Re: Register Access

Hello

I found a similar problem to Christian's, but using the PWM module from 
the 5329.

I have solved it creating a driver to access the PWM registers from the 
kernel.

But I am yet intrigued by it. I was not able to found why these user 
registers were not accesible from userspace. I am using an old 2.16.17 
uclinux. I revised SCM PACRx registers and they are all filled with 0 
(giving user access, I think). Someone suggested me a cache entry 
restriction, but I only can see SDRAM caching at the start code.

What other thing can limit that access?

Thank you,
Jose



El 24/10/2012 3:38, Greg Ungerer escribió:
> Hi Christian,
>
> On 24/10/12 01:06, Christian Gieseler wrote:
>> We have to activate dithering in our Coldfire 5329 device.  But it 
>> seams,
>> that I cant even read the register values  of PLL Control Register 
>> (PCR) and
>> PLL Modulation Divider Register (PMDR). The registers should be user
>> readable and writable.
>
> Why do you think they should be user space read/write?
>
>
>> But it seems that I get a bus error because the
>> values do not match the written ones or the reset values if I don┤t 
>> write
>> something.
>
> That would seem to indicate that those registers are not user space
> read/write.
>
> Check your settings of the PACRx registers (Peripheral Access Control
> Registers). They power up with the supervisor only access bit set,
> so unless you have changed them you won't get user access.
>
> Regards
> Greg
>
>
>> #define GT_REG_READ_SHORT(Reg, pData)
>> \
>> *pData = ((volatile unsigned short)*((unsigned short *) (Reg)));
>>
>> #define GT_REG_WRITE(Reg, 
>> data)                                          \
>> (*(volatile unsigned long *)(Reg)) =data
>>
>> #define PLL_PODR        0xFC0C0000
>> #define PLL_PLLCR       0xFC0C0004
>> #define PLL_PMDR        0xFC0C0008
>> int main(int argc, char *argv[])
>> {
>> unsigned int RegVal=0;
>>
>>      //GT_REG_WRITE(MCF_PLL_PLLCR,0x0);
>>      GT_REG_WRITE (PLL_PLLCR ,0);
>>         GT_REG_WRITE (PLL_PMDR ,0x5);
>>      //Setze PLL Control Register
>>      GT_REG_WRITE (PLL_PLLCR ,0x87);
>>
>>
>>      GT_REG_READ_SHORT (PLL_PLLCR,(unsigned int*)&RegVal);
>>      printf ("PLLCR has Value=%x\n",RegVal);
>>
>>
>> return 0;
>> }
>>
>> Does someone have a hint how to write and read these registers? Is 
>> something
>> wrong in my code?
>>
>> Best regards
>> Christian
>>
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>
>

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