[media] s5p-fimc: fimc-lite: Prevent deadlock at STREAMON/OFF ioctls

This patch fixes regression introduced in commit 6319d6a002beb26631
'[media] fimc-lite: Add ISP FIFO output support'.
In case of a configuration where video is captured at the video node
exposed by the FIMC-LITE driver there is a following video pipeline:
sensor -> MIPI-CSIS.n -> FIMC-LITE.n subdev -> FIMC-LITE.n video node
In this situation s_stream() handler of the FIMC-LITE.n is called
back from within VIDIOC_STREAMON/OFF ioctl of the FIMC-LITE.n video
node, through vb2_stream_on/off(), start/stop_streaming and
fimc_pipeline_call(set_stream). The fimc->lock mutex is already held
then, before invoking vidioc_streamon/off. So it must not be taken
again in the s_stream() callback in this case, to avoid a deadlock.
This patch makes fimc->out_path atomic_t so the mutex don't need
to be taken in the FIMC-LITE subdev s_stream() callback in the DMA
output case.

Signed-off-by: Sylwester Nawrocki <s.nawrocki@samsung.com>
Signed-off-by: Kyugmin Park <kyungmin.park@samsung.com>
Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>

3 files changed, 21 insertions, 18 deletions

diff --git a/drivers/media/platform/s5p-fimc/fimc-lite-reg.c b/drivers/media/platform/s5p-fimc/fimc-lite-reg.c
index ad63ebf082c5..962652da3b43 100644
--- a/drivers/media/platform/s5p-fimc/fimc-lite-reg.c
+++ b/drivers/media/platform/s5p-fimc/fimc-lite-reg.c
@@ -65,7 +65,7 @@ void flite_hw_set_interrupt_mask(struct fimc_lite *dev)
         u32 cfg, intsrc;
 
         /* Select interrupts to be enabled for each output mode */
-        if (dev->out_path == FIMC_IO_DMA) {
+        if (atomic_read(&dev->out_path) == FIMC_IO_DMA) {
                 intsrc = FLITE_REG_CIGCTRL_IRQ_OVFEN |
                          FLITE_REG_CIGCTRL_IRQ_LASTEN |
                          FLITE_REG_CIGCTRL_IRQ_STARTEN;
diff --git a/drivers/media/platform/s5p-fimc/fimc-lite.c b/drivers/media/platform/s5p-fimc/fimc-lite.c
index fe6cd0c3bdd3..ef3989fe63e5 100644
--- a/drivers/media/platform/s5p-fimc/fimc-lite.c
+++ b/drivers/media/platform/s5p-fimc/fimc-lite.c
@@ -260,7 +260,7 @@ static irqreturn_t flite_irq_handler(int irq, void *priv)
                 wake_up(&fimc->irq_queue);
         }
 
-        if (fimc->out_path != FIMC_IO_DMA)
+        if (atomic_read(&fimc->out_path) != FIMC_IO_DMA)
                 goto done;
 
         if ((intsrc & FLITE_REG_CISTATUS_IRQ_SRC_FRMSTART) &&
@@ -465,7 +465,7 @@ static int fimc_lite_open(struct file *file)
         mutex_lock(&me->parent->graph_mutex);
 
         mutex_lock(&fimc->lock);
-        if (fimc->out_path != FIMC_IO_DMA) {
+        if (atomic_read(&fimc->out_path) != FIMC_IO_DMA) {
                 ret = -EBUSY;
                 goto done;
         }
@@ -479,7 +479,8 @@ static int fimc_lite_open(struct file *file)
         if (ret < 0)
                 goto done;
 
-        if (++fimc->ref_count == 1 && fimc->out_path == FIMC_IO_DMA) {
+        if (++fimc->ref_count == 1 &&
+            atomic_read(&fimc->out_path) == FIMC_IO_DMA) {
                 ret = fimc_pipeline_call(fimc, open, &fimc->pipeline,
                                          &fimc->vfd.entity, true);
                 if (ret < 0) {
@@ -504,7 +505,8 @@ static int fimc_lite_close(struct file *file)
 
         mutex_lock(&fimc->lock);
 
