[#4404] default kernel config selects GENERIC_TIME

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[#4404] default kernel config selects GENERIC_TIME

Submitted By: Graf Yang

Open Date

2008-09-02 23:46:38     Close Date

2009-09-22 00:02:07

Priority:

Low     Assignee:

Graf Yang

Status:

Closed     Fixed In Release:

N/A

Found In Release:

2008R1.5-RC3     Release:

Category:

Kernel Functions     Board:

N/A

Processor:

ALL     Silicon Revision:

Is this bug repeatable?:

Yes     Resolution:

Fixed

Uboot version or rev.:

    Toolchain version or rev.:

any

App binary format:

N/A     

Summary: default kernel config selects GENERIC_TIME

Details:

 

If GENERIC_TIME is selected, the time related system call only get coarse time that based on tick. 2008R1 disabled it on every board.

 

Follow-ups

 

--- Graf Yang                                                2008-09-03 00:30:35

NO_HZ depends on this option, so could not blindly close it.

 

--- Robin Getz                                               2009-01-08 15:09:53

If I understand the description (which I will re-word since I don't understand

the existing description)

 

When GENERIC_TIME is selected (which it is by default for all the ADI boards)

then all time keeping in the kernel has a resolution based on the default clock

source - since we also have GENERIC_CLOCKEVENTS selected - the clock source used

is jiffies -- giving all timing keeping in the kernel a jiffy based resolution.

 

This is as designed - and is working properly -- no bug.

 

To change this behavior:

   a) select CYCLES_CLOCKSOURCE (Which we do not do by default since

      CYCLES/CYCLES2 is writable in userspace)

   b) create a new platform driver for clock source/clock event which

     uses gptimers as a clock source/event

 

I think b) would be a good idea, but it still not a bug.

 

-Robin

 

--- Graf Yang                                                2009-01-09 01:27:15

What I need to do is to create a platform driver for clock source/clock event

which uses core-timer or gptimers. Then user can get more precise time through

sys_gettimeofday().

SMP kernel on BF561 will not boot with this option. (Currently, If SMP is

selected, GENERIC_TIMER will be deselected.) I will make it work when

SMP+GENERIC_TIMER.

 

--- Mike Frysinger                                           2009-01-09 01:45:31

writing a gptimer clocksource platform driver would also be good because we

could enable it by default and always enable GENERIC_TIME/GENERIC_CLOCKEVENTS

(and delete arch/blackfin/kernel/time.c)

 

--- Robin Getz                                               2009-01-09 10:19:18

Yeah, having an option for:

- core timer (CLK domain)

- general purpose timers (SCLK domain)

 

would be great.

 

--- Graf Yang                                                2009-05-20 04:38:02

Now both the core timer and gptimer0 can generate ticks.

Both the cycles and gptimer0 can be the clock source.

 

--- Graf Yang                                                2009-09-22 00:02:07

It has been fixed long time ago, so close it.

 

 

 

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