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drm/i915/hotplug: document the hotplug handling in the driver

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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>
This commit is contained in:
Jani Nikula 2015-07-02 16:05:28 +03:00 committed by Daniel Vetter
parent 3e6da4a9d9
commit 856974a401
2 changed files with 44 additions and 0 deletions
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5
Documentation/DocBook/drm.tmpl
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@ -4044,6 +4044,11 @@ int num_ioctls;</synopsis>
probing, so those sections fully apply.
</para>
</sect2>
<sect2>
<title>Hotplug</title>
!Pdrivers/gpu/drm/i915/intel_hotplug.c Hotplug
!Idrivers/gpu/drm/i915/intel_hotplug.c
</sect2>
<sect2>
<title>High Definition Audio</title>
!Pdrivers/gpu/drm/i915/intel_audio.c High Definition Audio over HDMI and Display Port

39
drivers/gpu/drm/i915/intel_hotplug.c
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@ -29,6 +29,45 @@
#include "i915_drv.h"
#include "intel_drv.h"
/**
* DOC: Hotplug
*
* Simply put, hotplug occurs when a display is connected to or disconnected
* from the system. However, there may be adapters and docking stations and
* Display Port short pulses and MST devices involved, complicating matters.
*
* Hotplug in i915 is handled in many different levels of abstraction.
*
* The platform dependent interrupt handling code in i915_irq.c enables,
* disables, and does preliminary handling of the interrupts. The interrupt
* handlers gather the hotplug detect (HPD) information from relevant registers
* into a platform independent mask of hotplug pins that have fired.
*
* The platform independent interrupt handler intel_hpd_irq_handler() in
* intel_hotplug.c does hotplug irq storm detection and mitigation, and passes
* further processing to appropriate bottom halves (Display Port specific and
* regular hotplug).
*
* The Display Port work function i915_digport_work_func() calls into
* intel_dp_hpd_pulse() via hooks, which handles DP short pulses and DP MST long
* pulses, with failures and non-MST long pulses triggering regular hotplug
* processing on the connector.
*
* The regular hotplug work function i915_hotplug_work_func() calls connector
* detect hooks, and, if connector status changes, triggers sending of hotplug
* uevent to userspace via drm_kms_helper_hotplug_event().
*
* Finally, the userspace is responsible for triggering a modeset upon receiving
* the hotplug uevent, disabling or enabling the crtc as needed.
*
* The hotplug interrupt storm detection and mitigation code keeps track of the
* number of interrupts per hotplug pin per a period of time, and if the number
* of interrupts exceeds a certain threshold, the interrupt is disabled for a
* while before being re-enabled. The intention is to mitigate issues raising
* from broken hardware triggering massive amounts of interrupts and grinding
* the system to a halt.
*/
enum port intel_hpd_pin_to_port(enum hpd_pin pin)
{
switch (pin) {