[ELDK] R: R: Userland memory access

[Detlev Zundel]

Hi Luigi,

> I'm using a TMQ885D board with kernel 2.4.25. 

Wow, applied archeology ;)

> In the driver, mapping this external SRAM with a simple ioremap and using
> the returned pointer, I'm able to access the memory without problems:
>
> 		
> 	dp_mem_base = ioremap(0x90000000, 0x80000);	
>
> 	// write and read first location in SRAM
> 	*((unsigned long*)dp_mem_base) = 0x11223344;	
> 	value = *((unsigned long*)dp_mem_base); 	

Ok.

> Now, I would like to access my External SRAM this way also from user-land.
> Basically in the mmap entry point I call: 
>
> remap_page_range(vma->vm_start, 0x90000000, 0x80000, vma->vm_page_prot)

As far as I can tell (2.4 is a long time ago), this seems ok.  I assume
you still did setup a correct mapping with ioremap() before, correct?

> And in my application:
>
> ptr_mem = mmap(0,0x80000,(PROT_READ|PROT_WRITE),MAP_SHARED,DP_Fd,0);

Also looks ok.

> But in this case, when I try to use ptr_mem pointer to write directly in
> SRAM, I have always  an "EMT trap" with no kernel log. 
> Reading things are just a little bit different: sometimes I have the correct
> values and  sometimes I have some errors like "EMT trap" or "Floating
> exception" with log:
>
> Bad emulation writemem/34
>  NIP: 0fef6e60 instruction: 9421ff70 opcode: 25 A: 1 B: 1f C: 1d code: 3b8
> rc: 0
>  pte @ 0x fef6e60:  (0xc7bc80fc)->(0xc7b94bd8)->0x07e36889
>  RPN: 07e36 PP: 2 SPS: 1 SH: 0 CI: 0 v: 1
> Kernel VA for NIP 0xc7e36e60  pte @ 0xc7e36e60: no pmd
> ttyS: 1 input overrun(s)
> Close IDT70V659 module.

Hm, are you sure that you did the ioremap() in the driver?

Cheers
  Detlev

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