Nouveau - Dec 2019 - [PATCH AUTOSEL 5.4 146/350] drm/nouveau: Don't grab runtime PM refs for HPD IRQs

From: Lyude Paul <lyude at redhat.com>

[ Upstream commit 09e530657e1c982d3dbc5e4302bf9207950c3d0a ]

In order for suspend/resume reprobing to work, we need to be able to
perform sideband communications during suspend/resume, along with
runtime PM suspend/resume. In order to do so, we also need to make sure
that nouveau doesn't bother grabbing a runtime PM reference to do so,
since otherwise we'll start deadlocking runtime PM again.

Note that we weren't able to do this before, because of the DP MST
helpers processing UP requests from topologies in the same context as
drm_dp_mst_hpd_irq() which would have caused us to open ourselves up to
receiving hotplug events and deadlocking with runtime suspend/resume.
Now that those requests are handled asynchronously, this change should
be completely safe.

Cc: Juston Li <juston.li at intel.com>
Cc: Imre Deak <imre.deak at intel.com>
Cc: Ville Syrj?l? <ville.syrjala at linux.intel.com>
Cc: Harry Wentland <hwentlan at amd.com>
Cc: Daniel Vetter <daniel.vetter at ffwll.ch>
Reviewed-by: Ben Skeggs <bskeggs at redhat.com>
Reviewed-by: Sean Paul <sean at poorly.run>
Signed-off-by: Lyude Paul <lyude at redhat.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20191022023641.8026-10-lyude
at redhat.com
Signed-off-by: Sasha Levin <sashal at kernel.org>
---
 drivers/gpu/drm/nouveau/nouveau_connector.c | 33 +++++++++++----------
 1 file changed, 17 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/nouveau/nouveau_connector.c
b/drivers/gpu/drm/nouveau/nouveau_connector.c
index 94dfa2e5a9abe..a442a955f98cb 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -1131,6 +1131,16 @@ nouveau_connector_hotplug(struct nvif_notify *notify)
 	const char *name = connector->name;
 	struct nouveau_encoder *nv_encoder;
 	int ret;
+	bool plugged = (rep->mask != NVIF_NOTIFY_CONN_V0_UNPLUG);
+
+	if (rep->mask & NVIF_NOTIFY_CONN_V0_IRQ) {
+		NV_DEBUG(drm, "service %s\n", name);
+		drm_dp_cec_irq(&nv_connector->aux);
+		if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP)))
+			nv50_mstm_service(nv_encoder->dp.mstm);
+
+		return NVIF_NOTIFY_KEEP;
+	}
 
 	ret = pm_runtime_get(drm->dev->dev);
 	if (ret == 0) {
@@ -1151,25 +1161,16 @@ nouveau_connector_hotplug(struct nvif_notify *notify)
 		return NVIF_NOTIFY_DROP;
 	}
 
-	if (rep->mask & NVIF_NOTIFY_CONN_V0_IRQ) {
-		NV_DEBUG(drm, "service %s\n", name);
-		drm_dp_cec_irq(&nv_connector->aux);
-		if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP)))
-			nv50_mstm_service(nv_encoder->dp.mstm);
-	} else {
-		bool plugged = (rep->mask != NVIF_NOTIFY_CONN_V0_UNPLUG);
-
+	if (!plugged)
+		drm_dp_cec_unset_edid(&nv_connector->aux);
+	NV_DEBUG(drm, "%splugged %s\n", plugged ? "" :
"un", name);
+	if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP))) {
 		if (!plugged)
-			drm_dp_cec_unset_edid(&nv_connector->aux);
-		NV_DEBUG(drm, "%splugged %s\n", plugged ? "" :
"un", name);
-		if ((nv_encoder = find_encoder(connector, DCB_OUTPUT_DP))) {
-			if (!plugged)
-				nv50_mstm_remove(nv_encoder->dp.mstm);
-		}
-
-		drm_helper_hpd_irq_event(connector->dev);
+			nv50_mstm_remove(nv_encoder->dp.mstm);
 	}
 
+	drm_helper_hpd_irq_event(connector->dev);
+
 	pm_runtime_mark_last_busy(drm->dev->dev);
 	pm_runtime_put_autosuspend(drm->dev->dev);
 	return NVIF_NOTIFY_KEEP;
-- 
2.20.1