drm/i915: Add a way to test the modeset done during gpu reset, v3.

Add force_reset_modeset_test as a parameter to force the modeset path during gpu reset.
This allows a IGT test to set the knob and trigger a hang to force the gpu reset,
even on platforms that wouldn't otherwise require it.

Changes since v1:
- Split out fix to separate commit.
Changes since v2:
- This commit is purely about force_reset_modeset_test now.

Signed-off-by: Maarten Lankhorst <maarten.lankhorst@linux.intel.com>
Testcase: drv_hangman.reset-with-forced-modeset
Tested-by: Ville Syrjälä <ville.syrjala@linux.intel.com>
Link: http://patchwork.freedesktop.org/patch/msgid/1470428910-12125-3-git-send-email-ville.syrjala@linux.intel.com
Signed-off-by: Ville Syrjälä <ville.syrjala@linux.intel.com>

3 files changed, 25 insertions, 11 deletions

diff --git a/drivers/gpu/drm/i915/i915_params.c b/drivers/gpu/drm/i915/i915_params.c
index b6e404c91eed..768ad89d9cd4 100644
--- a/drivers/gpu/drm/i915/i915_params.c
+++ b/drivers/gpu/drm/i915/i915_params.c
@@ -45,6 +45,7 @@ struct i915_params i915 __read_mostly = {
         .fastboot = 0,
         .prefault_disable = 0,
         .load_detect_test = 0,
+        .force_reset_modeset_test = 0,
         .reset = true,
         .invert_brightness = 0,
         .disable_display = 0,
@@ -161,6 +162,11 @@ MODULE_PARM_DESC(load_detect_test,
         "Force-enable the VGA load detect code for testing (default:false). "
         "For developers only.");
 
+module_param_named_unsafe(force_reset_modeset_test, i915.force_reset_modeset_test, bool, 0600);
+MODULE_PARM_DESC(force_reset_modeset_test,
+        "Force a modeset during gpu reset for testing (default:false). "
+        "For developers only.");
+
 module_param_named_unsafe(invert_brightness, i915.invert_brightness, int, 0600);
 MODULE_PARM_DESC(invert_brightness,
         "Invert backlight brightness "
diff --git a/drivers/gpu/drm/i915/i915_params.h b/drivers/gpu/drm/i915/i915_params.h
index 0ad020b4a925..3a0dd78ddb38 100644
--- a/drivers/gpu/drm/i915/i915_params.h
+++ b/drivers/gpu/drm/i915/i915_params.h
@@ -57,6 +57,7 @@ struct i915_params {
         bool fastboot;
         bool prefault_disable;
         bool load_detect_test;
+        bool force_reset_modeset_test;
         bool reset;
         bool disable_display;
         bool verbose_state_checks;
diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index a95139575324..8fa200bfc2c1 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -3161,7 +3161,8 @@ void intel_prepare_reset(struct drm_i915_private *dev_priv)
         }
 
         /* reset doesn't touch the display, but flips might get nuked anyway, */
-        if (INTEL_GEN(dev_priv) >= 5 || IS_G4X(dev_priv))
+        if (!i915.force_reset_modeset_test &&
+            (INTEL_GEN(dev_priv) >= 5 || IS_G4X(dev_priv)))
                 return;
 
         /*
@@ -3212,16 +3213,22 @@ void intel_finish_reset(struct drm_i915_private *dev_priv)
 
         /* reset doesn't touch the display */
         if (INTEL_GEN(dev_priv) >= 5 || IS_G4X(dev_priv)) {
-                /*
-                 * Flips in the rings have been nuked by the reset,
-                 * so update the base address of all primary
-                 * planes to the the last fb to make sure we're
-                 * showing the correct fb after a reset.
-                 *
-                 * FIXME: Atomic will make this obsolete since we won't schedule
-                 * CS-based flips (which might get lost in gpu resets) any more.
-                 */
-                intel_update_primary_planes(dev);
+                if (!state) {
+                        /*
+                         * Flips in the rings have been nuked by the reset,
+                         * so update the base address of all primary
+                         * planes to the the last fb to make sure we're
+                         * showing the correct fb after a reset.
+                         *
+                         * FIXME: Atomic will make this obsolete since we won't schedule
+                         * CS-based flips (which might get lost in gpu resets) any more.
+                         */
+                        intel_update_primary_planes(dev);
+                } else {
+                        ret = __intel_display_resume(dev, state);
+                        if (ret)
+                                DRM_ERROR("Restoring old state failed with %i\n", ret);
+                }
         } else {
                 /*
                  * The display has been reset as well,