[RFC] 4xx hardware watchpoint support

[Kumar Gala]

On Jul 23, 2008, at 10:53 AM, Josh Boyer wrote:

> On Tue, 22 Jul 2008 22:47:58 -0300
> Luis Machado <luisgpm at linux.vnet.ibm.com> wrote:
>
>> Hi,
>>
>>> That, or adding a small function to move the bits to the appropriate
>>> registers (set_dbcr or set_dac_events).
>>>
>>>> Do you think it's worth to support this facility on 405's  
>>>> processors? If
>>>> so, i'll gladly work on a solution to it.
>>>
>>> I would think so.  There's really no difference from a userspace
>>> perspective, so gdb watchpoints could be valuable there too.  I'll
>>> leave it up to you though.
>>
>> As the 440 support is ready and the 405 needs additional tweaking  
>> due to
>> the use of DBCR1 instead of DBCR0 and due to a different position  
>> scheme
>> of the DAC1R/DAC1W flags inside DBCR1, i'd say we should include this
>> code and handle the 405 case later.
>
> That's fine with me, but I have one question below then.
>
>> Index: linux-2.6.26/arch/powerpc/kernel/signal.c
>> ===================================================================
>> --- linux-2.6.26.orig/arch/powerpc/kernel/signal.c	2008-07-20  
>> 16:56:57.000000000 -0700
>> +++ linux-2.6.26/arch/powerpc/kernel/signal.c	2008-07-22  
>> 16:47:22.000000000 -0700
>> @@ -145,8 +145,12 @@
>> 	 * user space. The DABR will have been cleared if it
>> 	 * triggered inside the kernel.
>> 	 */
>> -	if (current->thread.dabr)
>> +	if (current->thread.dabr) {
>> 		set_dabr(current->thread.dabr);
>> +#if defined(CONFIG_40x) || defined(CONFIG_BOOKE)
>> +		mtspr(SPRN_DBCR0, current->thread.dbcr0);
>> +#endif
>
> Shouldn't this (and other places) be:
>
> #if defined(CONFIG_44x) || defined(CONFIG_BOOKE)
>
> if you are going to exclude 40x for now?  Otherwise this is still
> enabled on 405 and setting the wrong register.

if we are ignoring 40x this can just be CONFIG_BOOKE.  CONFIG_44x sets  
CONFIG_BOOKE.

- k