-        if (--fimc->ref_count == 0 && fimc->out_path == FIMC_IO_DMA) {
+        if (--fimc->ref_count == 0 &&
+            atomic_read(&fimc->out_path) == FIMC_IO_DMA) {
                 clear_bit(ST_FLITE_IN_USE, &fimc->state);
                 fimc_lite_stop_capture(fimc, false);
                 fimc_pipeline_call(fimc, close, &fimc->pipeline);
@@ -1034,18 +1036,18 @@ static int fimc_lite_link_setup(struct media_entity *entity,
 
         case FLITE_SD_PAD_SOURCE_DMA:
                 if (!(flags & MEDIA_LNK_FL_ENABLED))
-                        fimc->out_path = FIMC_IO_NONE;
+                        atomic_set(&fimc->out_path, FIMC_IO_NONE);
                 else if (remote_ent_type == MEDIA_ENT_T_DEVNODE)
-                        fimc->out_path = FIMC_IO_DMA;
+                        atomic_set(&fimc->out_path, FIMC_IO_DMA);
                 else
                         ret = -EINVAL;
                 break;
 
         case FLITE_SD_PAD_SOURCE_ISP:
                 if (!(flags & MEDIA_LNK_FL_ENABLED))
-                        fimc->out_path = FIMC_IO_NONE;
+                        atomic_set(&fimc->out_path, FIMC_IO_NONE);
                 else if (remote_ent_type == MEDIA_ENT_T_V4L2_SUBDEV)
-                        fimc->out_path = FIMC_IO_ISP;
+                        atomic_set(&fimc->out_path, FIMC_IO_ISP);
                 else
                         ret = -EINVAL;
                 break;
@@ -1054,6 +1056,7 @@ static int fimc_lite_link_setup(struct media_entity *entity,
                 v4l2_err(sd, "Invalid pad index\n");
                 ret = -EINVAL;
         }
+        mb();
 
         mutex_unlock(&fimc->lock);
         return ret;
@@ -1123,8 +1126,10 @@ static int fimc_lite_subdev_set_fmt(struct v4l2_subdev *sd,
         mf->colorspace = V4L2_COLORSPACE_JPEG;
         mutex_lock(&fimc->lock);
 
-        if ((fimc->out_path == FIMC_IO_ISP && sd->entity.stream_count > 0) ||
-            (fimc->out_path == FIMC_IO_DMA && vb2_is_busy(&fimc->vb_queue))) {
+        if ((atomic_read(&fimc->out_path) == FIMC_IO_ISP &&
+            sd->entity.stream_count > 0) ||
+            (atomic_read(&fimc->out_path) == FIMC_IO_DMA &&
+            vb2_is_busy(&fimc->vb_queue))) {
                 mutex_unlock(&fimc->lock);
                 return -EBUSY;
         }
@@ -1247,12 +1252,10 @@ static int fimc_lite_subdev_s_stream(struct v4l2_subdev *sd, int on)
          */
         fimc->sensor = __find_remote_sensor(&sd->entity);
 
-        mutex_lock(&fimc->lock);
-        if (fimc->out_path != FIMC_IO_ISP) {
-                mutex_unlock(&fimc->lock);
+        if (atomic_read(&fimc->out_path) != FIMC_IO_ISP)
                 return -ENOIOCTLCMD;
-        }
 
+        mutex_lock(&fimc->lock);
         if (on) {
                 flite_hw_reset(fimc);
                 ret = fimc_lite_hw_init(fimc, true);
@@ -1298,7 +1301,7 @@ static int fimc_lite_subdev_registered(struct v4l2_subdev *sd)
         memset(vfd, 0, sizeof(*vfd));
 
         fimc->fmt = &fimc_lite_formats[0];
-        fimc->out_path = FIMC_IO_DMA;
+        atomic_set(&fimc->out_path, FIMC_IO_DMA);
 
         snprintf(vfd->name, sizeof(vfd->name), "fimc-lite.%d.capture",
                  fimc->index);
@@ -1589,7 +1592,7 @@ static int fimc_lite_resume(struct device *dev)
         INIT_LIST_HEAD(&fimc->active_buf_q);
         fimc_pipeline_call(fimc, open, &fimc->pipeline,
                            &fimc->vfd.entity, false);
-        fimc_lite_hw_init(fimc, fimc->out_path == FIMC_IO_ISP);
+        fimc_lite_hw_init(fimc, atomic_read(&fimc->out_path) == FIMC_IO_ISP);
         clear_bit(ST_FLITE_SUSPENDED, &fimc->state);
 
         for (i = 0; i < fimc->reqbufs_count; i++) {
diff --git a/drivers/media/platform/s5p-fimc/fimc-lite.h b/drivers/media/platform/s5p-fimc/fimc-lite.h
index 4576922952f3..7085761f8c4b 100644
--- a/drivers/media/platform/s5p-fimc/fimc-lite.h
+++ b/drivers/media/platform/s5p-fimc/fimc-lite.h
@@ -159,7 +159,7 @@ struct fimc_lite {
         unsigned long           payload[FLITE_MAX_PLANES];
         struct flite_frame      inp_frame;
         struct flite_frame      out_frame;
-        enum fimc_datapath      out_path;
+        atomic_t                out_path;
         unsigned int            source_subdev_grp_id;
 
         unsigned long           state;