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

[Bjørn Forsman]

2011/1/15 Russell King - ARM Linux <linux at arm.linux.org.uk>:
> On Sat, Jan 15, 2011 at 05:37:08PM +0100, Bjørn Forsman wrote:
>> Hi,
>>
>> On 15 January 2011 02:17, Marek Vasut <marek.vasut at gmail.com> wrote:
>> > Rework of patch from 2009:
>> > PalmZ72: Add support for OV9640 camera sensor
>> >
>> > Signed-off-by: Marek Vasut <marek.vasut at 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,
Bjørn Forsman