media: mediatek: vcodec: Use spinlock for context list protection lock

Previously a mutex was added to protect the encoder and decoder context
lists from unexpected changes originating from the SCP IP block, causing
the context pointer to go invalid, resulting in a NULL pointer
dereference in the IPI handler.

Turns out on the MT8173, the VPU IPI handler is called from hard IRQ
context. This causes a big warning from the scheduler. This was first
reported downstream on the ChromeOS kernels, but is also reproducible
on mainline using Fluster with the FFmpeg v4l2m2m decoders. Even though
the actual capture format is not supported, the affected code paths
are triggered.

Since this lock just protects the context list and operations on it are
very fast, it should be OK to switch to a spinlock.

Fixes: 6467cda18c9f ("media: mediatek: vcodec: adding lock to protect decoder context list")
Fixes: afaaf3a0f647 ("media: mediatek: vcodec: adding lock to protect encoder context list")
Cc: Yunfei Dong <yunfei.dong@mediatek.com>
Cc: stable@vger.kernel.org
Signed-off-by: Chen-Yu Tsai <wenst@chromium.org>
Reviewed-by: Fei Shao <fshao@chromium.org>
Reviewed-by: Tomasz Figa <tfiga@chromium.org>
Signed-off-by: Nicolas Dufresne <nicolas.dufresne@collabora.com>
Signed-off-by: Hans Verkuil <hverkuil+cisco@kernel.org>

3 files changed, 11 insertions, 8 deletions

diff --git a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
index fb1c3bdc2dae..82b8ff38e8f1 100644
--- a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
+++ b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c
@@ -117,6 +117,7 @@ static int fops_vcodec_open(struct file *file)
 	struct mtk_vcodec_enc_ctx *ctx = NULL;
 	int ret = 0;
 	struct vb2_queue *src_vq;
+	unsigned long flags;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
@@ -176,9 +177,9 @@ static int fops_vcodec_open(struct file *file)
 	mtk_v4l2_venc_dbg(2, ctx, "Create instance [%d]@%p m2m_ctx=%p ",
 			  ctx->id, ctx, ctx->m2m_ctx);
 
-	mutex_lock(&dev->dev_ctx_lock);
+	spin_lock_irqsave(&dev->dev_ctx_lock, flags);
 	list_add(&ctx->list, &dev->ctx_list);
-	mutex_unlock(&dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&dev->dev_ctx_lock, flags);
 
 	mutex_unlock(&dev->dev_mutex);
 	mtk_v4l2_venc_dbg(0, ctx, "%s encoder [%d]", dev_name(&dev->plat_dev->dev),
@@ -203,6 +204,7 @@ static int fops_vcodec_release(struct file *file)
 {
 	struct mtk_vcodec_enc_dev *dev = video_drvdata(file);
 	struct mtk_vcodec_enc_ctx *ctx = file_to_enc_ctx(file);
+	unsigned long flags;
 
 	mtk_v4l2_venc_dbg(1, ctx, "[%d] encoder", ctx->id);
 	mutex_lock(&dev->dev_mutex);
@@ -213,9 +215,9 @@ static int fops_vcodec_release(struct file *file)
 	v4l2_fh_exit(&ctx->fh);
 	v4l2_ctrl_handler_free(&ctx->ctrl_hdl);
 
-	mutex_lock(&dev->dev_ctx_lock);
+	spin_lock_irqsave(&dev->dev_ctx_lock, flags);
 	list_del_init(&ctx->list);
-	mutex_unlock(&dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&dev->dev_ctx_lock, flags);
 	kfree(ctx);
 	mutex_unlock(&dev->dev_mutex);
 	return 0;
@@ -297,7 +299,7 @@ static int mtk_vcodec_probe(struct platform_device *pdev)
 
 	mutex_init(&dev->enc_mutex);
 	mutex_init(&dev->dev_mutex);
-	mutex_init(&dev->dev_ctx_lock);
+	spin_lock_init(&dev->dev_ctx_lock);
 	spin_lock_init(&dev->irqlock);
 
 	snprintf(dev->v4l2_dev.name, sizeof(dev->v4l2_dev.name), "%s",
diff --git a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
index 5b304a551236..0cddfa13594f 100644
--- a/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
+++ b/drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h
@@ -206,7 +206,7 @@ struct mtk_vcodec_enc_dev {
 	/* encoder hardware mutex lock */
 	struct mutex enc_mutex;
 	struct mutex dev_mutex;
-	struct mutex dev_ctx_lock;
+	spinlock_t dev_ctx_lock;
 	struct workqueue_struct *encode_workqueue;
 
 	int enc_irq;
diff --git a/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c b/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
index 51bb7ee141b9..3c229b1f6b21 100644
--- a/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
+++ b/drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c
@@ -45,16 +45,17 @@ static void handle_enc_encode_msg(struct venc_vpu_inst *vpu, const void *data)
 static bool vpu_enc_check_ap_inst(struct mtk_vcodec_enc_dev *enc_dev, struct venc_vpu_inst *vpu)
 {
 	struct mtk_vcodec_enc_ctx *ctx;
+	unsigned long flags;
 	int ret = false;
 
-	mutex_lock(&enc_dev->dev_ctx_lock);
+	spin_lock_irqsave(&enc_dev->dev_ctx_lock, flags);
 	list_for_each_entry(ctx, &enc_dev->ctx_list, list) {
 		if (!IS_ERR_OR_NULL(ctx) && ctx->vpu_inst == vpu) {
 			ret = true;
 			break;
 		}
 	}
-	mutex_unlock(&enc_dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&enc_dev->dev_ctx_lock, flags);
 
 	return ret;
 }