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[Why] Some monitors perform rapid “autoscan” HPD re‑assertions right after a disconnect or powersaving mode enablement. These appear as a quick disconnect→reconnect with an identical EDID. Since Linux has no HDMI hotplug detection (HPD) filter, these quick reconnects are seen as hotplug events, which can unintentionally wake a system with DPMS off. An example: https://gitlab.freedesktop.org/drm/amd/-/issues/2876 Such 'fake reconnects' are considered when the interval between a disconnect and a connect is within 1500ms (experimentally chosen using several monitors), and the two connections have the same EDID. [How] Implement a time-based debounce mechanism: 1. On HDMI disconnect detection, instead of immediately processing the HPD event, save the current sink and schedule delayed work (default 1500ms) 2. If another HDMI disconnect HPD event arrives during the debounce period, it reschedules the pending work, ensuring only the final state is processed. 3. When the debounce timer expires, re-detect the display and compare the new sink with the cached one using EDID comparison. 4. If sinks match (same EDID), this was a spontaneous HPD toggle: - Update connector state internally - Skip hotplug event to prevent desktop rearrangement If sinks differ, this was a real display change: - Process normally with the hotplug event The debounce delay is configurable via module parameter 'hdmi_hpd_debounce_delay_ms'. Closes: https://gitlab.freedesktop.org/drm/amd/-/issues/2876 Reviewed-by: Sun peng (Leo) Li <sunpeng.li@amd.com> Signed-off-by: Ivan Lipski <ivan.lipski@amd.com> Tested-by: Dan Wheeler <daniel.wheeler@amd.com> Signed-off-by: Alex Deucher <alexander.deucher@amd.com> (cherry picked from commit c918e75e1ed95be76f8e3156a411188f650fe03f)
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 reStructuredText 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.