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From: Sean Anderson <sean.anderson@linux.dev>
To: Laurent Pinchart <laurent.pinchart@ideasonboard.com>,
	Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
	Maxime Ripard <mripard@kernel.org>,
	Thomas Zimmermann <tzimmermann@suse.de>,
	dri-devel@lists.freedesktop.org
Cc: David Airlie <airlied@gmail.com>,
	linux-kernel@vger.kernel.org,
	Michal Simek <michal.simek@amd.com>,
	linux-arm-kernel@lists.infradead.org,
	Daniel Vetter <daniel@ffwll.ch>,
	Sean Anderson <sean.anderson@linux.dev>
Subject: [PATCH 3/6] drm: zynqmp_dp: Add locking
Date: Fri, 15 Mar 2024 19:09:13 -0400
Message-Id: <20240315230916.1759060-4-sean.anderson@linux.dev>
In-Reply-To: <20240315230916.1759060-1-sean.anderson@linux.dev>
References: <20240315230916.1759060-1-sean.anderson@linux.dev>
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Add some locking, since none is provided by the drm subsystem. This will
prevent the IRQ/workers/bridge API calls from stepping on each other's
toes.

Signed-off-by: Sean Anderson <sean.anderson@linux.dev>
---

 drivers/gpu/drm/xlnx/zynqmp_dp.c | 59 +++++++++++++++++++++++---------
 1 file changed, 42 insertions(+), 17 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index 8635b5673386..d2dee58e7bf2 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -279,6 +279,7 @@ struct zynqmp_dp_config {
  * @dpsub: Display subsystem
  * @iomem: device I/O memory for register access
  * @reset: reset controller
+ * @lock: Mutex protecting this struct and register access (but not AUX)
  * @irq: irq
  * @bridge: DRM bridge for the DP encoder
  * @next_bridge: The downstream bridge
@@ -299,6 +300,7 @@ struct zynqmp_dp {
 	struct zynqmp_dpsub *dpsub;
 	void __iomem *iomem;
 	struct reset_control *reset;
+	struct mutex lock;
 	int irq;
 
 	struct drm_bridge bridge;
@@ -308,7 +310,7 @@ struct zynqmp_dp {
 	struct drm_dp_aux aux;
 	struct phy *phy[ZYNQMP_DP_MAX_LANES];
 	u8 num_lanes;
-	struct delayed_work hpd_work;
+	struct delayed_work hpd_work, hpd_irq_work;
 	enum drm_connector_status status;
 	bool enabled;
 
@@ -1371,8 +1373,10 @@ zynqmp_dp_bridge_mode_valid(struct drm_bridge *bridge,
 	}
 
 	/* Check with link rate and lane count */
+	mutex_lock(&dp->lock);
 	rate = zynqmp_dp_max_rate(dp->link_config.max_rate,
 				  dp->link_config.max_lanes, dp->config.bpp);
+	mutex_unlock(&dp->lock);
 	if (mode->clock > rate) {
 		dev_dbg(dp->dev, "filtered mode %s for high pixel rate\n",
 			mode->name);
@@ -1399,6 +1403,7 @@ static void zynqmp_dp_bridge_atomic_enable(struct drm_bridge *bridge,
 
 	pm_runtime_get_sync(dp->dev);
 
+	mutex_lock(&dp->lock);
 	zynqmp_dp_disp_enable(dp, old_bridge_state);
 
 	/*
@@ -1459,6 +1464,7 @@ static void zynqmp_dp_bridge_atomic_enable(struct drm_bridge *bridge,
 	zynqmp_dp_write(dp, ZYNQMP_DP_SOFTWARE_RESET,
 			ZYNQMP_DP_SOFTWARE_RESET_ALL);
 	zynqmp_dp_write(dp, ZYNQMP_DP_MAIN_STREAM_ENABLE, 1);
+	mutex_unlock(&dp->lock);
 }
 
 static void zynqmp_dp_bridge_atomic_disable(struct drm_bridge *bridge,
@@ -1466,6 +1472,7 @@ static void zynqmp_dp_bridge_atomic_disable(struct drm_bridge *bridge,
 {
 	struct zynqmp_dp *dp = bridge_to_dp(bridge);
 
+	mutex_lock(&dp->lock);
 	dp->enabled = false;
 	cancel_delayed_work(&dp->hpd_work);
 	zynqmp_dp_write(dp, ZYNQMP_DP_MAIN_STREAM_ENABLE, 0);
@@ -1476,6 +1483,7 @@ static void zynqmp_dp_bridge_atomic_disable(struct drm_bridge *bridge,
 		zynqmp_dp_write(dp, ZYNQMP_DP_TX_AUDIO_CONTROL, 0);
 
 	zynqmp_dp_disp_disable(dp, old_bridge_state);
+	mutex_unlock(&dp->lock);
 
 	pm_runtime_put_sync(dp->dev);
 }
@@ -1518,6 +1526,8 @@ static enum drm_connector_status zynqmp_dp_bridge_detect(struct drm_bridge *brid
 	u32 state, i;
 	int ret;
 
