linux-kernel - [PATCH v3 2/2] drm/mediatek: change config_lock from spin_lock to spin_lock

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Message-Id: <20240827-drm-fixup-0819-v3-2-4761005211ec@mediatek.com>
Date: Tue, 27 Aug 2024 22:55:20 +0800
From: "Jason-JH.Lin via B4 Relay" <devnull+jason-jh.lin.mediatek.com@...nel.org>
To: Chun-Kuang Hu <chunkuang.hu@...nel.org>, 
 AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
Cc: Philipp Zabel <p.zabel@...gutronix.de>, 
 David Airlie <airlied@...il.com>, Daniel Vetter <daniel@...ll.ch>, 
 Singo Chang <singo.chang@...iatek.com>, Nancy Lin <nancy.lin@...iatek.com>, 
 "Jason-JH.Lin" <jason-jh.lin@...iatek.com>, 
 Project_Global_Chrome_Upstream_Group@...iatek.com, 
 dri-devel@...ts.freedesktop.org, linux-mediatek@...ts.infradead.org, 
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: [PATCH v3 2/2] drm/mediatek: change config_lock from spin_lock to
 spin_lock_irqsave

From: "Jason-JH.Lin" <jason-jh.lin@...iatek.com>

Operations within spin_locks are limited to fast memory access and
confirmation of minimum lock duration.

Although using spin_lock with config_lock seems to ensure shorter hold
times, it is safer to use spin_lock_irqsave due to potential deadlocks
and nested interrupt scenarios in interrupt contexts.

So change config_lock from spin_lock to spin_lock_irqsave.

Fixes: 7f82d9c43879 ("drm/mediatek: Clear pending flag when cmdq packet is done")
Signed-off-by: Jason-JH.Lin <jason-jh.lin@...iatek.com>
---
 drivers/gpu/drm/mediatek/mtk_crtc.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/gpu/drm/mediatek/mtk_crtc.c b/drivers/gpu/drm/mediatek/mtk_crtc.c
index b752c0b46383..d7f0926f896d 100644
--- a/drivers/gpu/drm/mediatek/mtk_crtc.c
+++ b/drivers/gpu/drm/mediatek/mtk_crtc.c
@@ -108,14 +108,16 @@ static void mtk_crtc_finish_page_flip(struct mtk_crtc *mtk_crtc)
 
 static void mtk_drm_finish_page_flip(struct mtk_crtc *mtk_crtc)
 {
+	unsigned long flags;
+
 	drm_crtc_handle_vblank(&mtk_crtc->base);
 
-	spin_lock(&mtk_crtc->config_lock);
+	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
 	if (!mtk_crtc->config_updating && mtk_crtc->pending_needs_vblank) {
 		mtk_crtc_finish_page_flip(mtk_crtc);
 		mtk_crtc->pending_needs_vblank = false;
 	}
-	spin_unlock(&mtk_crtc->config_lock);
+	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
 }
 
 #if IS_REACHABLE(CONFIG_MTK_CMDQ)
@@ -313,16 +315,16 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
 	struct mtk_crtc *mtk_crtc = container_of(cmdq_cl, struct mtk_crtc, cmdq_client);
 	struct mtk_crtc_state *state;
 	unsigned int i;
+	unsigned long flags;
 
 	if (data->sta < 0)
 		return;
 
 	state = to_mtk_crtc_state(mtk_crtc->base.state);
 
-	spin_lock(&mtk_crtc->config_lock);
-
+	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
 	if (mtk_crtc->config_updating) {
-		spin_unlock(&mtk_crtc->config_lock);
+		spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
 		goto ddp_cmdq_cb_out;
 	}
 
@@ -352,7 +354,7 @@ static void ddp_cmdq_cb(struct mbox_client *cl, void *mssg)
 		mtk_crtc->pending_async_planes = false;
 	}
 
-	spin_unlock(&mtk_crtc->config_lock);
+	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
 
 ddp_cmdq_cb_out:
 
@@ -585,12 +587,13 @@ static void mtk_crtc_update_config(struct mtk_crtc *mtk_crtc, bool needs_vblank)
 	struct mtk_drm_private *priv = crtc->dev->dev_private;
 	unsigned int pending_planes = 0, pending_async_planes = 0;
 	int i;
+	unsigned long flags;
 
 	mutex_lock(&mtk_crtc->hw_lock);
 
-	spin_lock(&mtk_crtc->config_lock);
+	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
 	mtk_crtc->config_updating = true;
-	spin_unlock(&mtk_crtc->config_lock);
+	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
 
 	if (needs_vblank)
 		mtk_crtc->pending_needs_vblank = true;
@@ -645,9 +648,9 @@ static void mtk_crtc_update_config(struct mtk_crtc *mtk_crtc, bool needs_vblank)
 		mbox_client_txdone(mtk_crtc->cmdq_client.chan, 0);
 	}
 #endif
-	spin_lock(&mtk_crtc->config_lock);
+	spin_lock_irqsave(&mtk_crtc->config_lock, flags);
 	mtk_crtc->config_updating = false;
-	spin_unlock(&mtk_crtc->config_lock);
+	spin_unlock_irqrestore(&mtk_crtc->config_lock, flags);
 
 	mutex_unlock(&mtk_crtc->hw_lock);
 }

-- 
2.43.0