[PATCHv2 for soc 3/4] arm: Add v7_invalidate_l1 to cache-v7.S

[Russell King - ARM Linux]

On Fri, Feb 01, 2013 at 05:14:11PM +0530, Santosh Shilimkar wrote:
> On Friday 01 February 2013 05:02 PM, Russell King - ARM Linux wrote:
>> On Fri, Feb 01, 2013 at 04:59:44PM +0530, Santosh Shilimkar wrote:
>>> Now since we are moving the code under common place, probably we should
>>> update this a function a bit so that it invalidates the CPU cache till
>>> line of unification. Just to be consistent with other flush API.
>>
>> Hmm.  Do you really want a CPU being brought up to do that to the PoU,
>> every time that it is brought up?  I thought you wanted to get rid of
>> that kind of stuff from the hotplug paths so that a CPU being brought
>> up/taken down doesn't affect the caches for the other CPUs within the
>> inner sharable domain.
>>
> You are right. We already git rid of the flush of all cache levels
> in hotplug and wakeup paths and now it is restricted till the PoU.
>
> Assuming for the current v7 machines, PoU is L2, invalidating the cache
> *till* PoU means only CPU local cache. So the API will in a way
> invalidate only local cache.

Err, you want to _invalidate_ the caches down to the point of I/D/TLB
unification?  Are you really sure you want to do that on a system
here other CPUs are running?

Even going down to the LoUIS, that point is the point at which the
_other_ CPUs may be sharing caches.

And invalidating those caches while the other CPUs are running on
secondary CPU startup will be VERY VERY VERY bad.