Since the workaround for buggy displays that do not reply to
live status detect immediately affects a rather limited set of
displays, and since the price paid (almost 100ms per HDMI-port),
we should have that hack disabled by default.

Rather than leaving people with these kinds of broken displays
out in the cold completely, add a module parameter, defaulting
to -1 (live status detection on supported platforms, but without
the extra delays), that allows for re-enabling this hack.

Signed-off-by: David Weinehall <david.weineh...@linux.intel.com>
---
 drivers/gpu/drm/i915/i915_params.c |  8 ++++++++
 drivers/gpu/drm/i915/i915_params.h |  1 +
 drivers/gpu/drm/i915/intel_hdmi.c  | 20 ++++++++++++++++++--
 3 files changed, 27 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/i915/i915_params.c 
b/drivers/gpu/drm/i915/i915_params.c
index 768ad89d9cd4..ad5988b17656 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -62,6 +62,7 @@ struct i915_params i915 __read_mostly = {
        .inject_load_failure = 0,
        .enable_dpcd_backlight = false,
        .enable_gvt = false,
+       .live_status = -1,
 };
 
 module_param_named(modeset, i915.modeset, int, 0400);
@@ -233,3 +234,10 @@ MODULE_PARM_DESC(enable_dpcd_backlight,
 module_param_named(enable_gvt, i915.enable_gvt, bool, 0400);
 MODULE_PARM_DESC(enable_gvt,
        "Enable support for Intel GVT-g graphics virtualization host 
support(default:false)");
+
+module_param_named(live_status, i915.live_status, int, 0600);
+MODULE_PARM_DESC(live_status,
+       "Enable live status detection "
+       "(-1=auto [default], "
+         "0=disabled, "
+         "1=enabled with extra delay)");
diff --git a/drivers/gpu/drm/i915/i915_params.h 
b/drivers/gpu/drm/i915/i915_params.h
index 3a0dd78ddb38..2ff2083936e3 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -52,6 +52,7 @@ struct i915_params {
        int mmio_debug;
        int edp_vswing;
        unsigned int inject_load_failure;
+       int live_status;
        /* leave bools at the end to not create holes */
        bool enable_hangcheck;
        bool fastboot;
diff --git a/drivers/gpu/drm/i915/intel_hdmi.c 
b/drivers/gpu/drm/i915/intel_hdmi.c
index 713c91ce7f70..b7d88728335a 100644
--- a/drivers/gpu/drm/i915/intel_hdmi.c
+++ b/drivers/gpu/drm/i915/intel_hdmi.c
@@ -1468,6 +1468,7 @@ intel_hdmi_detect(struct drm_connector *connector, bool 
force)
        struct intel_hdmi *intel_hdmi = intel_attached_hdmi(connector);
        struct drm_i915_private *dev_priv = to_i915(connector->dev);
        bool live_status = false;
+       int attempts = 1;
        unsigned int try;
 
        DRM_DEBUG_KMS("[CONNECTOR:%d:%s]\n",
@@ -1478,12 +1479,27 @@ intel_hdmi_detect(struct drm_connector *connector, bool 
force)
        /*
         * Live status register is not reliable on all intel platforms.
         * So consider live_status only for certain platforms, for
-        * others, read EDID to determine presence of sink.
+        * others, read EDID to determine presence of sink, unless
+        * the users explicitly disables live status reads. For users
+        * who have broken displays we offer the option to use
+        * live status with an extra delay.
         */
+       switch (i915.live_status) {
+       case 0:
+               live_status = true;
+               break;
+       case 1:
+               attempts = 9;
+               break;
+       default:
+       case -1:
+               break;
+       }
+
        if (INTEL_INFO(dev_priv)->gen < 7 || IS_IVYBRIDGE(dev_priv))
                live_status = true;
 
-       for (try = 0; !live_status && try < 9; try++) {
+       for (try = 0; !live_status && try < attempts; try++) {
                if (try)
                        msleep(10);
                live_status = intel_digital_port_connected(dev_priv,
-- 
2.8.1

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