path: root/drivers/media/pci/saa7134
diff options
authorSimon Farnsworth <simon.farnsworth@onelan.co.uk>2012-12-10 08:35:09 -0300
committerMauro Carvalho Chehab <mchehab@redhat.com>2012-12-27 16:08:55 -0200
commit87739868944919beb4e6b3860c74355a114a54a1 (patch)
tree80c0dc7e9d427b9e56f669e8948f6f4307c1e78f /drivers/media/pci/saa7134
parente8d4237325a475b02594d1fd85bb67983f7d57b9 (diff)
[media] saa7134: Add pm_qos_request to fix video corruption
The SAA7134 appears to have trouble buffering more than one line of video when doing DMA. Rather than try to fix the driver to cope (as has been done by Andy Walls for the cx18 driver), put in a pm_qos_request to limit deep sleep exit latencies. The visible effect of not having this is that seemingly random lines are only partly transferred - if you feed in a static image, you see a portion of the image "flicker" into place. [mchehab@redhat.com: Fix ABI breakage due to some renames at pm_qos] Signed-off-by: Simon Farnsworth <simon.farnsworth@onelan.co.uk> Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
Diffstat (limited to 'drivers/media/pci/saa7134')
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,
+ 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;