drm/nouveau/disp/dp: maintain link in response to hpd signal
This previously worked for the most part due to userspace doing a
modeset in response to HPD interrupts. This will allow us to
properly handle cases where sync is lost for other reasons, or if
userspace isn't caring.
Signed-off-by: Ben Skeggs <bskeggs@redhat.com>
diff --git a/drivers/gpu/drm/nouveau/core/engine/disp/nv50.c b/drivers/gpu/drm/nouveau/core/engine/disp/nv50.c
index a73bc15..90974cd 100644
--- a/drivers/gpu/drm/nouveau/core/engine/disp/nv50.c
+++ b/drivers/gpu/drm/nouveau/core/engine/disp/nv50.c
@@ -1457,6 +1457,24 @@
if (!outp)
return;
+ /* we allow both encoder attach and detach operations to occur
+ * within a single supervisor (ie. modeset) sequence. the
+ * encoder detach scripts quite often switch off power to the
+ * lanes, which requires the link to be re-trained.
+ *
+ * this is not generally an issue as the sink "must" (heh)
+ * signal an irq when it's lost sync so the driver can
+ * re-train.
+ *
+ * however, on some boards, if one does not configure at least
+ * the gpu side of the link *before* attaching, then various
+ * things can go horribly wrong (PDISP disappearing from mmio,
+ * third supervisor never happens, etc).
+ *
+ * the solution is simply to retrain here, if necessary. last
+ * i checked, the binary driver userspace does not appear to
+ * trigger this situation (it forces an UPDATE between steps).
+ */
if (outp->info.type == DCB_OUTPUT_DP) {
u32 soff = (ffs(outp->info.or) - 1) * 0x08;
u32 ctrl, datarate;
@@ -1478,7 +1496,8 @@
break;
}
- nouveau_dp_train((void *)outp, datarate / soff);
+ if (nvkm_output_dp_train(outp, datarate / soff, true))
+ ERR("link not trained before attach\n");
}
exec_clkcmp(priv, head, 0, pclk, &conf);