disp: msm: sde: add cb func check before enabling irq

Acquiring mutex lock after enabling irq might lead to
deadlock if irq is dispatched immediately in some cases.
This change moves callback func check for irq prior to
enabling the irq line.

Change-Id: Ie1622e1ade268e41e97bf6d7683fa0bd972bcb7c
Signed-off-by: Yashwanth <[email protected]>

msm/sde/sde_core_irq.c

@@ -1,6 +1,6 @@
 // SPDX-License-Identifier: GPL-2.0-only
 /*
- * Copyright (c) 2015-2019, The Linux Foundation. All rights reserved.
+ * Copyright (c) 2015-2020, The Linux Foundation. All rights reserved.
  */
 
 #define pr_fmt(fmt)	"[drm:%s:%d] " fmt, __func__, __LINE__
@@ -115,24 +115,26 @@ static int _sde_core_irq_enable(struct sde_kms *sde_kms, int irq_idx)
 
 	SDE_EVT32(irq_idx,
 			atomic_read(&sde_kms->irq_obj.enable_counts[irq_idx]));
-	spin_lock_irqsave(&sde_kms->hw_intr->irq_lock, irq_flags);
-	if (atomic_inc_return(&sde_kms->irq_obj.enable_counts[irq_idx]) == 1)
+
+	if (atomic_inc_return(&sde_kms->irq_obj.enable_counts[irq_idx]) == 1) {
+		spin_lock_irqsave(&sde_kms->irq_obj.cb_lock, irq_flags);
+		/* empty callback list but interrupt is being enabled */
+		if (list_empty(&sde_kms->irq_obj.irq_cb_tbl[irq_idx]))
+			SDE_ERROR("enabling irq_idx=%d with no callback\n",
+					irq_idx);
+		spin_unlock_irqrestore(&sde_kms->irq_obj.cb_lock, irq_flags);
+
+		spin_lock_irqsave(&sde_kms->hw_intr->irq_lock, irq_flags);
 		ret = sde_kms->hw_intr->ops.enable_irq_nolock(
 				sde_kms->hw_intr, irq_idx);
-	spin_unlock_irqrestore(&sde_kms->hw_intr->irq_lock, irq_flags);
+		spin_unlock_irqrestore(&sde_kms->hw_intr->irq_lock, irq_flags);
+	}
+
 	if (ret)
 		SDE_ERROR("Fail to enable IRQ for irq_idx:%d\n", irq_idx);
 
 	SDE_DEBUG("irq_idx=%d ret=%d\n", irq_idx, ret);
 
-	if (atomic_read(&sde_kms->irq_obj.enable_counts[irq_idx]) == 1) {
-		spin_lock_irqsave(&sde_kms->irq_obj.cb_lock, irq_flags);
-		/* empty callback list but interrupt is enabled */
-		if (list_empty(&sde_kms->irq_obj.irq_cb_tbl[irq_idx]))
-			SDE_ERROR("irq_idx=%d enabled with no callback\n",
-					irq_idx);
-		spin_unlock_irqrestore(&sde_kms->irq_obj.cb_lock, irq_flags);
-	}
 	return ret;
 }