpuidle init functionality.

[Robert Lee]

Add common cpuidle init functionality that can be used by various
imx platforms.

Signed-off-by: Robert Lee <rob.lee@linaro.org>
---
 arch/arm/plat-mxc/Makefile               |    1 +
 arch/arm/plat-mxc/cpuidle.c              |   80 ++++++++++++++++++++++++++++++
 arch/arm/plat-mxc/include/mach/cpuidle.h |   22 ++++++++
 3 files changed, 103 insertions(+)
 create mode 100644 arch/arm/plat-mxc/cpuidle.c
 create mode 100644 arch/arm/plat-mxc/include/mach/cpuidle.h

diff --git a/arch/arm/plat-mxc/Makefile b/arch/arm/plat-mxc/Makefile
index e81290c..63b064b 100644
--- a/arch/arm/plat-mxc/Makefile
+++ b/arch/arm/plat-mxc/Makefile
@@ -16,6 +16,7 @@ obj-$(CONFIG_MXC_ULPI) += ulpi.o
 obj-$(CONFIG_MXC_USE_EPIT) += epit.o
 obj-$(CONFIG_MXC_DEBUG_BOARD) += 3ds_debugboard.o
 obj-$(CONFIG_CPU_FREQ_IMX)    += cpufreq.o
+obj-$(CONFIG_CPU_IDLE) += cpuidle.o
 ifdef CONFIG_SND_IMX_SOC
 obj-y += ssi-fiq.o
 obj-y += ssi-fiq-ksym.o
diff --git a/arch/arm/plat-mxc/cpuidle.c b/arch/arm/plat-mxc/cpuidle.c
new file mode 100644
index 0000000..d4cb511
--- /dev/null
+++ b/arch/arm/plat-mxc/cpuidle.c
@@ -0,0 +1,80 @@
+/*
+ * Copyright 2012 Freescale Semiconductor, Inc.
+ * Copyright 2012 Linaro Ltd.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/cpuidle.h>
+#include <linux/err.h>
+#include <linux/hrtimer.h>
+#include <linux/io.h>
+#include <linux/kernel.h>
+#include <linux/slab.h>
+
+static struct cpuidle_device __percpu * imx_cpuidle_devices;
+
+static void __init imx_cpuidle_devices_uninit(void)
+{
+	int cpu_id;
+	struct cpuidle_device *dev;
+
+	for_each_possible_cpu(cpu_id) {
+		dev = per_cpu_ptr(imx_cpuidle_devices, cpu_id);
+		cpuidle_unregister_device(dev);
+	}
+
+	free_percpu(imx_cpuidle_devices);
+}
+
+int __init imx_cpuidle_init(struct cpuidle_driver *drv)
+{
+	struct cpuidle_device *dev;
+	int cpu_id, ret;
+
+	if (drv->state_count > CPUIDLE_STATE_MAX) {
+		pr_err("%s: state_count exceeds maximum\n", __func__);
+		return -EINVAL;
+	}
+
+	ret = cpuidle_register_driver(drv);
+	if (ret) {
+		pr_err("%s: Failed to register cpuidle driver with error: %d\n",
+			 __func__, ret);
+		return ret;
+	}
+
+	imx_cpuidle_devices = alloc_percpu(struct cpuidle_device);
+	if (imx_cpuidle_devices == NULL) {
+		ret = -ENOMEM;
+		goto unregister_drv;
+	}
+
+	/* initialize state data for each cpuidle_device */
+	for_each_possible_cpu(cpu_id) {
+		dev = per_cpu_ptr(imx_cpuidle_devices, cpu_id);
+		dev->cpu = cpu_id;
+		dev->state_count = drv->state_count;
+
+		ret = cpuidle_register_device(dev);
+		if (ret) {
+			pr_err("%s: Failed to register cpu %u, error: %d\n",
+				__func__, cpu_id, ret);
+			goto uninit;
+		}
+	}
+
+	return 0;
+
+uninit:
+	imx_cpuidle_devices_uninit();
+
+unregister_drv:
+	cpuidle_unregister_driver(drv);
+	return ret;
+}
diff --git a/arch/arm/plat-mxc/include/mach/cpuidle.h b/arch/arm/plat-mxc/include/mach/cpuidle.h
new file mode 100644
index 0000000..bc932d1
--- /dev/null
+++ b/arch/arm/plat-mxc/include/mach/cpuidle.h
@@ -0,0 +1,22 @@
+/*
+ * Copyright 2012 Freescale Semiconductor, Inc.
+ * Copyright 2012 Linaro Ltd.
+ *
+ * The code contained herein is licensed under the GNU General Public
+ * License. You may obtain a copy of the GNU General Public License
+ * Version 2 or later at the following locations:
+ *
+ * http://www.opensource.org/licenses/gpl-license.html
+ * http://www.gnu.org/copyleft/gpl.html
+ */
+
+#include <linux/cpuidle.h>
+
+#ifdef CONFIG_CPU_IDLE
+extern int imx_cpuidle_init(struct cpuidle_driver *drv);
+#else
+static inline int imx_cpuidle_init(struct cpuidle_driver *drv)
+{
+	return -ENODEV;
+}
+#endif
-- 
1.7.10

[PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver

[Robert Lee]

Add imx5 cpuidle driver.

Signed-off-by: Robert Lee <rob.lee@linaro.org>
---
 arch/arm/mach-imx/mm-imx5.c |   42 +++++++++++++++++++++++++++++++++++++++---
 1 file changed, 39 insertions(+), 3 deletions(-)

diff --git a/arch/arm/mach-imx/mm-imx5.c b/arch/arm/mach-imx/mm-imx5.c
index d6b7e9f..0b3a4cc 100644
--- a/arch/arm/mach-imx/mm-imx5.c
+++ b/arch/arm/mach-imx/mm-imx5.c
@@ -20,26 +20,61 @@
 
 #include <mach/hardware.h>
 #include <mach/common.h>
+#include <mach/cpuidle.h>
 #include <mach/devices-common.h>
 #include <mach/iomux-v3.h>
 
 static struct clk *gpc_dvfs_clk;
 
-static void imx5_idle(void)
+static int imx5_idle(void)
 {
+	int ret = 0;
+
 	/* gpc clock is needed for SRPG */
 	if (gpc_dvfs_clk == NULL) {
 		gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
 		if (IS_ERR(gpc_dvfs_clk))
-			return;
+			return -ENODEV;
 	}
 	clk_enable(gpc_dvfs_clk);
 	mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
 	if (!tzic_enable_wake())
 		cpu_do_idle();
+	else
+		ret = -EBUSY;
 	clk_disable(gpc_dvfs_clk);
+
+	return ret;
+}
+
+static int imx5_cpuidle_enter(struct cpuidle_device *dev,
+				struct cpuidle_driver *drv, int idx)
+{
+	int ret;
+
+	ret = imx5_idle();
+
+	if (ret < 0)
+		return ret;
+
+	return idx;
 }
 
+static struct cpuidle_driver imx5_cpuidle_driver = {
+	.name			= "imx5_cpuidle",
+	.owner			= THIS_MODULE,
+	.en_core_tk_irqen	= 1,
+	.states[0]	= {
+		.enter			= imx5_cpuidle_enter,
+		.exit_latency		= 20, /* max latency at 160MHz */
+		.target_residency	= 1,
+		.flags			= CPUIDLE_FLAG_TIME_VALID,
+		.name			= "IMX5 SRPG",
+		.desc			= "CPU state retained,powered off",
+	},
+	.state_count		= 1,
+};
+
 /*
  * Define the MX50 memory map.
  */
@@ -103,7 +138,7 @@ void __init imx51_init_early(void)
 	mxc_set_cpu_type(MXC_CPU_MX51);
 	mxc_iomux_v3_init(MX51_IO_ADDRESS(MX51_IOMUXC_BASE_ADDR));
 	mxc_arch_reset_init(MX51_IO_ADDRESS(MX51_WDOG1_BASE_ADDR));
-	arm_pm_idle = imx5_idle;
+	arm_pm_idle = (void (*)(void))imx5_idle;
 }
 
 void __init imx53_init_early(void)
@@ -238,4 +273,5 @@ void __init imx53_soc_init(void)
 void __init imx51_init_late(void)
 {
 	mx51_neon_fixup();
+	imx_cpuidle_init(&imx5_cpuidle_driver);
 }
-- 
1.7.10

[PATCH v3 3/3] ARM: imx: Add imx6q cpuidle driver

[Robert Lee]

Add basic imx6q cpuidle driver.  For now, only basic WFI state is
supported.  Deeper idle states will be added in the future.

