media: cedrus: Remove global IRQ spin lock from the driver

We initially introduced a spin lock to ensure that the VPU registers
are not accessed concurrently between our setup function and IRQ
handler. The V4L2 M2M API ensures that only one decoding job runs at a
time, so the interrupt signaling the end of decoding will not occur
while the next picture is being configured.

Spurious interrupts are taken care of in the handler, by checking that
we have a valid M2M context and a decoding status available before
marking the buffers as done.

In addition, holding a spin lock could be problematic if non-atomic
operations are required in the setup process for future codec support.

As a result, remove the global IRQ spin lock.

Signed-off-by: Paul Kocialkowski <paul.kocialkowski@bootlin.com>
Acked-by: Maxime Ripard <maxime.ripard@bootlin.com>
Signed-off-by: Hans Verkuil <hverkuil-cisco@xs4all.nl>
Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>

drivers/staging/media/sunxi/cedrus/cedrus.c

@@ -279,7 +279,6 @@ static int cedrus_probe(struct platform_device *pdev)
 	dev->dec_ops[CEDRUS_CODEC_MPEG2] = &cedrus_dec_ops_mpeg2;
 
 	mutex_init(&dev->dev_mutex);
-	spin_lock_init(&dev->irq_lock);
 
 	ret = v4l2_device_register(&pdev->dev, &dev->v4l2_dev);
 	if (ret) {

drivers/staging/media/sunxi/cedrus/cedrus.h

@@ -105,8 +105,6 @@ struct cedrus_dev {
 
 	/* Device file mutex */
 	struct mutex		dev_mutex;
-	/* Interrupt spinlock */
-	spinlock_t		irq_lock;
 
 	void __iomem		*base;
 

drivers/staging/media/sunxi/cedrus/cedrus_dec.c

@@ -28,7 +28,6 @@ void cedrus_device_run(void *priv)
 	struct cedrus_dev *dev = ctx->dev;
 	struct cedrus_run run = { 0 };
 	struct media_request *src_req;
-	unsigned long flags;
 
 	run.src = v4l2_m2m_next_src_buf(ctx->fh.m2m_ctx);
 	run.dst = v4l2_m2m_next_dst_buf(ctx->fh.m2m_ctx);
@@ -39,8 +38,6 @@ void cedrus_device_run(void *priv)
 	if (src_req)
 		v4l2_ctrl_request_setup(src_req, &ctx->hdl);
 
-	spin_lock_irqsave(&ctx->dev->irq_lock, flags);
-
 	switch (ctx->src_fmt.pixelformat) {
 	case V4L2_PIX_FMT_MPEG2_SLICE:
 		run.mpeg2.slice_params = cedrus_find_control_data(ctx,
@@ -55,16 +52,10 @@ void cedrus_device_run(void *priv)
 
 	dev->dec_ops[ctx->current_codec]->setup(ctx, &run);
 
-	spin_unlock_irqrestore(&ctx->dev->irq_lock, flags);
-
 	/* Complete request(s) controls if needed. */
 
 	if (src_req)
 		v4l2_ctrl_request_complete(src_req, &ctx->hdl);
 
-	spin_lock_irqsave(&ctx->dev->irq_lock, flags);
-
 	dev->dec_ops[ctx->current_codec]->trigger(ctx);
-
-	spin_unlock_irqrestore(&ctx->dev->irq_lock, flags);
 }

drivers/staging/media/sunxi/cedrus/cedrus_hw.c

@@ -105,24 +105,17 @@ static irqreturn_t cedrus_irq(int irq, void *data)
 	struct vb2_v4l2_buffer *src_buf, *dst_buf;
 	enum vb2_buffer_state state;
 	enum cedrus_irq_status status;
-	unsigned long flags;
-
-	spin_lock_irqsave(&dev->irq_lock, flags);
 
 	ctx = v4l2_m2m_get_curr_priv(dev->m2m_dev);
 	if (!ctx) {
 		v4l2_err(&dev->v4l2_dev,
 			 "Instance released before the end of transaction\n");
-		spin_unlock_irqrestore(&dev->irq_lock, flags);
-
 		return IRQ_NONE;
 	}
 
 	status = dev->dec_ops[ctx->current_codec]->irq_status(ctx);
-	if (status == CEDRUS_IRQ_NONE) {
-		spin_unlock_irqrestore(&dev->irq_lock, flags);
+	if (status == CEDRUS_IRQ_NONE)
 		return IRQ_NONE;
-	}
 
 	dev->dec_ops[ctx->current_codec]->irq_disable(ctx);
 	dev->dec_ops[ctx->current_codec]->irq_clear(ctx);
@@ -133,8 +126,6 @@ static irqreturn_t cedrus_irq(int irq, void *data)
 	if (!src_buf || !dst_buf) {
 		v4l2_err(&dev->v4l2_dev,
 			 "Missing source and/or destination buffers\n");
-		spin_unlock_irqrestore(&dev->irq_lock, flags);
-
 		return IRQ_HANDLED;
 	}
 
@@ -146,8 +137,6 @@ static irqreturn_t cedrus_irq(int irq, void *data)
 	v4l2_m2m_buf_done(src_buf, state);
 	v4l2_m2m_buf_done(dst_buf, state);
 
-	spin_unlock_irqrestore(&dev->irq_lock, flags);
-
 	v4l2_m2m_job_finish(ctx->dev->m2m_dev, ctx->fh.m2m_ctx);
 
 	return IRQ_HANDLED;

drivers/staging/media/sunxi/cedrus/cedrus_video.c

@@ -380,18 +380,13 @@ static void cedrus_queue_cleanup(struct vb2_queue *vq, u32 state)
 {
 	struct cedrus_ctx *ctx = vb2_get_drv_priv(vq);
 	struct vb2_v4l2_buffer *vbuf;
-	unsigned long flags;
 
 	for (;;) {
-		spin_lock_irqsave(&ctx->dev->irq_lock, flags);
-
 		if (V4L2_TYPE_IS_OUTPUT(vq->type))
 			vbuf = v4l2_m2m_src_buf_remove(ctx->fh.m2m_ctx);
 		else
 			vbuf = v4l2_m2m_dst_buf_remove(ctx->fh.m2m_ctx);
 
-		spin_unlock_irqrestore(&ctx->dev->irq_lock, flags);
-
 		if (!vbuf)
 			return;