[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Marek Vasut]

Rework of patch from 2009:
PalmZ72: Add support for OV9640 camera sensor

Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
---
v2: Use gpio_request_array()/gpio_free_array() array

 arch/arm/mach-pxa/include/mach/palmz72.h |    5 +
 arch/arm/mach-pxa/palmz72.c              |  127 ++++++++++++++++++++++++++++++
 2 files changed, 132 insertions(+), 0 deletions(-)

diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h b/arch/arm/mach-pxa/include/mach/palmz72.h
index 2bbcf70..0d4700a 100644
--- a/arch/arm/mach-pxa/include/mach/palmz72.h
+++ b/arch/arm/mach-pxa/include/mach/palmz72.h
@@ -44,6 +44,11 @@
 #define GPIO_NR_PALMZ72_BT_POWER		17
 #define GPIO_NR_PALMZ72_BT_RESET		83
 
+/* Camera */
+#define GPIO_NR_PALMZ72_CAM_PWDN		56
+#define GPIO_NR_PALMZ72_CAM_RESET		57
+#define GPIO_NR_PALMZ72_CAM_POWER		91
+
 /** Initial values **/
 
 /* Battery */
diff --git a/arch/arm/mach-pxa/palmz72.c b/arch/arm/mach-pxa/palmz72.c
index 7bf4017..27a8e6d 100644
--- a/arch/arm/mach-pxa/palmz72.c
+++ b/arch/arm/mach-pxa/palmz72.c
@@ -30,6 +30,7 @@
 #include <linux/wm97xx.h>
 #include <linux/power_supply.h>
 #include <linux/usb/gpio_vbus.h>
+#include <linux/i2c-gpio.h>
 
 #include <asm/mach-types.h>
 #include <asm/mach/arch.h>
@@ -47,6 +48,9 @@
 #include <mach/palm27x.h>
 
 #include <mach/pm.h>
+#include <mach/camera.h>
+
+#include <media/soc_camera.h>
 
 #include "generic.h"
 #include "devices.h"
@@ -103,6 +107,28 @@ static unsigned long palmz72_pin_config[] __initdata = {
 	GPIO22_GPIO,	/* LCD border color */
 	GPIO96_GPIO,	/* lcd power */
 
+	/* PXA Camera */
+	GPIO81_CIF_DD_0,
+	GPIO48_CIF_DD_5,
+	GPIO50_CIF_DD_3,
+	GPIO51_CIF_DD_2,
+	GPIO52_CIF_DD_4,
+	GPIO53_CIF_MCLK,
+	GPIO54_CIF_PCLK,
+	GPIO55_CIF_DD_1,
+	GPIO84_CIF_FV,
+	GPIO85_CIF_LV,
+	GPIO93_CIF_DD_6,
+	GPIO108_CIF_DD_7,
+
+	GPIO56_GPIO,	/* OV9640 Powerdown */
+	GPIO57_GPIO,	/* OV9640 Reset */
+	GPIO91_GPIO,	/* OV9640 Power */
+
+	/* I2C */
+	GPIO117_GPIO,	/* I2C_SCL */
+	GPIO118_GPIO,	/* I2C_SDA */
+
 	/* Misc. */
 	GPIO0_GPIO	| WAKEUP_ON_LEVEL_HIGH,	/* power detect */
 	GPIO88_GPIO,				/* green led */
@@ -254,6 +280,106 @@ device_initcall(palmz72_pm_init);
 #endif
 
