mainlining shenanigans
9408cc94eb
Once upon a time, hotplugging devices on MST branches actually worked in DRM. Now, it only works in amdgpu (likely because of how it's hotplug handlers are implemented). On both i915 and nouveau, hotplug notifications from MST branches are noticed - but trying to respond to them causes messaging timeouts and causes the whole topology state to go out of sync with reality, usually resulting in the user needing to replug the entire topology in hopes that it actually fixes things. The reason for this is because the way we currently handle UP requests in MST is completely bogus. drm_dp_mst_handle_up_req() is called from drm_dp_mst_hpd_irq(), which is usually called from the driver's hotplug handler. Because we handle sending the hotplug event from this function, we actually cause the driver's hotplug handler (and in turn, all sideband transactions) to block on drm_device->mode_config.connection_mutex. This makes it impossible to send any sideband messages from the driver's connector probing functions, resulting in the aforementioned sideband message timeout. There's even more problems with this beyond breaking hotplugging on MST branch devices. It also makes it almost impossible to protect drm_dp_mst_port struct members under a lock because we then have to worry about dealing with all of the lock dependency issues that ensue. So, let's finally actually fix this issue by handling the processing of up requests asyncronously. This way we can send sideband messages from most contexts without having to deal with getting blocked if we hold connection_mutex. This also fixes MST branch device hotplugging on i915, finally! Cc: Juston Li <juston.li@intel.com> Cc: Imre Deak <imre.deak@intel.com> Cc: Ville Syrjälä <ville.syrjala@linux.intel.com> Cc: Harry Wentland <hwentlan@amd.com> Cc: Daniel Vetter <daniel.vetter@ffwll.ch> Reviewed-by: Sean Paul <sean@poorly.run> Signed-off-by: Lyude Paul <lyude@redhat.com> Link: https://patchwork.freedesktop.org/patch/msgid/20191022023641.8026-5-lyude@redhat.com |
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| include | ||
| init | ||
| ipc | ||
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| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
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| README | ||
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.