Signed-off-by: Robert Lee <rob.lee@linaro.org>
---
 arch/arm/mach-imx/mach-imx6q.c |   19 +++++++++++++++++++
 1 file changed, 19 insertions(+)

diff --git a/arch/arm/mach-imx/mach-imx6q.c b/arch/arm/mach-imx/mach-imx6q.c
index da6c1d9..4fc1fe7 100644
--- a/arch/arm/mach-imx/mach-imx6q.c
+++ b/arch/arm/mach-imx/mach-imx6q.c
@@ -10,7 +10,9 @@
  * http://www.gnu.org/copyleft/gpl.html
  */
 
+#include <linux/cpuidle.h>
 #include <linux/delay.h>
+#include <linux/export.h>
 #include <linux/init.h>
 #include <linux/io.h>
 #include <linux/irq.h>
@@ -21,6 +23,7 @@
 #include <linux/of_platform.h>
 #include <linux/phy.h>
 #include <linux/micrel_phy.h>
+#include <asm/cpuidle.h>
 #include <asm/smp_twd.h>
 #include <asm/hardware/cache-l2x0.h>
 #include <asm/hardware/gic.h>
@@ -28,8 +31,10 @@
 #include <asm/mach/time.h>
 #include <asm/system_misc.h>
 #include <mach/common.h>
+#include <mach/cpuidle.h>
 #include <mach/hardware.h>
 
+
 void imx6q_restart(char mode, const char *cmd)
 {
 	struct device_node *np;
@@ -86,6 +91,19 @@ static void __init imx6q_init_machine(void)
 	imx6q_pm_init();
 }
 
+static struct cpuidle_driver imx6q_cpuidle_driver = {
+	.name			= "imx6q_cpuidle",
+	.owner			= THIS_MODULE,
+	.en_core_tk_irqen	= 1,
+	.states[0]		= ARM_CPUIDLE_WFI_STATE,
+	.state_count		= 1,
+};
+
+static void __init imx6q_init_late(void)
+{
+	imx_cpuidle_init(&imx6q_cpuidle_driver);
+}
+
 static void __init imx6q_map_io(void)
 {
 	imx_lluart_map_io();
@@ -142,6 +160,7 @@ DT_MACHINE_START(IMX6Q, "Freescale i.MX6 Quad (Device Tree)")
 	.handle_irq	= imx6q_handle_irq,
 	.timer		= &imx6q_timer,
 	.init_machine	= imx6q_init_machine,
+	.init_late      = imx6q_init_late,
 	.dt_compat	= imx6q_dt_compat,
 	.restart	= imx6q_restart,
 MACHINE_END
-- 
1.7.10

Re: [PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver

[Sascha Hauer]

On Mon, May 07, 2012 at 04:16:46PM -0500, Robert Lee wrote:
> Add imx5 cpuidle driver.
> 
> Signed-off-by: Robert Lee <rob.lee@linaro.org>
> ---
>  arch/arm/mach-imx/mm-imx5.c |   42 +++++++++++++++++++++++++++++++++++++++---
>  1 file changed, 39 insertions(+), 3 deletions(-)
> 
> diff --git a/arch/arm/mach-imx/mm-imx5.c b/arch/arm/mach-imx/mm-imx5.c
> index d6b7e9f..0b3a4cc 100644
> --- a/arch/arm/mach-imx/mm-imx5.c
> +++ b/arch/arm/mach-imx/mm-imx5.c
> @@ -20,26 +20,61 @@
>  
>  #include <mach/hardware.h>
>  #include <mach/common.h>
> +#include <mach/cpuidle.h>
>  #include <mach/devices-common.h>
>  #include <mach/iomux-v3.h>
>  
>  static struct clk *gpc_dvfs_clk;
>  
> -static void imx5_idle(void)
> +static int imx5_idle(void)
>  {
> +	int ret = 0;
> +
>  	/* gpc clock is needed for SRPG */
>  	if (gpc_dvfs_clk == NULL) {
>  		gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");

This clk_get should go away here and be moved somewhere to
initialization. Also, if getting this clock fails we can still
do regular cpu_do_idle. Additionally, if clk_get fails, we'll
have a ERR_PTR value in gpc_dvfs_clk in which case the
gpc_dvfs_clk == NULL won't trigger next time you are here and
then you'll enable a nonexisting clock below.

