Re-enable link configurations after sink capabilities change or the link
got reset before updating the link capabilities (due to an RX_CAP_CHANGED
HPD IRQ for the currently connected sink, or a new sink getting
connected).

This makes resetting the link explicitly by calling
intel_dp_link_caps_reset() subsequently redundant; keep the existing
behavior wrt. this for now, adding only a TODO: to remove the explicit
reset.

While at it add documentation for intel_dp_link_caps_update().

Signed-off-by: Imre Deak <[email protected]>
---
 drivers/gpu/drm/i915/display/intel_dp.c       |  8 +++-
 .../gpu/drm/i915/display/intel_dp_link_caps.c | 37 +++++++++++++++++--
 .../gpu/drm/i915/display/intel_dp_link_caps.h |  3 +-
 3 files changed, 43 insertions(+), 5 deletions(-)

diff --git a/drivers/gpu/drm/i915/display/intel_dp.c 
b/drivers/gpu/drm/i915/display/intel_dp.c
index 6e3fa6662cbef..23001541283b4 100644
--- a/drivers/gpu/drm/i915/display/intel_dp.c
+++ b/drivers/gpu/drm/i915/display/intel_dp.c
@@ -701,7 +701,8 @@ static bool intel_dp_set_common_link_params(struct intel_dp 
*intel_dp)
        intel_dp_get_common_rates(intel_dp, common_rates, &num_common_rates);
        if (intel_dp_link_caps_update(intel_dp->link.caps,
                                      common_rates, num_common_rates,
-                                     
intel_dp_get_max_common_lane_count(intel_dp)))
+                                     
intel_dp_get_max_common_lane_count(intel_dp),
+                                     intel_dp->reset_link_params))
                params_changed = true;
 
        return params_changed;
@@ -3652,6 +3653,11 @@ void intel_dp_set_link_params(struct intel_dp *intel_dp,
 
 void intel_dp_reset_link_params(struct intel_dp *intel_dp)
 {
+       /*
+        * TODO: Remove the following reset of link capabilities, as
+        * this isn't needed after intel_dp_link_caps_update(reset=true)
+        * was called.
+        */
        intel_dp_link_caps_reset(intel_dp->link.caps);
        intel_dp->link.mst_probed_lane_count = 0;
        intel_dp->link.mst_probed_rate = 0;
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_caps.c 
b/drivers/gpu/drm/i915/display/intel_dp_link_caps.c
index 667d2e55cea19..de520bd423d59 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_caps.c
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_caps.c
@@ -709,14 +709,42 @@ static int link_config_cmp_by_lane_rate(const void *a, 
const void *b, const void
        return lce_a->link_rate_idx - lce_b->link_rate_idx;
 }
 
-/* Return %true if the supported link parameters have changed. */
+/**
+ * intel_dp_link_caps_update - rebuild the supported link configuration state
+ * @link_caps: link capabilities state
+ * @rates: supported common link rates
+ * @num_rates: number of entries in @rates
+ * @max_lane_count: supported maximum lane count
+ * @reset: reset limits and disabled configs
+ *
+ * Rebuild the supported link configuration state from @rates and
+ * @max_lane_count.
+ *
+ * If @reset is %true, reset the maximum link limits to the maximum
+ * supported rate and lane count, and re-enable all configurations.
+ *
+ * This function is called regularly, at least after a sink is connected,
+ * but it may also be called later whenever the sink capabilities may have
+ * changed, for example in response to HPD IRQ / RX_CAP_CHANGED signaling.
+ *
+ * In the Intel driver this function is currently called whenever the
+ * connector detect handler runs, after reading the sink capabilities. This
+ * may change if those capabilities are cached until the sink is
+ * disconnected, or until RX_CAP_CHANGED is signaled. In any case, this
+ * function should be called whenever the sink capabilities were read out
+ * and may have changed.
+ *
+ * Returns:
+ * - %true if the link capabilities have changed, %false otherwise.
+ */
 bool intel_dp_link_caps_update(struct intel_dp_link_caps *link_caps,
-                              const int *rates, int num_rates, int 
max_lane_count)
+                              const int *rates, int num_rates, int 
max_lane_count,
+                              bool reset)
 {
        struct intel_dp *intel_dp = link_caps->dp;
        struct intel_display *display = to_intel_display(intel_dp);
        struct intel_dp_link_config_entry *lce;
-       bool link_params_changed = false;
+       bool link_params_changed = reset;
        int num_common_lane_configs;
        int i;
        int j;
@@ -778,6 +806,9 @@ bool intel_dp_link_caps_update(struct intel_dp_link_caps 
*link_caps,
               link_config_cmp_by_lane_rate, NULL,
               link_caps);
 
+       if (link_params_changed)
+               reset_max_link_limits_reenable_all(link_caps);
+
        return link_params_changed;
 }
 
diff --git a/drivers/gpu/drm/i915/display/intel_dp_link_caps.h 
b/drivers/gpu/drm/i915/display/intel_dp_link_caps.h
index 79aca74ad9eee..dcbde890809bc 100644
--- a/drivers/gpu/drm/i915/display/intel_dp_link_caps.h
+++ b/drivers/gpu/drm/i915/display/intel_dp_link_caps.h
@@ -147,7 +147,8 @@ bool intel_dp_link_caps_set_max_limits(struct 
intel_dp_link_caps *link_caps,
 void intel_dp_link_caps_reset_max_limits(struct intel_dp_link_caps *link_caps);
 
 bool intel_dp_link_caps_update(struct intel_dp_link_caps *link_caps,
-                              const int *rates, int num_rates, int 
max_lane_count);
+                              const int *rates, int num_rates, int 
max_lane_count,
+                              bool reset);
 void intel_dp_link_caps_reset(struct intel_dp_link_caps *link_caps);
 
 void intel_dp_link_caps_debugfs_add(struct intel_connector *connector);
-- 
2.49.1

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