diff options
Diffstat (limited to 'drivers/media/pci/saa7134/saa7134-video.c')
| -rw-r--r-- | drivers/media/pci/saa7134/saa7134-video.c | 13 |
1 files changed, 13 insertions, 0 deletions
diff --git a/drivers/media/pci/saa7134/saa7134-video.c b/drivers/media/pci/saa7134/saa7134-video.c index 3abf527..7c503fb 100644 --- a/drivers/media/pci/saa7134/saa7134-video.c +++ b/drivers/media/pci/saa7134/saa7134-video.c @@ -2248,6 +2248,17 @@ static int saa7134_streamon(struct file *file, void *priv, if (!res_get(dev, fh, res)) return -EBUSY; + /* The SAA7134 has a 1K FIFO; the datasheet suggests that when + * configured conservatively, there's 22 usec of buffering for video. + * We therefore request a DMA latency of 20 usec, giving us 2 usec of + * margin in case the FIFO is configured differently to the datasheet. + * Unfortunately, I lack register-level documentation to check the + * Linux FIFO setup and confirm the perfect value. + */ + pm_qos_add_request(&fh->qos_request, + PM_QOS_CPU_DMA_LATENCY, + 20); + return videobuf_streamon(saa7134_queue(fh)); } @@ -2259,6 +2270,8 @@ static int saa7134_streamoff(struct file *file, void *priv, struct saa7134_dev *dev = fh->dev; int res = saa7134_resource(fh); + pm_qos_remove_request(&fh->qos_request); + err = videobuf_streamoff(saa7134_queue(fh)); if (err < 0) return err; |
