Re: [PATCH v4] PCI/portdrv: Only disable hotplug interrupts early when needed.

[Lukas Wunner <lukas@wunner.de>]

On Mon, Mar 03, 2025 at 10:36:30AM +0800, Feng Tang wrote:
> There was problem reported by firmware developers that they received
> two PCIe hotplug commands in very short intervals on an ARM server,
> which doesn't comply with PCIe spec, and broke their state machine and
> work flow. According to PCIe 6.1 spec, section 6.7.3.2, software needs
> to wait at least 1 second for the command-complete event, before
> resending the command or sending a new command.
> 
> In the failure case, the first PCIe hotplug command firmware received
> is from get_port_device_capability(), which sends command to disable
> PCIe hotplug interrupts without waiting for its completion, and the
> second command comes from pcie_enable_notification() of pciehp driver,
> which enables hotplug interrupts again.
> 
> One solution is to add the necessary delay after the first command [1],
> while Lukas proposed an optimization that if the pciehp driver will be
> loaded soon and handle the interrupts, then the hotplug and the wait
> are not needed and can be saved, for every root port.
> 
> So fix it by only disabling the hotplug interrupts when pciehp driver
> is not enabled.
> 
> [1]. https://lore.kernel.org/lkml/20250224034500.23024-1-feng.tang@linux.alibaba.com/t/#u
> 
> Fixes: 2bd50dd800b5 ("PCI: PCIe: Disable PCIe port services during port initialization")
> Suggested-by: Lukas Wunner <lukas@wunner.de>
> Signed-off-by: Feng Tang <feng.tang@linux.alibaba.com>

Reviewed-by: Lukas Wunner <lukas@wunner.de>