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[ Upstream commite8afd0d9fc] If a PCIe hotplug slot has an Attention Button, the normal hot-add flow is: - Slot is empty and slot power is off - User inserts card in slot and presses Attention Button - OS blinks Power Indicator for 5 seconds - After 5 seconds, OS turns on Power Indicator, turns on slot power, and enumerates the device Previously, if a user pressed the Attention Button on an *empty* slot, pciehp logged the following messages and blinked the Power Indicator until a second button press: [0.000] pciehp: Button press: will power on in 5 sec [0.001] # Power Indicator starts blinking [5.001] # 5 second timeout; slot is empty, so we should cancel the request to power on and turn off Power Indicator [7.000] # Power Indicator still blinking [8.000] # possible card insertion [9.000] pciehp: Button press: canceling request to power on The first button press incorrectly left the slot in BLINKINGON_STATE, so the second was interpreted as a "cancel power on" event regardless of whether a card was present. If the slot is empty, turn off the Power Indicator and return from BLINKINGON_STATE to OFF_STATE after 5 seconds, effectively canceling the request to power on. Putting the slot in OFF_STATE also means the second button press will correctly request a slot power on if the slot is occupied. [bhelgaas: commit log] Link: https://lore.kernel.org/r/20230512021518.336460-1-clementwei90@163.com Fixes:d331710ea7("PCI: pciehp: Become resilient to missed events") Suggested-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Rongguang Wei <weirongguang@kylinos.cn> Signed-off-by: Bjorn Helgaas <bhelgaas@google.com> Reviewed-by: Lukas Wunner <lukas@wunner.de> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.