[U-Boot] u-boot hangs after detecting DDR3 RAM and Flash.

[Stefan Roese]

Hi Prakash,

On Tuesday 04 May 2010 16:21:19 prakash bedge wrote:
> I am facing an error while porting u-boot for my platform because if
> exception error.
> 
> After running the u-boot to detect the DDR and flash u-boot hangs after
> showing the serial console output. In debugger I am seeing PC at 0x00000400
> address which the exception handler vector address.
> 
> But when I modify the below statement in the function int interrupt_init
> (void) in u-boot\lib_ppc\interrupts.c, u-boot continues and I can see the
> u-boot prompt and I am able to run all u-boot commands.
> 
> int interrupt_init (void)
> {
>     int ret;
> 
>     /* call cpu specific function from $(CPU)/interrupts.c */
>     ret = interrupt_init_cpu (&decrementer_count);
> 
>     if (ret)
>         return ret;
> 
>     set_dec (decrementer_count);
> 
> ---    set_msr (get_msr () | MSR_EE);   //Removed this statement.
> ++  set_msr (get_msr ());

By not setting MSR_EE, you will not be able to receive external interrupts, or 
even worse, your timer will most likely not work. Try the "sleep" command.
 
>     return (0);
> }
> 
> It seems that there is an exception error and because of this u-boot hangs.
> But I didn't get any error condition till now.
> 
> If someone has earlier experienced this kind of issue, please share.

One thing I've noticed in other PPC4xx ports as well, is that DDR auto-
calibration (with short memory tests) can lead to exceptions that need to be 
cleared after the DDR is fully configured. Example:

arch/powerpc/cpu/ppc4xx/44x_spd_ddr2.c:

phys_size_t initdram(int board_type)
{
	...

        /*
         * Clear potential errors resulting from auto-calibration.
         * If not done, then we could get an interrupt later on when
         * exceptions are enabled.
         */
        set_mcsr(get_mcsr());


Hard to tell, if you experience the same problem, since we have little 
information about your platform (which DDR3 core is used etc).

Cheers,
Stefan

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