linux-kernel - Re: [PATCH 18/20] video: msm: Prevent DMA lockups when switching bit depths

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Date:	Mon, 21 Mar 2011 16:42:05 +0300
From:	Sergei Shtylyov <sshtylyov@...sta.com>
To:	Carl Vanderlip <carlv@...eaurora.org>
CC:	David Brown <davidb@...eaurora.org>,
	Daniel Walker <dwalker@...o99.com>,
	Bryan Huntsman <bryanh@...eaurora.org>,
	linux-fbdev@...r.kernel.org, Brian Swetland <swetland@...gle.com>,
	linux-arm-msm@...r.kernel.org, linux-kernel@...r.kernel.org,
	Colin Cross <ccross@...roid.com>,
	Rebecca Schultz Zavin <rebecca@...roid.com>,
	Dima Zavin <dima@...roid.com>,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 18/20] video: msm: Prevent DMA lockups when switching
 bit	depths

Hello.

Carl Vanderlip wrote:

> Forces the lcdc off and waits a frame vsync period to prevent the MDP DMA
> engine crashing if the DMA bit depth is changed.  A sleep cannot be used
> because lcdc_dma_start is called in irq context.

    Maybe I'm blind again but I don't see any waiting...

> Authors:
> Dima Zavin <dima@...roid.com>
> Rebecca Schultz Zavin <rebecca@...roid.com>
> Colin Cross <ccross@...roid.com>

> Signed-off-by: Carl Vanderlip <carlv@...eaurora.org>
> ---
>  drivers/video/msm/mdp.c |    7 +++++++
>  1 files changed, 7 insertions(+), 0 deletions(-)

> diff --git a/drivers/video/msm/mdp.c b/drivers/video/msm/mdp.c
> index b3f334ad..49d956a 100644
> --- a/drivers/video/msm/mdp.c
> +++ b/drivers/video/msm/mdp.c
> @@ -564,6 +564,13 @@ void mdp_hw_init(struct mdp_info *mdp)
>  	mdp_writel(mdp, 1, 0x60);
>  	mdp_writel(mdp, 1, MDP_EBI2_PORTMAP_MODE);
>  
> +	/* disable lcdc */
> +	mdp_writel(mdp, 0, MDP_LCDC_CTL);
> +	/* enable auto clock gating for all blocks by default */
> +	mdp_writel(mdp, 0xffffffff, MDP_CGC_EN);
> +	/* reset color/gamma correct parms */
> +	mdp_writel(mdp, 0, MDP_DMA_P_COLOR_CORRECT_CONFIG);
> +
>  	mdp_writel(mdp, 0, MDP_CMD_DEBUG_ACCESS_BASE + 0x01f8);
>  	mdp_writel(mdp, 0, MDP_CMD_DEBUG_ACCESS_BASE + 0x01fc);
>  	mdp_writel(mdp, 1, 0x60);

WBR, Sergei
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