linux-kernel - [PATCH v5 09/14] drm/nouveau: Don't grab runtime PM refs for HPD IRQs

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Message-Id: <20191022023641.8026-10-lyude@redhat.com>
Date:   Mon, 21 Oct 2019 22:36:04 -0400
From:   Lyude Paul <lyude@...hat.com>
To:     dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
        nouveau@...ts.freedesktop.org, intel-gfx@...ts.freedesktop.org
Cc:     Juston Li <juston.li@...el.com>, Imre Deak <imre.deak@...el.com>,
        Ville Syrjälä 
        <ville.syrjala@...ux.intel.com>, Harry Wentland <hwentlan@....com>,
        Daniel Vetter <daniel.vetter@...ll.ch>,
        Sean Paul <sean@...rly.run>, Ben Skeggs <bskeggs@...hat.com>,
        David Airlie <airlied@...ux.ie>,
        Daniel Vetter <daniel@...ll.ch>, linux-kernel@...r.kernel.org
Subject: [PATCH v5 09/14] drm/nouveau: Don't grab runtime PM refs for HPD IRQs

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@...el.com>
Cc: Imre Deak <imre.deak@...el.com>
Cc: Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc: Harry Wentland <hwentlan@....com>
Cc: Daniel Vetter <daniel.vetter@...ll.ch>
Reviewed-by: Sean Paul <sean@...rly.run>
Signed-off-by: Lyude Paul <lyude@...hat.com>
---
 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 3a5db17bc5c7..5b413588b823 100644
--- a/drivers/gpu/drm/nouveau/nouveau_connector.c
+++ b/drivers/gpu/drm/nouveau/nouveau_connector.c
@@ -1130,6 +1130,16 @@ 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) {
@@ -1150,25 +1160,16 @@ 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;
-- 
2.21.0