 /******************************************************************************
+ * SoC Camera
+ ******************************************************************************/
+#if defined(CONFIG_SOC_CAMERA_OV9640) || \
+	defined(CONFIG_SOC_CAMERA_OV9640_MODULE)
+static struct pxacamera_platform_data palmz72_pxacamera_platform_data = {
+	.flags		= PXA_CAMERA_MASTER | PXA_CAMERA_DATAWIDTH_8 |
+			PXA_CAMERA_PCLK_EN | PXA_CAMERA_MCLK_EN,
+	.mclk_10khz	= 2600,
+};
+
+/* Board I2C devices. */
+static struct i2c_board_info palmz72_i2c_device[] = {
+	{
+		I2C_BOARD_INFO("ov9640", 0x30),
+	}
+};
+
+static int palmz72_camera_power(struct device *dev, int power)
+{
+	gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
+	mdelay(50);
+	return 0;
+}
+
+static int palmz72_camera_reset(struct device *dev)
+{
+	gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
+	mdelay(50);
+	gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
+	mdelay(50);
+	return 0;
+}
+
+static struct soc_camera_link palmz72_iclink = {
+	.bus_id		= 0, /* Match id in pxa27x_device_camera in device.c */
+	.board_info	= &palmz72_i2c_device[0],
+	.i2c_adapter_id	= 0,
+	.module_name	= "ov96xx",
+	.power		= &palmz72_camera_power,
+	.reset		= &palmz72_camera_reset,
+	.flags		= SOCAM_DATAWIDTH_8,
+};
+
+static struct i2c_gpio_platform_data palmz72_i2c_bus_data = {
+	.sda_pin	= 118,
+	.scl_pin	= 117,
+	.udelay		= 10,
+	.timeout	= 100,
+};
+
+static struct platform_device palmz72_i2c_bus_device = {
+	.name		= "i2c-gpio",
+	.id		= 0, /* we use this as a replacement for i2c-pxa */
+	.dev		= {
+		.platform_data	= &palmz72_i2c_bus_data,
+	}
+};
+
+static struct platform_device palmz72_camera = {
+	.name	= "soc-camera-pdrv",
+	.id	= -1,
+	.dev	= {
+		.platform_data	= &palmz72_iclink,
+	},
+};
+
+/* Here we request the camera GPIOs and configure them. We power up the camera
+ * module, deassert the reset pin, but put it into powerdown (low to no power
+ * consumption) mode. This allows us to later bring the module up fast. */
+static struct gpio palmz72_camera_gpios[] = {
+	{ GPIO_NR_PALMZ72_CAM_POWER,	GPIOF_INIT_HIGH,"Camera DVDD" },
+	{ GPIO_NR_PALMZ72_CAM_RESET,	GPIOF_INIT_LOW,	"Camera RESET" },
+	{ GPIO_NR_PALMZ72_CAM_PWDN,	GPIOF_INIT_LOW,	"Camera PWDN" },
+};
+
+static inline void __init palmz72_cam_gpio_init(void)
+{
+	int ret;
+
+	ret = gpio_request_array(ARRAY_AND_SIZE(palmz72_camera_gpios));
+	if (!ret)
+		gpio_free_array(ARRAY_AND_SIZE(palmz72_camera_gpios));
+	else
+		printk(KERN_ERR "Camera GPIO init failed!\n");
+
+	return;
+}
+
+static void __init palmz72_camera_init(void)
+{
+	palmz72_cam_gpio_init();
+	pxa_set_camera_info(&palmz72_pxacamera_platform_data);
+	platform_device_register(&palmz72_i2c_bus_device);
+	platform_device_register(&palmz72_camera);
+}
+#else
+static inline void palmz72_camera_init(void) {}
+#endif
+
+/******************************************************************************
  * Machine init
  ******************************************************************************/
 static void __init palmz72_init(void)
@@ -276,6 +402,7 @@ static void __init palmz72_init(void)
 	palm27x_pmic_init();
 	palmz72_kpc_init();
 	palmz72_leds_init();
+	palmz72_camera_init();
 }
 
 MACHINE_START(PALMZ72, "Palm Zire72")
-- 
1.7.2.3

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Bjørn Forsman]

Hi,

On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
> Rework of patch from 2009:
> PalmZ72: Add support for OV9640 camera sensor
>
> Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
> ---
> v2: Use gpio_request_array()/gpio_free_array() array
>
> ?arch/arm/mach-pxa/include/mach/palmz72.h | ? ?5 +
> ?arch/arm/mach-pxa/palmz72.c ? ? ? ? ? ? ?| ?127 ++++++++++++++++++++++++++++++
> ?2 files changed, 132 insertions(+), 0 deletions(-)
>
> diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h b/arch/arm/mach-pxa/include/mach/palmz72.h
> index 2bbcf70..0d4700a 100644
> --- a/arch/arm/mach-pxa/include/mach/palmz72.h
> +++ b/arch/arm/mach-pxa/include/mach/palmz72.h

[snip]

> +static int palmz72_camera_power(struct device *dev, int power)
> +{
> + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
> + ? ? ? mdelay(50);
> + ? ? ? return 0;
> +}
> +
> +static int palmz72_camera_reset(struct device *dev)
> +{
> + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
> + ? ? ? mdelay(50);
> + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
> + ? ? ? mdelay(50);
> + ? ? ? return 0;
> +}

(Sorry if these are stupid newbie-questions.)

Is the entire kernel blocked during the above mdelay()s or
just some kernel thread? (Or: will this add like 100ms or 150ms
to boot time?)

Can mdelay() be replaced with something non-blocking?