+	mutex_lock(&dp->lock);
+
 	/*
 	 * This is from heuristic. It takes some delay (ex, 100 ~ 500 msec) to
 	 * get the HPD signal with some monitors.
@@ -1545,11 +1555,13 @@ static enum drm_connector_status zynqmp_dp_bridge_detect(struct drm_bridge *brid
 					       dp->num_lanes);
 
 		dp->status = connector_status_connected;
+		mutex_unlock(&dp->lock);
 		return connector_status_connected;
 	}
 
 disconnected:
 	dp->status = connector_status_disconnected;
+	mutex_unlock(&dp->lock);
 	return connector_status_disconnected;
 }
 
@@ -1611,6 +1623,29 @@ static void zynqmp_dp_hpd_work_func(struct work_struct *work)
 	drm_bridge_hpd_notify(&dp->bridge, status);
 }
 
+static void zynqmp_dp_hpd_irq_work_func(struct work_struct *work)
+{
+	struct zynqmp_dp *dp = container_of(work, struct zynqmp_dp,
+					    hpd_irq_work.work);
+	u8 status[DP_LINK_STATUS_SIZE + 2];
+	int err;
+
+	mutex_lock(&dp->lock);
+	err = drm_dp_dpcd_read(&dp->aux, DP_SINK_COUNT, status,
+			       DP_LINK_STATUS_SIZE + 2);
+	if (err < 0) {
+		dev_dbg_ratelimited(dp->dev,
+				    "could not read sink status: %d\n", err);
+	} else {
+		if (status[4] & DP_LINK_STATUS_UPDATED ||
+		    !drm_dp_clock_recovery_ok(&status[2], dp->mode.lane_cnt) ||
+		    !drm_dp_channel_eq_ok(&status[2], dp->mode.lane_cnt)) {
+			zynqmp_dp_train_loop(dp);
+		}
+	}
+	mutex_unlock(&dp->lock);
+}
+
 static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
 {
 	struct zynqmp_dp *dp = (struct zynqmp_dp *)data;
@@ -1635,23 +1670,9 @@ static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
 	if (status & ZYNQMP_DP_INT_HPD_EVENT)
 		schedule_delayed_work(&dp->hpd_work, 0);
 
-	if (status & ZYNQMP_DP_INT_HPD_IRQ) {
-		int ret;
-		u8 status[DP_LINK_STATUS_SIZE + 2];
+	if (status & ZYNQMP_DP_INT_HPD_IRQ)
+		schedule_delayed_work(&dp->hpd_irq_work, 0);
 
-		ret = drm_dp_dpcd_read(&dp->aux, DP_SINK_COUNT, status,
-				       DP_LINK_STATUS_SIZE + 2);
-		if (ret < 0)
-			goto handled;
-
-		if (status[4] & DP_LINK_STATUS_UPDATED ||
-		    !drm_dp_clock_recovery_ok(&status[2], dp->mode.lane_cnt) ||
-		    !drm_dp_channel_eq_ok(&status[2], dp->mode.lane_cnt)) {
-			zynqmp_dp_train_loop(dp);
-		}
-	}
-
-handled:
 	return IRQ_HANDLED;
 }
 
@@ -1674,8 +1695,10 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
 	dp->dev = &pdev->dev;
 	dp->dpsub = dpsub;
 	dp->status = connector_status_disconnected;
+	mutex_init(&dp->lock);
 
 	INIT_DELAYED_WORK(&dp->hpd_work, zynqmp_dp_hpd_work_func);
+	INIT_DELAYED_WORK(&dp->hpd_irq_work, zynqmp_dp_hpd_irq_work_func);
 
 	/* Acquire all resources (IOMEM, IRQ and PHYs). */
 	res = platform_get_resource_byname(pdev, IORESOURCE_MEM, "dp");
@@ -1775,6 +1798,7 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub)
 	zynqmp_dp_write(dp, ZYNQMP_DP_INT_DS, ZYNQMP_DP_INT_ALL);
 	disable_irq(dp->irq);
 
+	cancel_delayed_work_sync(&dp->hpd_irq_work);
 	cancel_delayed_work_sync(&dp->hpd_work);
 
 	zynqmp_dp_write(dp, ZYNQMP_DP_TRANSMITTER_ENABLE, 0);
@@ -1782,4 +1806,5 @@ void zynqmp_dp_remove(struct zynqmp_dpsub *dpsub)
 
 	zynqmp_dp_phy_exit(dp);
 	zynqmp_dp_reset(dp, true);
+	mutex_destroy(&dp->lock);
 }
-- 
2.35.1.1320.gc452695387.dirty