pxa_dma_update_sg_tail() is called only once, runs exactly the same loop as the
caller and has to recalculate the last element in an sg-list, that the caller
has already calculated. Eliminate redundancy by merging the two loops and
re-using the calculated pointer. This also saves a bit of performance which is
always good during video-capture.
Signed-off-by: Guennadi Liakhovetski <g.liakhovetski@xxxxxx>
---
On Mon, 16 Mar 2009, Robert Jarzmik wrote:
> Guennadi Liakhovetski <g.liakhovetski@xxxxxx> writes:
>
> > pxa_dma_update_sg_tail is called only here, why not inline it and also put
> > inside one loop?
> As for the inline, I'm pretty sure you know it is automatically done by gcc.
>
> As for moving it inside the loop, that would certainly improve performance. Yet
> I find it more readable/maintainable that way, and will leave it. But I won't be
> bothered at all if you retransform it back to your view, that's up to you.
Robert, this is what I'm going to apply on top of your patch-series.
Please, object:-)
drivers/media/video/pxa_camera.c | 20 ++++++--------------
1 files changed, 6 insertions(+), 14 deletions(-)
diff --git a/drivers/media/video/pxa_camera.c b/drivers/media/video/pxa_camera.c
index cfa113c..c639845 100644
--- a/drivers/media/video/pxa_camera.c
+++ b/drivers/media/video/pxa_camera.c
@@ -566,15 +566,6 @@ static void pxa_dma_stop_channels(struct pxa_camera_dev *pcdev)
}
}
-static void pxa_dma_update_sg_tail(struct pxa_camera_dev *pcdev,
- struct pxa_buffer *buf)
-{
- int i;
-
- for (i = 0; i < pcdev->channels; i++)
- pcdev->sg_tail[i] = buf->dmas[i].sg_cpu + buf->dmas[i].sglen;
-}
-
static void pxa_dma_add_tail_buf(struct pxa_camera_dev *pcdev,
struct pxa_buffer *buf)
{
@@ -585,12 +576,13 @@ static void pxa_dma_add_tail_buf(struct pxa_camera_dev *pcdev,
buf_last_desc = buf->dmas[i].sg_cpu + buf->dmas[i].sglen;
buf_last_desc->ddadr = DDADR_STOP;
- if (!pcdev->sg_tail[i])
- continue;
- pcdev->sg_tail[i]->ddadr = buf->dmas[i].sg_dma;
- }
+ if (pcdev->sg_tail[i])
+ /* Link the new buffer to the old tail */
+ pcdev->sg_tail[i]->ddadr = buf->dmas[i].sg_dma;
- pxa_dma_update_sg_tail(pcdev, buf);
+ /* Update the channel tail */
+ pcdev->sg_tail[i] = buf_last_desc;
+ }
}
/**
--
1.5.4
--
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