Re: [PATCH] malta4kec hang in calibrate_delay fix

[Nigel Stephens <nigel@mips.com>]

Thiemo Seufer wrote:
> Kevin D. Kissell wrote:
>   
>>> ??? 2007-09-04?????? 12:03 +0200???Kevin D. Kissell?????????
>>>       
>>>> The 4KEc is a MIPS32 Release 2 processor, for which the implementation
>>>> of the Cause.TI bit (bit 30) is required.  You may have a defective board
>>>> or a bad FPGA bitfile.  Please work with your support contacts at MIPS
>>>> to verify that this is not the case.  It may also be that there's something more
>>>> subtle going on in the interrupt processing, such that the Cause.TI bit is being
>>>> cleared before it can be sampled by the code you've changed.  But while the
>>>> patch below presumably solves the symptoms of your problem, I really
>>>> don't think that a kernel hack based on detecting CoreFPA3 is an appropriate
>>>> solution.  I work every day with Malta/CoreFPGA3 bitfiles and have not
>>>> seen Cause.TI fail to function in any of the Release 2 core bitfiles I've used.
>>>>         
>>> My board's core is Release 1 core. So Cause.TI bit always is zero. Maybe
>>> I need update this patch to reflect this, i.e add #ifdef to distinguish
>>> Release 1 and Release 2. Thanks.
>>>       
>> In that case, your core is a 4Kc and not a 4KEc.
>>     
>
> Not quite true, early revisions of the 4KEc were only release 1. This
> seems to be a bug in arch/mips/cpu-probe.c:
>
> static inline void cpu_probe_mips(struct cpuinfo_mips *c)
> {
>         decode_configs(c);
>         switch (c->processor_id & 0xff00) {
>         case PRID_IMP_4KC:
>                 c->cputype = CPU_4KC;
>                 break;
>         case PRID_IMP_4KEC:
>                 c->cputype = CPU_4KEC;
>                 break;
>         case PRID_IMP_4KECR2:
>                 c->cputype = CPU_4KEC;
>                 break;
> 	...
>
> The type for PRID_IMP_4KEC should be CPU_4KC.
>
>   

Maybe the probing code should read the ISA revision level from the AR 
bits (12:10) of the Config0 register to figure out which revision of the 
ISA is implemented.

Nigel