Re: [PATCH v2] PCI: aardvark: Wait for endpoint to be ready before training link

From: Thomas Petazzoni
Date: Mon Oct 14 2019 - 15:29:56 EST

Hello Remi,

On Wed, 22 May 2019 23:33:50 +0200
Remi Pommarel <repk@xxxxxxxxxxxx> wrote:

> When configuring pcie reset pin from gpio (e.g. initially set by
> u-boot) to pcie function this pin goes low for a brief moment
> asserting the PERST# signal. Thus connected device enters fundamental
> reset process and link configuration can only begin after a minimal
> 100ms delay (see [1]).
> Because the pin configuration comes from the "default" pinctrl it is
> implicitly configured before the probe callback is called:
> driver_probe_device()
> really_probe()
> ...
> pinctrl_bind_pins() /* Here pin goes from gpio to PCIE reset
> function and PERST# is asserted */
> ...
> drv->probe()
> [1] "PCI Express Base Specification", REV. 4.0
> PCI Express, February 19 2014, 6.6.1 Conventional Reset
> Signed-off-by: Remi Pommarel <repk@xxxxxxxxxxxx>

It is always a bit annoying to add another 100ms in the boot path, but
I don't see an easy alternative solution, so:

Acked-by: Thomas Petazzoni <thomas.petazzoni@xxxxxxxxxxx>

Thomas Petazzoni, CTO, Bootlin
Embedded Linux and Kernel engineering