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 <[e-mail]>
Cc: [e-mail]
Signed-off-by: Chen-Yu Tsai <[e-mail]>
Reviewed-by: Fei Shao <[e-mail]>
Reviewed-by: Tomasz Figa <[e-mail]>
Signed-off-by: Nicolas Dufresne <[e-mail]>
Signed-off-by: Hans Verkuil <[e-mail]>

drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c

···
 {
 	struct mtk_vcodec_dec_dev *dev = priv;
 	struct mtk_vcodec_dec_ctx *ctx;
+	unsigned long flags;
 
 	dev_err(&dev->plat_dev->dev, "Watchdog timeout!!");
 
-	mutex_lock(&dev->dev_ctx_lock);
+	spin_lock_irqsave(&dev->dev_ctx_lock, flags);
 	list_for_each_entry(ctx, &dev->ctx_list, list) {
 		ctx->state = MTK_STATE_ABORT;
 		mtk_v4l2_vdec_dbg(0, ctx, "[%d] Change to state MTK_STATE_ABORT", ctx->id);
 	}
-	mutex_unlock(&dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&dev->dev_ctx_lock, flags);
 }
 
 static void mtk_vcodec_vpu_reset_enc_handler(void *priv)
 {
 	struct mtk_vcodec_enc_dev *dev = priv;
 	struct mtk_vcodec_enc_ctx *ctx;
+	unsigned long flags;
 
 	dev_err(&dev->plat_dev->dev, "Watchdog timeout!!");
 
-	mutex_lock(&dev->dev_ctx_lock);
+	spin_lock_irqsave(&dev->dev_ctx_lock, flags);
 	list_for_each_entry(ctx, &dev->ctx_list, list) {
 		ctx->state = MTK_STATE_ABORT;
 		mtk_v4l2_vdec_dbg(0, ctx, "[%d] Change to state MTK_STATE_ABORT", ctx->id);
 	}
-	mutex_unlock(&dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&dev->dev_ctx_lock, flags);
 }
 
 static const struct mtk_vcodec_fw_ops mtk_vcodec_vpu_msg = {

drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.c

···
 	struct mtk_vcodec_dec_ctx *ctx = NULL;
 	int ret = 0, i, hw_count;
 	struct vb2_queue *src_vq;
+	unsigned long flags;
 
 	ctx = kzalloc(sizeof(*ctx), GFP_KERNEL);
 	if (!ctx)
···
 
 	ctx->dev->vdec_pdata->init_vdec_params(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);
 	mtk_vcodec_dbgfs_create(ctx);
 
 	mutex_unlock(&dev->dev_mutex);
···
 {
 	struct mtk_vcodec_dec_dev *dev = video_drvdata(file);
 	struct mtk_vcodec_dec_ctx *ctx = file_to_dec_ctx(file);
+	unsigned long flags;
 
 	mtk_v4l2_vdec_dbg(0, ctx, "[%d] decoder", ctx->id);
 	mutex_lock(&dev->dev_mutex);
···
 	v4l2_ctrl_handler_free(&ctx->ctrl_hdl);
 
 	mtk_vcodec_dbgfs_remove(dev, ctx->id);
-	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;
···
 	for (i = 0; i < MTK_VDEC_HW_MAX; i++)
 		mutex_init(&dev->dec_mutex[i]);
 	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",

drivers/media/platform/mediatek/vcodec/decoder/mtk_vcodec_dec_drv.h

···
 	/* decoder hardware mutex lock */
 	struct mutex dec_mutex[MTK_VDEC_HW_MAX];
 	struct mutex dev_mutex;
-	struct mutex dev_ctx_lock;
+	spinlock_t dev_ctx_lock;
 	struct workqueue_struct *decode_workqueue;
 
 	spinlock_t irqlock;

drivers/media/platform/mediatek/vcodec/decoder/vdec_vpu_if.c

···
 static bool vpu_dec_check_ap_inst(struct mtk_vcodec_dec_dev *dec_dev, struct vdec_vpu_inst *vpu)
 {
 	struct mtk_vcodec_dec_ctx *ctx;
+	unsigned long flags;
 	int ret = false;
 
-	mutex_lock(&dec_dev->dev_ctx_lock);
+	spin_lock_irqsave(&dec_dev->dev_ctx_lock, flags);
 	list_for_each_entry(ctx, &dec_dev->ctx_list, list) {
 		if (!IS_ERR_OR_NULL(ctx) && ctx->vpu_inst == vpu) {
 			ret = true;
 			break;
 		}
 	}
-	mutex_unlock(&dec_dev->dev_ctx_lock);
+	spin_unlock_irqrestore(&dec_dev->dev_ctx_lock, flags);
 
 	return ret;
 }

drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.c

···
 	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)
···
 	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),
···
 {
 	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);
···
 	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;
···
 
 	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",

drivers/media/platform/mediatek/vcodec/encoder/mtk_vcodec_enc_drv.h

···
 	/* 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;

drivers/media/platform/mediatek/vcodec/encoder/venc_vpu_if.c

···
 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;
 }