On Sat, 14 Mar 2009, Robert Jarzmik wrote:
> The last buffer queued will often overrun, as the DMA chain
> is finished, and the time the dma irq handler is activated,
> the QIF fifos are filled by the sensor.
>
> The fix is to ignore the overrun condition on the last
> queued buffer, and restart the capture only on intermediate
> buffers of the chain.
>
> Moreover, a fix was added to the very unlikely condition
> where in YUV422P mode, one channel overruns while another
> completes at the very same time. The capture is restarted
> after the overrun as before, but the other channel
> completion is now ignored.
>
> Signed-off-by: Robert Jarzmik <robert.jarzmik@xxxxxxx>
> ---
> drivers/media/video/pxa_camera.c | 25 ++++++++++++++++++++-----
> 1 files changed, 20 insertions(+), 5 deletions(-)
>
> diff --git a/drivers/media/video/pxa_camera.c b/drivers/media/video/pxa_camera.c
> index a0ca982..35e54fc 100644
> --- a/drivers/media/video/pxa_camera.c
> +++ b/drivers/media/video/pxa_camera.c
> @@ -623,6 +623,7 @@ static void pxa_camera_stop_capture(struct pxa_camera_dev *pcdev)
> cicr0 = __raw_readl(pcdev->base + CICR0) & ~CICR0_ENB;
> __raw_writel(cicr0, pcdev->base + CICR0);
>
> + pcdev->active = NULL;
> dev_dbg(pcdev->dev, "%s\n", __func__);
> }
>
> @@ -696,7 +697,6 @@ static void pxa_camera_wakeup(struct pxa_camera_dev *pcdev,
>
> if (list_empty(&pcdev->capture)) {
> pxa_camera_stop_capture(pcdev);
> - pcdev->active = NULL;
> for (i = 0; i < pcdev->channels; i++)
> pcdev->sg_tail[i] = NULL;
> return;
> @@ -764,10 +764,20 @@ static void pxa_camera_dma_irq(int channel, struct pxa_camera_dev *pcdev,
> goto out;
> }
>
> - if (!pcdev->active) {
> - dev_err(pcdev->dev, "DMA End IRQ with no active buffer!\n");
> + /*
> + * pcdev->active should not be NULL in DMA irq handler.
> + *
> + * But there is one corner case : if capture was stopped due to an
> + * overrun of channel 1, and at that same channel 2 was completed.
> + *
> + * When handling the overrun in DMA irq for channel 1, we'll stop the
> + * capture and restart it (and thus set pcdev->active to NULL). But the
> + * DMA irq handler will already be pending for channel 2. So on entering
> + * the DMA irq handler for channel 2 there will be no active buffer, yet
> + * that is normal.
> + */
> + if (!pcdev->active)
> goto out;
> - }
>
> vb = &pcdev->active->vb;
> buf = container_of(vb, struct pxa_buffer, vb);
> @@ -778,7 +788,12 @@ static void pxa_camera_dma_irq(int channel, struct pxa_camera_dev *pcdev,
> status & DCSR_ENDINTR ? "EOF " : "", vb, DDADR(channel));
>
> if (status & DCSR_ENDINTR) {
> - if (camera_status & overrun) {
> + /*
> + * It's normal if the last frame creates an overrun, as there
> + * are no more DMA descriptors to fetch from QIF fifos
> + */
> + if (camera_status & overrun
> + && !list_is_last(pcdev->capture.next, &pcdev->capture)) {
> dev_dbg(pcdev->dev, "FIFO overrun! CISR: %x\n",
Please, put "&&" on the first line:-)
> camera_status);
> pxa_camera_stop_capture(pcdev);
> --
> 1.5.6.5
Thanks
Guennadi
---
Guennadi Liakhovetski, Ph.D.
Freelance Open-Source Software Developer
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