Re: [PATCH v7 00/14] PCI: rzg3s-host: Add PCIe hotplug support

[Claudiu Beznea <claudiu.beznea@kernel.org>]

Hi, Wolfram,

On 11/10/26 22:39, Wolfram Sang wrote:
> Hi Claudiu,
> 
> finally, I got around to it...

Thank you for checking this.

> 
>> I currently can't reproduce this on my side. Do you remember if you executed
>> the below command before your test:
>>
>> echo performance > /sys/module/pcie_aspm/parameters/policy
> 
> No, I did not and it makes a difference. With the command above, removal
> also works fine. But leaving it and letting the policy stay "default",
> removal doesn't work. I don't even see this line:
> 
> pcieport 0000:00:00.0: Recovering Root Port due to Link Down
> 
> Is this expected? I'd think "default" should work as well?

What I suspect happens in this particular case is that due to the PCIe link 
being in a power saving state (when ASPM policy is default), and since the RC 
don't have native hotplug support, the RC is unable to see something happened 
with the link and to trigger the link event IRQ. Any subsequent operation that
gets the link out of a power saving mode should  make the HW aware of something 
happened at the link level and trigger the link event IRQ as well.

E.g.: if you keep the ASPM policy to default and generate a link up/down event 
that will not be seen by Linux. A subsequent lspci will trigger it. Steps to 
check this:

1/ Make sure the link up
2/ echo default > /sys/module/pcie_aspm/parameters/policy
3/ trigger link down; at this point Linux should see nothing
4/ run lspci; at this point link IRQ will be generated and Linux will take the
    action to remove the PCIe devices

Thank you,
Claudiu