linux-kernel - Re: [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during reset

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Date:   Tue, 03 Jul 2018 20:42:12 +0530
From:   poza@...eaurora.org
To:     Lukas Wunner <lukas@...ner.de>
Cc:     Sinan Kaya <okaya@...eaurora.org>, linux-pci@...r.kernel.org,
        linux-arm-msm@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        Bjorn Helgaas <bhelgaas@...gle.com>,
        Keith Busch <keith.busch@...el.com>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH V5 3/3] PCI: Mask and unmask hotplug interrupts during
 reset

On 2018-07-03 20:04, Lukas Wunner wrote:
> On Mon, Jul 02, 2018 at 06:52:47PM -0400, Sinan Kaya wrote:
>> @@ -308,8 +310,17 @@ void pcie_do_fatal_recovery(struct pci_dev *dev, 
>> u32 service)
>>  		pci_dev_put(pdev);
>>  	}
>> 
>> +	hpsvc = pcie_port_find_service(udev, PCIE_PORT_SERVICE_HP);
>> +	hpdev = pcie_port_find_device(udev, PCIE_PORT_SERVICE_HP);
>> +
>> +	if (hpdev && hpsvc)
>> +		hpsvc->mask_irq(to_pcie_device(hpdev));
>> +
>>  	result = reset_link(udev, service);
>> 
>> +	if (hpdev && hpsvc)
>> +		hpsvc->unmask_irq(to_pcie_device(hpdev));
>> +
> 
> We've already got the ->reset_slot callback in struct hotplug_slot_ops,
> I'm wondering if we really need additional ones for this use case.
> 
> If you just do...
> 
> 	if (!pci_probe_reset_slot(dev->slot))
> 		pci_reset_slot(dev->slot)
> 	else {
> 		/* regular code path */
> 	}
> 
> would that not be equivalent?
> 

pcie_do_fatal_recovery() calls
           reset_link()
              which calls dpc_reset_link() or aer_root_reset() depending 
on the event.

and dpc_reset_link() and aer_root_reset() do their own cleanup stuffs.
infact, aer_root_reset() is the only function which actually triggers 
pci_reset_bridge_secondary_bus().

So if we try to fit in your suggestion:

if (!pci_probe_reset_slot(dev->slot))
{
     pci_reset_slot(dev->slot)
     result = reset_link(udev, service); >> in this case aer_root_reset 
must not call pci_reset_bridge_secondary_bus()
} else
     result = reset_link(udev, service); >> in this case aer_root_reset 
must call pci_reset_bridge_secondary_bus() [since bridge is not hotplug 
capable)

Did I get your suggestion right ?

Regards,
Oza.

> (It's worth noting though that pciehp is the only hotplug driver
> implementing the ->reset_slot callback.  If hotplug is handled by
> a different driver or by the platform firmware, devices may still
> be removed and re-enumerated twice.)
> 

> Thanks,
> 
> Lukas