Reg. virtual address space in embedded linux

[David H. Lynch Jr.]

    Is there a reason you need to map and unmap physical/virtual memory
every time you do a read or write ?

    I think the norm is to map the physical region in your device driver
in its initialization code and unmap it if the driver exits.

    After that you should be able to read and write your chip as you
wish. If the registers are RW then you should be able to "dump" them by
    reading them at whatever later time you choose.


jagannathanjay at aim.com wrote:
> Hi all
>
> We are porting third party driver code from vxworks to Embedded linux
> in MPC 8260 under a evaluation platform from Embedded Planet in linux
> kernel space.
>
> The first step we carried out was reading the chip id and we were able
> to read the chip id correctly.
>  
> For reading the chip id we used the routine ChipReadMemory in the
> attached text and we were able to retrive the chip id successfully.
>  
> Subsequently when we write and read from Chip Specific Control Status
> registers ,it didn't work.
>  
> I checked the manual and the Chip Specific Control Status registers
> have RW access.
>  
> Any inputs on how to check if the write we made to virtual address
> succeeds?
>  
> Is there a way to dump the linux virtual address and examine the write
> we made ?
>
> Regards
> Jay
>
>  
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>
> int ChipReadMemory(unsigned int arg_phys_addr,unsigned int *memValue)
> {
>   void  *virt_addr = NULL;
>   unsigned int phys_addr = 0;
>
>   phys_addr =  DEVICE_BASE_ADDRESS + arg_phys_addr;
>   virt_addr = ioremap(phys_addr, 4);
>   if(virt_addr == NULL)
>   {
>      printk("ChipReadMemory: unable to perform ioremap \n");
>      return -1;
>   }
>   *memValue  = readl(virt_addr);
>     iounmap(virt_addr);
>     return 0;
> }
>
>
> int ChipWriteMemory(unsigned int arg_phys_addr, unsigned int arg_val)
> {
>   void  *virt_addr = NULL;
>   unsigned int phys_addr = 0;
>   phys_addr =  DEVICE_BASE_ADDRESS + arg_phys_addr;
>   virt_addr = ioremap(phys_addr, 4);
>   if(virt_addr == NULL)
>   {
>      printk("ChipWriteMemory : unable to perform ioremap \n");
>      return -1;
>   }
>   writel(arg_val,virt_addr);
>   iounmap(virt_addr);
>    return 0;
> }
>   
> ------------------------------------------------------------------------
>
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-- 
Dave Lynch 					  	    DLA Systems
Software Development:  				         Embedded Linux
717.627.3770 	       dhlii at dlasys.net 	  http://www.dlasys.net
fax: 1.253.369.9244 			           Cell: 1.717.587.7774
Over 25 years' experience in platforms, languages, and technologies too numerous to list.

"Any intelligent fool can make things bigger and more complex... It takes a touch of genius - and a lot of courage to move in the opposite direction."
Albert Einstein

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