>  		if (IS_ERR(gpc_dvfs_clk))
> -			return;
> +			return -ENODEV;
>  	}
>  	clk_enable(gpc_dvfs_clk);
>  	mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
>  	if (!tzic_enable_wake())
>  		cpu_do_idle();
> +	else
> +		ret = -EBUSY;
>  	clk_disable(gpc_dvfs_clk);
> +
> +	return ret;
> +}
> +
> +static int imx5_cpuidle_enter(struct cpuidle_device *dev,
> +				struct cpuidle_driver *drv, int idx)
> +{
> +	int ret;
> +
> +	ret = imx5_idle();
> +
> +	if (ret < 0)
> +		return ret;
> +
> +	return idx;
>  }
>  
> +static struct cpuidle_driver imx5_cpuidle_driver = {
> +	.name			= "imx5_cpuidle",
> +	.owner			= THIS_MODULE,
> +	.en_core_tk_irqen	= 1,
> +	.states[0]	= {
> +		.enter			= imx5_cpuidle_enter,
> +		.exit_latency		= 20, /* max latency at 160MHz */
> +		.target_residency	= 1,
> +		.flags			= CPUIDLE_FLAG_TIME_VALID,
> +		.name			= "IMX5 SRPG",
> +		.desc			= "CPU state retained,powered off",
> +	},

I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state.
The above is something different, right? It has a greater exit latency
than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell?

> +	.state_count		= 1,
> +};
> +
>  /*
>   * Define the MX50 memory map.
>   */
> @@ -103,7 +138,7 @@ void __init imx51_init_early(void)
>  	mxc_set_cpu_type(MXC_CPU_MX51);
>  	mxc_iomux_v3_init(MX51_IO_ADDRESS(MX51_IOMUXC_BASE_ADDR));
>  	mxc_arch_reset_init(MX51_IO_ADDRESS(MX51_WDOG1_BASE_ADDR));
> -	arm_pm_idle = imx5_idle;
> +	arm_pm_idle = (void (*)(void))imx5_idle;

Still this looks suspicious. Reading this will lead to the question why
this prototype is casted. Please just add a imx5_pm_idle with the
correct prototype.

>  }
>  
>  void __init imx53_init_early(void)
> @@ -238,4 +273,5 @@ void __init imx53_soc_init(void)
>  void __init imx51_init_late(void)
>  {
>  	mx51_neon_fixup();
> +	imx_cpuidle_init(&imx5_cpuidle_driver);
>  }
> -- 
> 1.7.10
> 
> 

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Re: [PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver

[Rob Lee]

Sascha,

On Wed, May 9, 2012 at 3:02 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Mon, May 07, 2012 at 04:16:46PM -0500, Robert Lee wrote:
>> Add imx5 cpuidle driver.
>>
>> Signed-off-by: Robert Lee <rob.lee@linaro.org>
>> ---
>>  arch/arm/mach-imx/mm-imx5.c |   42 +++++++++++++++++++++++++++++++++++++++---
>>  1 file changed, 39 insertions(+), 3 deletions(-)
>>
>> diff --git a/arch/arm/mach-imx/mm-imx5.c b/arch/arm/mach-imx/mm-imx5.c
>> index d6b7e9f..0b3a4cc 100644
>> --- a/arch/arm/mach-imx/mm-imx5.c
>> +++ b/arch/arm/mach-imx/mm-imx5.c
>> @@ -20,26 +20,61 @@
>>
>>  #include <mach/hardware.h>
>>  #include <mach/common.h>
>> +#include <mach/cpuidle.h>
>>  #include <mach/devices-common.h>
>>  #include <mach/iomux-v3.h>
>>
>>  static struct clk *gpc_dvfs_clk;
>>
>> -static void imx5_idle(void)
>> +static int imx5_idle(void)
>>  {
>> +     int ret = 0;
>> +
>>       /* gpc clock is needed for SRPG */
>>       if (gpc_dvfs_clk == NULL) {
>>               gpc_dvfs_clk = clk_get(NULL, "gpc_dvfs");
>
> This clk_get should go away here and be moved somewhere to
> initialization. Also, if getting this clock fails we can still
> do regular cpu_do_idle. Additionally, if clk_get fails, we'll
> have a ERR_PTR value in gpc_dvfs_clk in which case the
> gpc_dvfs_clk == NULL won't trigger next time you are here and
> then you'll enable a nonexisting clock below.
>

