drm/i915: Break encoder->crtc link separately in intel_sanitize_crtc()

Depending on the SDVO output_flags SDVO may have multiple connectors
linking to the same encoder (in intel_connector->encoder->base).
Only one of those connectors should be active (ie link to the encoder
thru drm_connector->encoder).
If intel_connector_break_all_links() is called from intel_sanitize_crtc()
we may break the crtc connection of an encoder thru an inactive connector
in which case intel_connector_break_all_links() will not be called again
for the active connector if this happens to come later in the list due to:
    if (connector->encoder->base.crtc != &crtc->base)
                                 continue;
in intel_sanitize_crtc().
This will however leave the drm_connector->encoder linkage for this
active connector in place. Subsequently this will cause multiple
warnings in intel_connector_check_state() to trigger and the driver
will eventually die in drm_encoder_crtc_ok() (because of crtc == NULL).

To avoid this remove intel_connector_break_all_links() and move its
code to its two calling functions: intel_sanitize_crtc() and
intel_sanitize_encoder().
This allows to implement the link breaking more flexibly matching
the surrounding code: ie. in intel_sanitize_crtc() we can break the
crtc link separatly after the links to the encoders have been
broken which avoids above problem.

This regression has been introduced in:

commit 24929352481f085c5f85d4d4cbc919ddf106d381
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Mon Jul 2 20:28:59 2012 +0200

    drm/i915: read out the modeset hw state at load and resume time

so goes back to the very beginning of the modeset rework.

v2: This patch takes care of the concernes voiced by Chris Wilson
and Daniel Vetter that only breaking links if the drm_connector
is linked to an encoder may miss some links.
v3: move all encoder handling to encoder loop as suggested by
Daniel Vetter.

Signed-off-by: Egbert Eich <eich@suse.de>
Reviewed-by: Daniel Vetter <daniel.vetter@ffwll.ch>
Cc: stable@vger.kernel.org
Cc: Jani Nikula <jani.nikula@linux.intel.com>
Signed-off-by: Jani Nikula <jani.nikula@intel.com>

1 files changed, 14 insertions, 12 deletions

diff --git a/drivers/gpu/drm/i915/intel_display.c b/drivers/gpu/drm/i915/intel_display.c
index 69bcc42a0e44..48aa516a1ac0 100644
--- a/drivers/gpu/drm/i915/intel_display.c
+++ b/drivers/gpu/drm/i915/intel_display.c
@@ -11395,15 +11395,6 @@ void intel_modeset_init(struct drm_device *dev)
         }
 }
 
-static void
-intel_connector_break_all_links(struct intel_connector *connector)
-{
-        connector->base.dpms = DRM_MODE_DPMS_OFF;
-        connector->base.encoder = NULL;
-        connector->encoder->connectors_active = false;
-        connector->encoder->base.crtc = NULL;
-}
-
 static void intel_enable_pipe_a(struct drm_device *dev)
 {
         struct intel_connector *connector;
@@ -11485,8 +11476,17 @@ static void intel_sanitize_crtc(struct intel_crtc *crtc)
                         if (connector->encoder->base.crtc != &crtc->base)
                                 continue;
 
-                        intel_connector_break_all_links(connector);
+                        connector->base.dpms = DRM_MODE_DPMS_OFF;
+                        connector->base.encoder = NULL;
                 }
+                /* multiple connectors may have the same encoder:
+                 *  handle them and break crtc link separately */
+                list_for_each_entry(connector, &dev->mode_config.connector_list,
+                                    base.head)
+                        if (connector->encoder->base.crtc == &crtc->base) {
+                                connector->encoder->base.crtc = NULL;
+                                connector->encoder->connectors_active = false;
+                        }
 
                 WARN_ON(crtc->active);
                 crtc->base.enabled = false;
@@ -11568,6 +11568,8 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
                                       drm_get_encoder_name(&encoder->base));
                         encoder->disable(encoder);
                 }
+                encoder->base.crtc = NULL;
+                encoder->connectors_active = false;
 
                 /* Inconsistent output/port/pipe state happens presumably due to
                  * a bug in one of the get_hw_state functions. Or someplace else
@@ -11578,8 +11580,8 @@ static void intel_sanitize_encoder(struct intel_encoder *encoder)
                                     base.head) {
                         if (connector->encoder != encoder)
                                 continue;
-
-                        intel_connector_break_all_links(connector);
+                        connector->base.dpms = DRM_MODE_DPMS_OFF;
+                        connector->base.encoder = NULL;
                 }
         }
         /* Enabled encoders without active connectors will be fixed in