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

From: Jason-JH.Lin via B4 Relay
Date: Tue Aug 27 2024 - 10:57:48 EST


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

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@xxxxxxxxxxxx>
---
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