Re: [PATCH v2 06/10] arm/arm-powerctl: rebuild hflags after setting CP15 bits in arm_set_cpu_on()

[Richard Henderson]

On 12/18/19 11:01 AM, Niek Linnenbank wrote:
> Hello Richard,
> 
> On Tue, Dec 17, 2019 at 5:41 PM Richard Henderson <address@hidden
> <mailto:address@hidden>> wrote:
> 
>     On 12/17/19 6:12 AM, Peter Maydell wrote:
>     > Cc'ing Richard : this is one for you I think... (surely we
>     > need to rebuild the hflags from scratch when we power up
>     > a CPU anyway?)
> 
>     We do compute hflags from scratch in reset.
> 
>     It has also turned out that there were a few board models that poked at 
> the
>     contents of the cpu and needed special help.  Some of that I would imagine
>     would be fixed properly with the multi-phase reset patches, where we could
>     rebuild hflags when *leaving* reset.
> 
>     In arm_set_cpu_on_async_work, we start by resetting the cpu and then start
>     poking at the contents of some system registers.  So, yes, we do need to
>     rebuild after doing that.  Also, I'm not sure how this function should 
> fit into
>     the multi-phase reset future.
> 
> 
> Great, thanks a lot for confirming and clarifying this!
> You mention the multi-phase reset feature, is that going to replace the
> arm_set_cpu_on() functionality?

I don't think so, but I'm not sure.  As I said above, I don't immediately see
how arm_set_cpu_on() will integrate.

In any case, multi-phase reset is still pending, though I believe it is high on
Peter's priority queue for the 5.0 development cycle.


r~