drm/nouveau/disp: semi-complete link training sequence even if display disappears

Signed-off-by: Ben Skeggs <bskeggs@redhat.com>

1 files changed, 32 insertions, 16 deletions

diff --git a/drivers/gpu/drm/nouveau/core/engine/disp/dport.c b/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
index 15448b9abac8..1bd4c63369c1 100644
--- a/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
+++ b/drivers/gpu/drm/nouveau/core/engine/disp/dport.c
@@ -70,17 +70,10 @@ dp_set_link_config(struct dp_state *dp)
         };
         u32 lnkcmp;
         u8 sink[2];
+        int ret;
 
         DBG("%d lanes at %d KB/s\n", dp->link_nr, dp->link_bw);
 
-        /* set desired link configuration on the sink */
-        sink[0] = dp->link_bw / 27000;
-        sink[1] = dp->link_nr;
-        if (dp->dpcd[DPCD_RC02] & DPCD_RC02_ENHANCED_FRAME_CAP)
-                sink[1] |= DPCD_LC01_ENHANCED_FRAME_EN;
-
-        nv_wraux(dp->aux, DPCD_LC00, sink, 2);
-
         /* set desired link configuration on the source */
         if ((lnkcmp = dp->info.lnkcmp)) {
                 if (dp->version < 0x30) {
@@ -96,10 +89,22 @@ dp_set_link_config(struct dp_state *dp)
                 nvbios_exec(&init);
         }
 
-        return dp->func->lnk_ctl(dp->disp, dp->outp, dp->head,
-                                 dp->link_nr, dp->link_bw / 27000,
-                                 dp->dpcd[DPCD_RC02] &
-                                          DPCD_RC02_ENHANCED_FRAME_CAP);
+        ret = dp->func->lnk_ctl(dp->disp, dp->outp, dp->head,
+                                dp->link_nr, dp->link_bw / 27000,
+                                dp->dpcd[DPCD_RC02] &
+                                         DPCD_RC02_ENHANCED_FRAME_CAP);
+        if (ret) {
+                ERR("lnk_ctl failed with %d\n", ret);
+                return ret;
+        }
+
+        /* set desired link configuration on the sink */
+        sink[0] = dp->link_bw / 27000;
+        sink[1] = dp->link_nr;
+        if (dp->dpcd[DPCD_RC02] & DPCD_RC02_ENHANCED_FRAME_CAP)
+                sink[1] |= DPCD_LC01_ENHANCED_FRAME_EN;
+
+        return nv_wraux(dp->aux, DPCD_LC00, sink, 2);
 }
 
 static void
@@ -294,8 +299,17 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
 
         ret = nv_rdaux(dp->aux, 0x00000, dp->dpcd, sizeof(dp->dpcd));
         if (ret) {
+                /* it's possible the display has been unplugged before we
+                 * get here.  we still need to execute the full set of
+                 * vbios scripts, and program the OR at a high enough
+                 * frequency to satisfy the target mode.  failure to do
+                 * so results at best in an UPDATE hanging, and at worst
+                 * with PDISP running away to join the circus.
+                 */
+                dp->dpcd[1] = link_bw[0] / 27000;
+                dp->dpcd[2] = 4;
+                dp->dpcd[3] = 0x00;
                 ERR("failed to read DPCD\n");
-                return ret;
         }
 
         /* adjust required bandwidth for 8B/10B coding overhead */
@@ -328,8 +342,10 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
                             !dp_link_train_eq(dp))
                                 break;
                 } else
-                if (ret >= 1) {
-                        /* dp_set_link_config() handled training */
+                if (ret) {
+                        /* dp_set_link_config() handled training, or
+                         * we failed to communicate with the sink.
+                         */
                         break;
                 }
 
@@ -344,5 +360,5 @@ nouveau_dp_train(struct nouveau_disp *disp, const struct nouveau_dp_func *func,
 
         /* execute post-train script from vbios */
         dp_link_train_fini(dp);
-        return true;
+        return (ret < 0) ? false : true;
 }