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drm/i915/hotplug: document the hotplug handling in the driver
Add an overview of the drm/i915 hotplug handling. Signed-off-by: Jani Nikula <jani.nikula@intel.com> Signed-off-by: Daniel Vetter <daniel.vetter@ffwll.ch>
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@ -4044,6 +4044,11 @@ int num_ioctls;</synopsis>
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probing, so those sections fully apply.
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probing, so those sections fully apply.
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</para>
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</para>
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</sect2>
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</sect2>
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<sect2>
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<title>Hotplug</title>
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!Pdrivers/gpu/drm/i915/intel_hotplug.c Hotplug
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!Idrivers/gpu/drm/i915/intel_hotplug.c
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</sect2>
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<sect2>
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<sect2>
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<title>High Definition Audio</title>
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<title>High Definition Audio</title>
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!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
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!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port
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@ -29,6 +29,45 @@
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#include "i915_drv.h"
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#include "i915_drv.h"
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#include "intel_drv.h"
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#include "intel_drv.h"
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/**
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* DOC: Hotplug
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*
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* Simply put, hotplug occurs when a display is connected to or disconnected
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* from the system. However, there may be adapters and docking stations and
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* Display Port short pulses and MST devices involved, complicating matters.
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*
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* Hotplug in i915 is handled in many different levels of abstraction.
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*
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* The platform dependent interrupt handling code in i915_irq.c enables,
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* disables, and does preliminary handling of the interrupts. The interrupt
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* handlers gather the hotplug detect (HPD) information from relevant registers
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* into a platform independent mask of hotplug pins that have fired.
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*
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* The platform independent interrupt handler intel_hpd_irq_handler() in
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* intel_hotplug.c does hotplug irq storm detection and mitigation, and passes
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* further processing to appropriate bottom halves (Display Port specific and
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* regular hotplug).
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*
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* The Display Port work function i915_digport_work_func() calls into
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* intel_dp_hpd_pulse() via hooks, which handles DP short pulses and DP MST long
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* pulses, with failures and non-MST long pulses triggering regular hotplug
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* processing on the connector.
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*
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* The regular hotplug work function i915_hotplug_work_func() calls connector
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* detect hooks, and, if connector status changes, triggers sending of hotplug
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* uevent to userspace via drm_kms_helper_hotplug_event().
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*
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* Finally, the userspace is responsible for triggering a modeset upon receiving
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* the hotplug uevent, disabling or enabling the crtc as needed.
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*
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* The hotplug interrupt storm detection and mitigation code keeps track of the
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* number of interrupts per hotplug pin per a period of time, and if the number
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* of interrupts exceeds a certain threshold, the interrupt is disabled for a
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* while before being re-enabled. The intention is to mitigate issues raising
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* from broken hardware triggering massive amounts of interrupts and grinding
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* the system to a halt.
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*/
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enum port intel_hpd_pin_to_port(enum hpd_pin pin)
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enum port intel_hpd_pin_to_port(enum hpd_pin pin)
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{
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{
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switch (pin) {
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switch (pin) {
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