DSPLink timing

Bill Loraine

I am interested in timing of the DSPLink. Do you have any timing data, time to process data from the GPP to the DSP for the loop example distributed with the DSPLink software using the OS vxWorks. Actually any timing data would be better then what I have, which is nothing. I would like to know the time that it takes on the GPP from the start of write CHNL_issue command to the return of the CHNL_reclaim command. Also the write issue to reclaim timing for the DSP

over 14 years ago

judahvang over 14 years ago

TI__Mastermind 32475 points

Bill,

DSPLink is a legacy product at this point, but I'll look to see if I can find any timing data for it.

Judah

judahvang over 14 years ago in reply to judahvang

TI__Mastermind 32475 points

Bill,

Can you take a look here http://processors.wiki.ti.com/index.php/DSPLink_FAQs to see if you can find the answer you are looking for?

Judah

Bill Loraine over 14 years ago in reply to judahvang

Prodigy 30 points

judahvang,

There was the following: But the function to update is at path $(DSPLINK)/gpp/src/osal/Linux/2.6.18/dpc.c

I am using vxworks and the DPC.c file in vxworks does not contain the function DPC_callback referenced below. I believe that the DPC_callback function is a Linux function and is not used for vxWorkshe path to the source code is for Linux.

I didn't see any others

Does DSPLink work in an Real Time environment? When I use it I see high latency?

Yes, DSPLink is RT safe. It works in an RT environment. However the performance may be slow as DSPLink internal threads can be pre-empted by the RT threads.

If you want to enable the DSPLink threads to work in a RT environment, you can update the DSPLink threads to the RT scheduling policy. See below for reference code.

Update function at path $(DSPLINK)/gpp/src/osal/Linux/2.6.18/dpc.c

DPC_Callback (void * arg)
{
    Uint32            index = (Uint32)arg ;
 
    TRC_1ENTER ("DPC_Callback", arg) ;
 
 
    /* Set scheduling policy to enable RT */
    <add_code_here>
 
 
    /* Set a high priority to simulate tasklet */
    /* Comment below line */
    /* set_user_nice (current, -10) ; */
…
…
}

Some customers have seen issues with the default throttle limit which ensures that 5% CPU is reserved for non RT threads. To ensure that application and DSPLink RT threads are not pre-empted by the default throttle limit.

“echo -1 > /proc/sys/kernel/sched_rt_runtime_us”

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DSPLink timing