diff mbox series

[v3,2/2] drm/mediatek: change config_lock from spin_lock to spin_lock_irqsave

Message ID 20240827-drm-fixup-0819-v3-2-4761005211ec@mediatek.com (mailing list archive)
State New
Headers show
Series Fix missing configuration flags in mtk_crtc_ddp_config | expand

Commit Message

Jason-JH.Lin via B4 Relay Aug. 27, 2024, 2:55 p.m. UTC 
From: "Jason-JH.Lin" <jason-jh.lin@mediatek.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@mediatek.com>
---
 drivers/gpu/drm/mediatek/mtk_crtc.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

Comments

Fei Shao Aug. 28, 2024, 9:41 a.m. UTC | #1 
Hi Jason,

On Tue, Aug 27, 2024 at 10:58 PM Jason-JH.Lin via B4 Relay
<devnull+jason-jh.lin.mediatek.com@kernel.org> wrote:
>
> From: "Jason-JH.Lin" <jason-jh.lin@mediatek.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")

The appropriate fix tag should be:
Fixes: 1bbb2be61bbb ("drm/mediatek: Fix missing configuration flags in
mtk_crtc_ddp_config()")

I don't know if it's worth resending though.
I guess it's up to CK if he's willing to replace it when picking up the patch.

But the change itself is valid, so after fixing that:
Reviewed-by: Fei Shao <fshao@chromium.org>

Regards,
Fei

> Signed-off-by: Jason-JH.Lin <jason-jh.lin@mediatek.com>
diff mbox series

Patch

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);
 }