Agree.  I'd prefer to enable this clock during intialization and just
leave it running.  It is supposed to be a very low power clock and I
couldn't measuring any power difference with and without it being
enabled

>>               if (IS_ERR(gpc_dvfs_clk))
>> -                     return;
>> +                     return -ENODEV;
>>       }
>>       clk_enable(gpc_dvfs_clk);
>>       mx5_cpu_lp_set(WAIT_UNCLOCKED_POWER_OFF);
>>       if (!tzic_enable_wake())
>>               cpu_do_idle();
>> +     else
>> +             ret = -EBUSY;
>>       clk_disable(gpc_dvfs_clk);
>> +
>> +     return ret;
>> +}
>> +
>> +static int imx5_cpuidle_enter(struct cpuidle_device *dev,
>> +                             struct cpuidle_driver *drv, int idx)
>> +{
>> +     int ret;
>> +
>> +     ret = imx5_idle();
>> +
>> +     if (ret < 0)
>> +             return ret;
>> +
>> +     return idx;
>>  }
>>
>> +static struct cpuidle_driver imx5_cpuidle_driver = {
>> +     .name                   = "imx5_cpuidle",
>> +     .owner                  = THIS_MODULE,
>> +     .en_core_tk_irqen       = 1,
>> +     .states[0]      = {
>> +             .enter                  = imx5_cpuidle_enter,
>> +             .exit_latency           = 20, /* max latency at 160MHz */
>> +             .target_residency       = 1,
>> +             .flags                  = CPUIDLE_FLAG_TIME_VALID,
>> +             .name                   = "IMX5 SRPG",
>> +             .desc                   = "CPU state retained,powered off",
>> +     },
>
> I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state.
> The above is something different, right? It has a greater exit latency
> than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell?

Yes and no.  Yes this is a different state but no, it doesn't have a
significantly greater exit latency, or at least a large enough exit
latency to warrant an extra state in my opinion.  According to the
i.MX5 documentation, the extra exit time beyond basic WFI required for
the  "WAIT_UNCLOCKED_POWER_OFF" state is 500ns (this is due to a
difference in i.MX5 hardware implementation compared to all other ARM
platforms).  In reality, it did require a few more microseconds to
perform in my testing just based on the extra register writes in
mx5_cpu_lp_set().  I'd like to clean up mx5_cpu_lp_set() and add a
global variable to track the previous state and to just exit out if
the new state is the same as the old.  I could do this cleanup as part
of this patchset if you prefer that.

>
>> +     .state_count            = 1,
>> +};
>> +
>>  /*
>>   * Define the MX50 memory map.
>>   */
>> @@ -103,7 +138,7 @@ void __init imx51_init_early(void)
>>       mxc_set_cpu_type(MXC_CPU_MX51);
>>       mxc_iomux_v3_init(MX51_IO_ADDRESS(MX51_IOMUXC_BASE_ADDR));
>>       mxc_arch_reset_init(MX51_IO_ADDRESS(MX51_WDOG1_BASE_ADDR));
>> -     arm_pm_idle = imx5_idle;
>> +     arm_pm_idle = (void (*)(void))imx5_idle;
>
> Still this looks suspicious. Reading this will lead to the question why
> this prototype is casted. Please just add a imx5_pm_idle with the
> correct prototype.

Ok.

Thanks,
Rob

>
>>  }
>>
>>  void __init imx53_init_early(void)
>> @@ -238,4 +273,5 @@ void __init imx53_soc_init(void)
>>  void __init imx51_init_late(void)
>>  {
>>       mx51_neon_fixup();
>> +     imx_cpuidle_init(&imx5_cpuidle_driver);
>>  }
>> --
>> 1.7.10
>>
>>
>
> --
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
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Re: [PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver

[Sascha Hauer]

On Wed, May 09, 2012 at 09:27:02AM -0500, Rob Lee wrote:
> Sascha,
> 
> >
> > This clk_get should go away here and be moved somewhere to
> > initialization. Also, if getting this clock fails we can still
> > do regular cpu_do_idle. Additionally, if clk_get fails, we'll
> > have a ERR_PTR value in gpc_dvfs_clk in which case the
> > gpc_dvfs_clk == NULL won't trigger next time you are here and
> > then you'll enable a nonexisting clock below.
> >
> 
> Agree.  I'd prefer to enable this clock during intialization and just
> leave it running.  It is supposed to be a very low power clock and I
> couldn't measuring any power difference with and without it being
> enabled

Ok, even better.