[snip]

Best regards,
Bj?rn Forsman

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Russell King - ARM Linux]

On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bj?rn Forsman wrote:
> Hi,
> 
> On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
> > Rework of patch from 2009:
> > PalmZ72: Add support for OV9640 camera sensor
> >
> > Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
> > ---
> > v2: Use gpio_request_array()/gpio_free_array() array
> >
> > ?arch/arm/mach-pxa/include/mach/palmz72.h | ? ?5 +
> > ?arch/arm/mach-pxa/palmz72.c ? ? ? ? ? ? ?| ?127 ++++++++++++++++++++++++++++++
> > ?2 files changed, 132 insertions(+), 0 deletions(-)
> >
> > diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h b/arch/arm/mach-pxa/include/mach/palmz72.h
> > index 2bbcf70..0d4700a 100644
> > --- a/arch/arm/mach-pxa/include/mach/palmz72.h
> > +++ b/arch/arm/mach-pxa/include/mach/palmz72.h
> 
> [snip]
> 
> > +static int palmz72_camera_power(struct device *dev, int power)
> > +{
> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
> > + ? ? ? mdelay(50);
> > + ? ? ? return 0;
> > +}
> > +
> > +static int palmz72_camera_reset(struct device *dev)
> > +{
> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
> > + ? ? ? mdelay(50);
> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
> > + ? ? ? mdelay(50);
> > + ? ? ? return 0;
> > +}
> 
> (Sorry if these are stupid newbie-questions.)
> 
> Is the entire kernel blocked during the above mdelay()s or
> just some kernel thread? (Or: will this add like 100ms or 150ms
> to boot time?)
> 
> Can mdelay() be replaced with something non-blocking?

mdelay() is a spinning delay - it doesn't voluntarily relinquish the
CPU to another task.

If you have preempt enabled and the region is preemptable, you can be
preempted in the middle of the delay (in which case it becomes delay
time + time away from the thread.)

msleep() can be used for places where you can sleep, but is limited to
the jiffy granularity for !HIRES kernels.

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Bjørn Forsman]

2011/1/15 Russell King - ARM Linux <linux@arm.linux.org.uk>:
> On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bj?rn Forsman wrote:
>> Hi,
>>
>> On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
>> > Rework of patch from 2009:
>> > PalmZ72: Add support for OV9640 camera sensor
>> >
>> > Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
>> > ---
>> > v2: Use gpio_request_array()/gpio_free_array() array
>> >
>> > ?arch/arm/mach-pxa/include/mach/palmz72.h | ? ?5 +
>> > ?arch/arm/mach-pxa/palmz72.c ? ? ? ? ? ? ?| ?127 ++++++++++++++++++++++++++++++
>> > ?2 files changed, 132 insertions(+), 0 deletions(-)
>> >
>> > diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h b/arch/arm/mach-pxa/include/mach/palmz72.h
>> > index 2bbcf70..0d4700a 100644
>> > --- a/arch/arm/mach-pxa/include/mach/palmz72.h
>> > +++ b/arch/arm/mach-pxa/include/mach/palmz72.h
>>
>> [snip]
>>
>> > +static int palmz72_camera_power(struct device *dev, int power)
>> > +{
>> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
>> > + ? ? ? mdelay(50);
>> > + ? ? ? return 0;
>> > +}
>> > +
>> > +static int palmz72_camera_reset(struct device *dev)
>> > +{
>> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
>> > + ? ? ? mdelay(50);
>> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
>> > + ? ? ? mdelay(50);
>> > + ? ? ? return 0;
>> > +}
>>
>> (Sorry if these are stupid newbie-questions.)
>>
>> Is the entire kernel blocked during the above mdelay()s or
>> just some kernel thread? (Or: will this add like 100ms or 150ms
>> to boot time?)
>>
>> Can mdelay() be replaced with something non-blocking?
>
> mdelay() is a spinning delay - it doesn't voluntarily relinquish the
> CPU to another task.
>
> If you have preempt enabled and the region is preemptable, you can be
> preempted in the middle of the delay (in which case it becomes delay
> time + time away from the thread.)
>
> msleep() can be used for places where you can sleep, but is limited to
> the jiffy granularity for !HIRES kernels.

Thanks for explaining!

Marek, care to try msleep() so we avoid busy-waits?

