linux-kernel - [PATCH v2 5/8] drm: zynqmp_dp: Don't retrain the link in our IRQ

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Message-Id: <20240319225122.3048400-6-sean.anderson@linux.dev>
Date: Tue, 19 Mar 2024 18:51:18 -0400
From: Sean Anderson <sean.anderson@...ux.dev>
To: Laurent Pinchart <laurent.pinchart@...asonboard.com>,
	Maarten Lankhorst <maarten.lankhorst@...ux.intel.com>,
	Maxime Ripard <mripard@...nel.org>,
	Thomas Zimmermann <tzimmermann@...e.de>,
	dri-devel@...ts.freedesktop.org
Cc: Michal Simek <michal.simek@....com>,
	David Airlie <airlied@...il.com>,
	linux-kernel@...r.kernel.org,
	Daniel Vetter <daniel@...ll.ch>,
	linux-arm-kernel@...ts.infradead.org,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH v2 5/8] drm: zynqmp_dp: Don't retrain the link in our IRQ

Retraining the link can take a while, and might involve waiting for
DPCD reads/writes to complete. This is inappropriate for an IRQ handler.
Just schedule this work for later completion. This is racy, but will be
fixed in the next commit.

Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
---
Actually, on second look this IRQ is threaded. So why do we have a
workqueue for HPD events? Maybe we should make it unthreaded?

Changes in v2:
- Document hpd_irq_work
- Split this off from the lcoking changes

 drivers/gpu/drm/xlnx/zynqmp_dp.c | 43 ++++++++++++++++++++------------
 1 file changed, 27 insertions(+), 16 deletions(-)

diff --git a/drivers/gpu/drm/xlnx/zynqmp_dp.c b/drivers/gpu/drm/xlnx/zynqmp_dp.c
index f1834c8e3c02..f3fcdbf662fa 100644
--- a/drivers/gpu/drm/xlnx/zynqmp_dp.c
+++ b/drivers/gpu/drm/xlnx/zynqmp_dp.c
@@ -287,6 +287,7 @@ struct zynqmp_dp_config {
  * @phy: PHY handles for DP lanes
  * @num_lanes: number of enabled phy lanes
  * @hpd_work: hot plug detection worker
+ * @hpd_irq_work: hot plug detection IRQ worker
  * @status: connection status
  * @enabled: flag to indicate if the device is enabled
  * @dpcd: DP configuration data from currently connected sink device
@@ -298,6 +299,7 @@ struct zynqmp_dp {
 	struct drm_dp_aux aux;
 	struct drm_bridge bridge;
 	struct delayed_work hpd_work;
+	struct delayed_work hpd_irq_work;
 
 	struct drm_bridge *next_bridge;
 	struct device *dev;
@@ -1611,6 +1613,27 @@ 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;
+
+	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);
+		}
+	}
+}
+
 static irqreturn_t zynqmp_dp_irq_handler(int irq, void *data)
 {
 	struct zynqmp_dp *dp = (struct zynqmp_dp *)data;
@@ -1635,23 +1658,9 @@ 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;
 }
 
@@ -1676,6 +1685,7 @@ int zynqmp_dp_probe(struct zynqmp_dpsub *dpsub)
 	dp->status = connector_status_disconnected;
 
 	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 +1785,7 @@ 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);
-- 
2.35.1.1320.gc452695387.dirty