How OMAP-L138 and RT OS (Linux) share timers?

VIDAL Damien

Other Parts Discussed in Thread: OMAP-L138, OMAPL138

Dear Community,

I am a hardware designer, and I am interfacing, for my specific application, the module manufactured by LOGIC called “OMAP-L138_SOM”. My application is running on Linux and should use a lot of timers and functions. I cannot find a document that explains how Linux uses the resources (especially timers) of the OMAP-L138 processor. I will try to explain more the problem:

· My application use the watchdog (Timer1 of the processor)

· My application use the RTC (Timer0 of the processor)

· I don’t know if Linux need to use timers? Other?

I want to guarantee that Linux kernel is not using the same resource that the application and that the resources are sufficient for every need of my configurations.

Example of bad case:

Application: Three 64 Bit General-purpose timers and One 64-Bit General-Purpose Timer (Watch dog)

Linux:

My conclusion: The maximum timers resources are used by the application, I think that is not possible to run Linux.

Does any document exist to explain how Linux kernel uses OMAP-L138 processor?

Does any document exist to explain how to configure Linux kernel use of OMAP-L138 timers?

Thanks,

Damien VIDAL

over 14 years ago

0 dabuan over 14 years ago

TI__Genius 14545 points

Vidal,

I'm not not a Linux expert, so I don't have an answer for you, but I've notified a linux expert to respond to this tread. They should reply shortly.

0 Loc Truong over 14 years ago in reply to dabuan

TI__Intellectual 2620 points

There's a wiki page describing what Linux implementation for OMAPL138 is using at http://processors.wiki.ti.com/index.php/OMAP-L1_Linux_Drivers_Usage#Timers

If you want to see in detail how the Linux clock system is implemented for OMAPL138 (and most DaVinci SoCs), browse to source files <sdk path>/psp/<linux kernel version>/arch/arm/mach-davinci/time.c and the structure da850_clks[] in the file da850.c (in same folder).

0 VIDAL Damien over 14 years ago in reply to Loc Truong

Prodigy 110 points

Dear support,

@Drew: thanks to have transmit my question to the appropriate person

@Loc: thanks’ for your answer; I find every data I was looking for with a very precise detail level.

If I have well understood:

In my application, if I want to use the RTC (Timer0 of the processor), I have to change the Linux kernel configuration to work with Timer2 or 3 (instead of Timer0) to manage ‘clockevent’ and ‘free-run counter’, that’s right?

Many thanks,

Damien VIDAL

0 dabuan over 14 years ago in reply to VIDAL Damien

TI__Genius 14545 points

Damien,

I'm moving this thread to the Linux Forum as it now pertains to Linux configuration. If you have further questions on the the silicon level, please feel free to post another thread with the appropriate subject.

0 VIDAL Damien over 14 years ago in reply to dabuan

Prodigy 110 points

Dear community,

Everyone can confirm or not the following feeling ?

Many thanks,

Damien VIDAL

0 Loc Truong over 14 years ago in reply to VIDAL Damien

TI__Intellectual 2620 points

On OMAP-L138 the Real Time Clock is a separate peripheral. There's no need to change timer 0 to use as RTC.

0 VIDAL Damien over 14 years ago in reply to Loc Truong

Prodigy 110 points

Loc,

When I ask my question, I was sure that the only timer to use for the RTC was Timer0.
I tried to find where I have read that, but without result. I think I misunderstand something.

Thanks to have help me to understand!

Damien

0 Loc Truong over 14 years ago in reply to VIDAL Damien

TI__Intellectual 2620 points

No worries. Wading through this sea of manuals can be intimidating. In case it may help, besides the data manual, you can use the "Peripherals Overview Reference Guide" SPRUFK9C as the catch all manual. Each section for the peripheral will give you the lit number (and URL) for that peripheral's UG. Timer is SPRUFM5 while RTC is SPRUFM3.

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How OMAP-L138 and RT OS (Linux) share timers?