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Commit 856974a4 authored by Jani Nikula's avatar Jani Nikula Committed by Daniel Vetter
Browse files

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



Add an overview of the drm/i915 hotplug handling.

Signed-off-by: default avatarJani Nikula <jani.nikula@intel.com>
Signed-off-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
parent 3e6da4a9

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

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) {