Re: [PATCH] omap_vout: Fix "DMA transaction error" issue when rotation is enabled

[Laurent Pinchart <laurent.pinchart@ideasonboard.com>]

Hi Vaibhav,

On Friday 09 March 2012 17:41:57 Vaibhav Hiremath wrote:
> When rotation is enabled and driver is configured in USERPTR
> buffer exchange mechanism, in specific use-case driver reports
> an error,
>    "DMA transaction error with device 0".
> 
> In driver _buffer_prepare funtion, we were using
> "vout->buf_phy_addr[vb->i]" for buffer physical address to
> configure SDMA channel, but this variable does get updated
> only during init.
> And the issue will occur when driver allocates less number
> of buffers during init and application requests more buffers
> through REQBUF ioctl; this variable will lead to invalid
> configuration of SDMA channel leading to DMA transaction error.
> 
> Signed-off-by: Vaibhav Hiremath <hvaibhav@ti.com>
> ---
> Archit/Laurent,
> Can you help me to validate this patch on your platform/usecase?

I've tested the patch by rotating the omap_vout overlay by 90 degrees and 
starting a video stream with 4 buffers. There's no crash, but the kernel 
prints

[77.877807] omapdss DISPC error: FIFO UNDERFLOW on gfx, disabling the overlay
[77.928344] omapdss DISPC error: FIFO UNDERFLOW on vid1, disabling the overlay

The same problem occurs with 3 buffers, which is what the omap_vout driver 
allocates by default.

Without your patch applied I get the same behaviour. Is my test procedure 
wrong ?

>  drivers/media/video/omap/omap_vout_vrfb.c |    2 +-
>  1 files changed, 1 insertions(+), 1 deletions(-)
> 
> diff --git a/drivers/media/video/omap/omap_vout_vrfb.c
> b/drivers/media/video/omap/omap_vout_vrfb.c index 4be26ab..240d36d 100644
> --- a/drivers/media/video/omap/omap_vout_vrfb.c
> +++ b/drivers/media/video/omap/omap_vout_vrfb.c
> @@ -225,7 +225,7 @@ int omap_vout_prepare_vrfb(struct omap_vout_device
> *vout, if (!is_rotation_enabled(vout))
>  		return 0;
> 
> -	dmabuf = vout->buf_phy_addr[vb->i];
> +	dmabuf = (dma_addr_t) vout->queued_buf_addr[vb->i];
>  	/* If rotation is enabled, copy input buffer into VRFB
>  	 * memory space using DMA. We are copying input buffer
>  	 * into VRFB memory space of desired angle and DSS will

-- 
Regards,

Laurent Pinchart