From mboxrd@z Thu Jan  1 00:00:00 1970
From: Liu Ying <Ying.Liu@freescale.com>
Subject: Re: [PATCH 01/11] staging: drm/imx: also allow to allocate only 2
	DMFC slots for DP full plane
Date: Fri, 11 Oct 2013 15:12:47 +0800
Message-ID: <5257A4EF.1070808@freescale.com>
References: <1381414726-13904-1-git-send-email-p.zabel@pengutronix.de>
	<1381414726-13904-2-git-send-email-p.zabel@pengutronix.de>
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To: Philipp Zabel <p.zabel@pengutronix.de>
Cc: devel@driverdev.osuosl.org, Fabio Estevam <fabio.estevam@freescale.com>, kernel@pengutronix.de, dri-devel@lists.freedesktop.org, Greg Kroah-Hartman <gregkh@linuxfoundation.org>
List-Id: dri-devel@lists.freedesktop.org

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.zabel@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