Re: [PATCH 2/2] PCI: uniphier: Add checking whether PERST# is deasserted

[Lorenzo Pieralisi]

On Fri, Nov 08, 2019 at 04:30:27PM +0900, Kunihiko Hayashi wrote:
> > However, If I understand correctly, doesn't your solution only work some
> > of the time? What happens if you boot both machines at the same time,
> > and PERST# isn't asserted prior to the kernel booting?
> 
> I think it contains an annoying problem.
> 
> If PERST# isn't toggled prior to the kernel booting, PERST# remains asserted
> and the RC driver can't access PCI bus.
> 
> As a result, this patch works and deasserts PERST# (and EP configuration will
> be lost). So boot sequence needs to include deasserting PERST#.

I am sorry but I have lost you. Can you explain to us why checking
that PERST# is deasserted guarantees you that:

- The EP has bootstrapped
- It is safe not to toggle it again (and also skip
  uniphier_pcie_ltssm_enable())

Please provide details of the HW configuration so that we understand
what's actually supposed to happen and why this patch fixes the
issue you are facing.

Thanks,
Lorenzo