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

From: Lorenzo Pieralisi
Date: Thu Nov 21 2019 - 11:47:14 EST

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

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.