Best regards,
Bj?rn Forsman

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Marek Vasut]

On Saturday 15 January 2011 18:49:16 Bj?rn Forsman wrote:
> 2011/1/15 Russell King - ARM Linux <linux@arm.linux.org.uk>:
> > On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bj?rn Forsman wrote:
> >> Hi,
> >> 
> >> On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
> >> > Rework of patch from 2009:
> >> > PalmZ72: Add support for OV9640 camera sensor
> >> > 
> >> > Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
> >> > ---
> >> > v2: Use gpio_request_array()/gpio_free_array() array
> >> > 
> >> >  arch/arm/mach-pxa/include/mach/palmz72.h |    5 +
> >> >  arch/arm/mach-pxa/palmz72.c              |  127
> >> > ++++++++++++++++++++++++++++++ 2 files changed, 132 insertions(+), 0
> >> > deletions(-)
> >> > 
> >> > diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h
> >> > b/arch/arm/mach-pxa/include/mach/palmz72.h index 2bbcf70..0d4700a
> >> > 100644
> >> > --- a/arch/arm/mach-pxa/include/mach/palmz72.h
> >> > +++ b/arch/arm/mach-pxa/include/mach/palmz72.h
> >> 
> >> [snip]
> >> 
> >> > +static int palmz72_camera_power(struct device *dev, int power)
> >> > +{
> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
> >> > +       mdelay(50);
> >> > +       return 0;
> >> > +}
> >> > +
> >> > +static int palmz72_camera_reset(struct device *dev)
> >> > +{
> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
> >> > +       mdelay(50);
> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
> >> > +       mdelay(50);
> >> > +       return 0;
> >> > +}
> >> 
> >> (Sorry if these are stupid newbie-questions.)
> >> 
> >> Is the entire kernel blocked during the above mdelay()s or
> >> just some kernel thread? (Or: will this add like 100ms or 150ms
> >> to boot time?)
> >> 
> >> Can mdelay() be replaced with something non-blocking?
> > 
> > mdelay() is a spinning delay - it doesn't voluntarily relinquish the
> > CPU to another task.
> > 
> > If you have preempt enabled and the region is preemptable, you can be
> > preempted in the middle of the delay (in which case it becomes delay
> > time + time away from the thread.)
> > 
> > msleep() can be used for places where you can sleep, but is limited to
> > the jiffy granularity for !HIRES kernels.
> 
> Thanks for explaining!
> 
> Marek, care to try msleep() so we avoid busy-waits?

Let's keep it at mdelay() for now, can we? I'll send a subsequent patch once I 
can test with msleep() ... I don't have the hardware available now.

Cheers

> 
> Best regards,
> Bj?rn Forsman

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Bjørn Forsman]

2011/1/15 Marek Vasut <marek.vasut@gmail.com>:
> On Saturday 15 January 2011 18:49:16 Bj?rn Forsman wrote:
>> 2011/1/15 Russell King - ARM Linux <linux@arm.linux.org.uk>:
>> > On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bj?rn Forsman wrote:
>> >> Hi,
>> >>
>> >> On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
>> >> > Rework of patch from 2009:
>> >> > PalmZ72: Add support for OV9640 camera sensor
>> >> >
>> >> > Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
>> >> > ---
>> >> > v2: Use gpio_request_array()/gpio_free_array() array
>> >> >
>> >> > ?arch/arm/mach-pxa/include/mach/palmz72.h | ? ?5 +
>> >> > ?arch/arm/mach-pxa/palmz72.c ? ? ? ? ? ? ?| ?127
>> >> > ++++++++++++++++++++++++++++++ 2 files changed, 132 insertions(+), 0
>> >> > deletions(-)
>> >> >
>> >> > diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h
>> >> > b/arch/arm/mach-pxa/include/mach/palmz72.h index 2bbcf70..0d4700a
>> >> > 100644
>> >> > --- a/arch/arm/mach-pxa/include/mach/palmz72.h
>> >> > +++ b/arch/arm/mach-pxa/include/mach/palmz72.h
>> >>
>> >> [snip]
>> >>
>> >> > +static int palmz72_camera_power(struct device *dev, int power)
>> >> > +{
>> >> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
>> >> > + ? ? ? mdelay(50);
>> >> > + ? ? ? return 0;
>> >> > +}
>> >> > +
>> >> > +static int palmz72_camera_reset(struct device *dev)
>> >> > +{
>> >> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
>> >> > + ? ? ? mdelay(50);
>> >> > + ? ? ? gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
>> >> > + ? ? ? mdelay(50);
>> >> > + ? ? ? return 0;
>> >> > +}
>> >>
>> >> (Sorry if these are stupid newbie-questions.)
>> >>
>> >> Is the entire kernel blocked during the above mdelay()s or
>> >> just some kernel thread? (Or: will this add like 100ms or 150ms
>> >> to boot time?)
>> >>
>> >> Can mdelay() be replaced with something non-blocking?
>> >
>> > mdelay() is a spinning delay - it doesn't voluntarily relinquish the
>> > CPU to another task.
>> >
>> > If you have preempt enabled and the region is preemptable, you can be
>> > preempted in the middle of the delay (in which case it becomes delay
>> > time + time away from the thread.)
>> >
>> > msleep() can be used for places where you can sleep, but is limited to
>> > the jiffy granularity for !HIRES kernels.
>>
>> Thanks for explaining!
>>
>> Marek, care to try msleep() so we avoid busy-waits?
>
> Let's keep it at mdelay() for now, can we? I'll send a subsequent patch once I
> can test with msleep() ... I don't have the hardware available now.

