Hi Philipp,

On 10/10/2013 10:18 PM, Philipp Zabel wrote:
> Connecting a 320x240 parallel display on i.MX6 resulted in an invalid DRDY
> signal because the DC would not receive NL/EOL events on every line.
> Reducing the allocated DMFC space from 4 slots (256 * 128-bit) to 2 slots
> (128 * 128-bit) solved the problem.
> 
> Signed-off-by: Philipp Zabel <p.za...@pengutronix.de>
> ---
>  drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c | 8 ++++----
>  1 file changed, 4 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c 
> b/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
> index 2e97c33..98070dd 100644
> --- a/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
> +++ b/drivers/staging/imx-drm/ipu-v3/ipu-dmfc.c
> @@ -307,13 +307,13 @@ int ipu_dmfc_alloc_bandwidth(struct dmfc_channel *dmfc,
>               goto out;
>       }
>  
> -     /* Always allocate at least 128*4 bytes (2 slots) */
> -     if (slots < 2)
> -             slots = 2;
> -
>       /* For the MEM_BG channel, first try to allocate twice the slots */
>       if (dmfc->data->ipu_channel == IPUV3_CHANNEL_MEM_BG_SYNC)
>               segment = dmfc_find_slots(priv, slots * 2);
> +     else if (slots < 2)
> +             /* Always allocate at least 128*4 bytes (2 slots) */

The commit message mentions that the size of 2 slots is 128*128-bit, that is, 
128*16-byte.
This contradicts the above annotation(128*4 bytes (2 slots)).

> +             slots = 2;
> +
>       if (segment >= 0)
>               slots *= 2;
>       else
> 

Regards,
Liu Ying

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