[Skiboot] [PATCH RFC 2/2] phb4: Use ASB for read/writes to PHB registers on resets

[Guilherme G. Piccoli]

On 10/03/2017 10:50 AM, Benjamin Herrenschmidt wrote:
> On Mon, 2017-10-02 at 19:23 -0300, Guilherme G. Piccoli wrote:
>> If we are performing a PHB reset and coming for a bad situation,
>> (and PHB is fenced), we fail because we don't use ASB by default
>> in the phb4_init_hw().
>>
>> This patch makes use of this trick when we are resetting PHBs
>> to workaround possible problems in PHB (aka it might be fenced)
>> and at least try to perform the complete initialization.
>>
>> This proved useful in kdump kernel boot on POWER9 (wspoon).
> 
> We should never be calling init_hw while fenced. If we do then the bug
> is elsewhere. The reset code should be checking for fences already and
> clearing them if needed.

Thanks for your good review, I'll forget about this path, since it's
just "hiding" the issue, and follow your suggestions!

Thanks,


Guilherme