Sure. It was only a suggestion :-)

Best regards,
Bj?rn Forsman

[PATCH v2] ARM: pxa: PalmZ72: Add OV9640 camera support

[Marek Vasut]

On Saturday 15 January 2011 19:58:39 Bj?rn Forsman wrote:
> 2011/1/15 Marek Vasut <marek.vasut@gmail.com>:
> > On Saturday 15 January 2011 18:49:16 Bj?rn Forsman wrote:
> >> 2011/1/15 Russell King - ARM Linux <linux@arm.linux.org.uk>:
> >> > On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bj?rn Forsman wrote:
> >> >> Hi,
> >> >> 
> >> >> On 15 January 2011 02:17, Marek Vasut <marek.vasut@gmail.com> wrote:
> >> >> > Rework of patch from 2009:
> >> >> > PalmZ72: Add support for OV9640 camera sensor
> >> >> > 
> >> >> > Signed-off-by: Marek Vasut <marek.vasut@gmail.com>
> >> >> > ---
> >> >> > v2: Use gpio_request_array()/gpio_free_array() array
> >> >> > 
> >> >> >  arch/arm/mach-pxa/include/mach/palmz72.h |    5 +
> >> >> >  arch/arm/mach-pxa/palmz72.c              |  127
> >> >> > ++++++++++++++++++++++++++++++ 2 files changed, 132 insertions(+),
> >> >> > 0 deletions(-)
> >> >> > 
> >> >> > diff --git a/arch/arm/mach-pxa/include/mach/palmz72.h
> >> >> > b/arch/arm/mach-pxa/include/mach/palmz72.h index 2bbcf70..0d4700a
> >> >> > 100644
> >> >> > --- a/arch/arm/mach-pxa/include/mach/palmz72.h
> >> >> > +++ b/arch/arm/mach-pxa/include/mach/palmz72.h
> >> >> 
> >> >> [snip]
> >> >> 
> >> >> > +static int palmz72_camera_power(struct device *dev, int power)
> >> >> > +{
> >> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_PWDN, !power);
> >> >> > +       mdelay(50);
> >> >> > +       return 0;
> >> >> > +}
> >> >> > +
> >> >> > +static int palmz72_camera_reset(struct device *dev)
> >> >> > +{
> >> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 1);
> >> >> > +       mdelay(50);
> >> >> > +       gpio_set_value(GPIO_NR_PALMZ72_CAM_RESET, 0);
> >> >> > +       mdelay(50);
> >> >> > +       return 0;
> >> >> > +}
> >> >> 
> >> >> (Sorry if these are stupid newbie-questions.)
> >> >> 
> >> >> Is the entire kernel blocked during the above mdelay()s or
> >> >> just some kernel thread? (Or: will this add like 100ms or 150ms
> >> >> to boot time?)
> >> >> 
> >> >> Can mdelay() be replaced with something non-blocking?
> >> > 
> >> > mdelay() is a spinning delay - it doesn't voluntarily relinquish the
> >> > CPU to another task.
> >> > 
> >> > If you have preempt enabled and the region is preemptable, you can be
> >> > preempted in the middle of the delay (in which case it becomes delay
> >> > time + time away from the thread.)
> >> > 
> >> > msleep() can be used for places where you can sleep, but is limited to
> >> > the jiffy granularity for !HIRES kernels.
> >> 
> >> Thanks for explaining!
> >> 
> >> Marek, care to try msleep() so we avoid busy-waits?
> > 
> > Let's keep it at mdelay() for now, can we? I'll send a subsequent patch
> > once I can test with msleep() ... I don't have the hardware available
> > now.
> 
> Sure. It was only a suggestion :-)

It's actually very valid, I'll keep that in mind :)
> 
> Best regards,
> Bj?rn Forsman