P-Series中的主题 Re: Accessing timer registers in P4080DS

Accessing timer registers in P4080DS

rahul011189 — Fri, 11 Mar 2016 09:46:57 GMT

Hi there,

I am trying to use a timer for profiling my bare-metal code on P4080DS but I couldn't find much info on it.

The e500mc Core reference manual says that there are timers like TB which can be configured and used. However, it does not have much info on using them. There is a small code snippet but it is in assembly language:

It will be helpful if I can get either of the two:

1) A code snippet (in C) which shows how to configure and read/write the timer registers.

2) A code snippet on how to embed the above assembly code in my C code.

TIA,

- Rahul

Re: Accessing timer registers in P4080DS

bpe — Fri, 11 Mar 2016 10:36:11 GMT

Your processor core timer facilities are fully described in EREF_RM, Chapter 6. As of reference code, see how it is

implemented in Linux kernel, function get_tb():

Linux/arch/powerpc/include/asm/time.h - Linux Cross Reference - Free Electrons

Have a great day,
Platon

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Re: Accessing timer registers in P4080DS

rahul011189 — Fri, 11 Mar 2016 15:22:03 GMT

Hi Platon,

In get_tb(), the value seems to be read from the location 0x3dd:

asm volatile("mfspr %0, 0x3dd" : "=r" (tbl));

Where is it specified that TBL register is mapped to 0x3dd? The programmers manual does say that TBL is SPR268 but I am unable to locate the mapping to 0x3dd.

It will be really helpful if you can point me to the a document which clarifies this.

Regards,

Rahul