On 2018-07-03 17:00, okaya@xxxxxxxxxxxxxx wrote:
On 2018-07-03 04:34, Lukas Wunner wrote:
On Mon, Jul 02, 2018 at 06:52:47PM -0400, Sinan Kaya wrote:
If a bridge supports hotplug and observes a PCIe fatal error, the
following
events happen:
1. AER driver removes the devices from PCI tree on fatal error
2. AER driver brings down the link by issuing a secondary bus reset
waits
for the link to come up.
3. Hotplug driver observes a link down interrupt
4. Hotplug driver tries to remove the devices waiting for the rescan
lock
but devices are already removed by the AER driver and AER driver is
waiting
for the link to come back up.
5. AER driver tries to re-enumerate devices after polling for the
link
state to go up.
6. Hotplug driver obtains the lock and tries to remove the devices
again.
If a bridge is a hotplug capable bridge, mask hotplug interrupts
before the
reset and unmask afterwards.
Would it work for you if you just amended the AER driver to skip
removal and re-enumeration of devices if the port is a hotplug bridge?
Just check for is_hotplug_bridge in struct pci_dev.
The reason why we want to remove devices before secondary bus reset is
to quiesce pcie bus traffic before issuing a reset.
Skipping this step might cause transactions to be lost in the middle
of the reset as there will be active traffic flowing and drivers will
suddenly start reading ffs.
I don't think we can skip this step.
what if we only have conditional enumeration ? (leaving removing
devices followed by SBR as is) ?
following code is doing little more extra work than our normal ERR_FATAL
path.
pciehp_unconfigure_device doing little more than enumeration to
quiescence the bus.
/*
* Ensure that no new Requests will be generated from
* the device.
*/
if (presence) {
pci_read_config_word(dev, PCI_COMMAND, &command);
command &= ~(PCI_COMMAND_MASTER | PCI_COMMAND_SERR);
command |= PCI_COMMAND_INTX_DISABLE;
pci_write_config_word(dev, PCI_COMMAND, command);
}
That would seem like a much simpler solution, given that it is known
that the link will flap on reset, causing the hotplug driver to remove
and re-enumerate devices. That would also cover cases where hotplug
is
handled by a different driver than pciehp, or by the platform
firmware.
Thanks,
Lukas
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