devmem2 question

[Jesse Forgues]

I swear checking registers made sense to me a few weeks ago when I was troubleshooting multichannel audio issues on the McASP but for the last two days I have been stumped how it ever made sense to me! Doh!

I understand that 48038000 is the McASP base address.

When I run: /devmem2 0x48038000

I expected to get: 0x44300A02h

But instead I get:

./devmem2 0x48038000

/dev/mem opened.

Memory mapped at address 0xb6f3a000.

Value at address 0x48038000 (0xb6f3a000): 0x44307B02

Have I been looking at the TRM for too long and need some sleep!!!

From the AM335x TRM it says on page 4597: http://www.ti.com/lit/ug/spruh73k/spruh73k.pdf

22.3.1.1 REV Register (offset = 0h) [reset = 44300A02h]

REV is shown in Figure 22-38 and described in Table 22-9.
The revision identification register (REV) contains identification data for the peripheral.

Figure 22-38. REV Register

LEGEND: R/W = Read/Write; R = Read only; W1toCl = Write 1 to clear bit; -n = value after reset Table 22-9. REV Register Field Descriptions

31302928272625242322212019181716151413121110 9 8 7 6 5 4 3 2 1 0

REV

R-44300A02h

Bit	Field	Type	Reset	Description
31-0	REV	R	44300A02h	Identifies revision of peripheral.

Version of devmem2.c: wget http://sources.buildroot.net/devmem2.c

Build: gcc devmem2.c -o devmem2

[Alfredo Muniz]

On Tue, Jul 1, 2014 at 10:37 AM, Jesse Forgues <jesse...@gmail.com> wrote:

Have I been looking at the TRM for too long and need some sleep!!!

Jesse,

It's just a different revision on the peripheral. I wouldn't let it get to you :)

[Jesse Cobra]

Well I suspect that other registers I check are also incorrect. I'll add some more examples tomorrow...

And that revision is read only, odd it would not match the TRM, yes?

Losing sleep over this question...
;)

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[Alfredo Muniz]

On Tue, Jul 1, 2014 at 7:27 PM, Jesse Cobra <jesse...@gmail.com> wrote:

Well I suspect that other registers I check are also incorrect

Yes some will be incorrect and some will be correct. That is how these things go. You can usually rely on the registers locations though so it shouldn't affect what you are trying to do.