> >
> > I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state.
> > The above is something different, right? It has a greater exit latency
> > than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell?
> 
> Yes and no.  Yes this is a different state but no, it doesn't have a
> significantly greater exit latency, or at least a large enough exit
> latency to warrant an extra state in my opinion.  According to the
> i.MX5 documentation, the extra exit time beyond basic WFI required for
> the  "WAIT_UNCLOCKED_POWER_OFF" state is 500ns (this is due to a
> difference in i.MX5 hardware implementation compared to all other ARM
> platforms).  In reality, it did require a few more microseconds to
> perform in my testing just based on the extra register writes in
> mx5_cpu_lp_set().  I'd like to clean up mx5_cpu_lp_set() and add a
> global variable to track the previous state and to just exit out if
> the new state is the same as the old.

Do you think it's worth it? You buy skipping the read with an additional
test.

> I could do this cleanup as part of this patchset if you prefer that.

Yes please. Cleanups before adding new features is always a good reason
to apply a patch series ;)

Sascha

-- 
Pengutronix e.K.                           |                             |
Industrial Linux Solutions                 | http://www.pengutronix.de/  |
Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |

Re: [PATCH v3 2/3] ARM: imx: Add imx5 cpuidle driver

[Rob Lee]

On Thu, May 10, 2012 at 7:41 AM, Sascha Hauer <s.hauer@pengutronix.de> wrote:
> On Wed, May 09, 2012 at 09:27:02AM -0500, Rob Lee wrote:
>> Sascha,
>>
>> >
>> > This clk_get should go away here and be moved somewhere to
>> > initialization. Also, if getting this clock fails we can still
>> > do regular cpu_do_idle. Additionally, if clk_get fails, we'll
>> > have a ERR_PTR value in gpc_dvfs_clk in which case the
>> > gpc_dvfs_clk == NULL won't trigger next time you are here and
>> > then you'll enable a nonexisting clock below.
>> >
>>
>> Agree.  I'd prefer to enable this clock during intialization and just
>> leave it running.  It is supposed to be a very low power clock and I
>> couldn't measuring any power difference with and without it being
>> enabled
>
> Ok, even better.
>
>> >
>> > I wonder why you don't add the default ARM_CPUIDLE_WFI_STATE_PWR state.
>> > The above is something different, right? It has a greater exit latency
>> > than ARM_CPUIDLE_WFI_STATE_PWR, so why don't we add it here aswell?
>>
>> Yes and no.  Yes this is a different state but no, it doesn't have a
>> significantly greater exit latency, or at least a large enough exit
>> latency to warrant an extra state in my opinion.  According to the
>> i.MX5 documentation, the extra exit time beyond basic WFI required for
>> the  "WAIT_UNCLOCKED_POWER_OFF" state is 500ns (this is due to a
>> difference in i.MX5 hardware implementation compared to all other ARM
>> platforms).  In reality, it did require a few more microseconds to
>> perform in my testing just based on the extra register writes in
>> mx5_cpu_lp_set().  I'd like to clean up mx5_cpu_lp_set() and add a
>> global variable to track the previous state and to just exit out if
>> the new state is the same as the old.
>
> Do you think it's worth it? You buy skipping the read with an additional
> test.
>

I'll run some tests to check.

Thanks,
Rob

>> I could do this cleanup as part of this patchset if you prefer that.
>
> Yes please. Cleanups before adding new features is always a good reason
> to apply a patch series ;)
>
> Sascha
>
> --
> Pengutronix e.K.                           |                             |
> Industrial Linux Solutions                 | http://www.pengutronix.de/  |
> Peiner Str. 6-8, 31137 Hildesheim, Germany | Phone: +49-5121-206917-0    |
> Amtsgericht Hildesheim, HRA 2686           | Fax:   +49-5121-206917-5555 |