diff options
| -rw-r--r-- | drivers/media/pci/saa7134/saa7134-video.c | 13 | ||||
| -rw-r--r-- | drivers/media/pci/saa7134/saa7134.h | 2 |
2 files changed, 15 insertions, 0 deletions
diff --git a/drivers/media/pci/saa7134/saa7134-video.c b/drivers/media/pci/saa7134/saa7134-video.c index 3abf52711e13..7c503fb68526 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; diff --git a/drivers/media/pci/saa7134/saa7134.h b/drivers/media/pci/saa7134/saa7134.h index c24b6512bd8f..0a3feaa8589b 100644 --- a/drivers/media/pci/saa7134/saa7134.h +++ b/drivers/media/pci/saa7134/saa7134.h @@ -29,6 +29,7 @@ #include <linux/notifier.h> #include <linux/delay.h> #include <linux/mutex.h> +#include <linux/pm_qos.h> #include <asm/io.h> @@ -469,6 +470,7 @@ struct saa7134_fh { enum v4l2_buf_type type; unsigned int resources; enum v4l2_priority prio; + struct pm_qos_request qos_request; /* video overlay */ struct v4l2_window win; |