[Skiboot] [PATCH 2/2] pci: Make fast reboot creset PHBs in parallel

[Russell Currey]

On Thu, 2018-02-22 at 11:26 +1100, Michael Neuling wrote:
> In this patch, we added a creset to the fast reboot path:
> 
>   commit a1eba9d29d17ff44fca1293b071023a9fbf4b938
>   Author: Andrew Donnellan <andrew.donnellan at au1.ibm.com>
>   fast-reboot: creset PHBs on fast reboot
> 
> Unfortunately, this does the creset in serial rather than in
> parallel.
> 
> This patch changes the creset on fast reboot to operate in
> parallel. It simplifies the code by abstracting pci_init_slots() so
> that it can be used on boot and fast reboot to perform all the PCI
> retraining.
> 
> This improves fast reboot PCI training on a dual chip P9 from ~12
> seconds down to ~2 seconds. Similar improvements for P8 are achieved
> as well.
> 
> This means the time to download the BOOTKERNEL is the bottleneck for
> fast reboot.
> 
> Signed-off-by: Michael Neuling <mikey at neuling.org>
> 
Reviewed-by: Russell Currey <ruscur at russell.cc>