linux-kernel - Re: [PATCH 3/3] mx3fb: avoid screen flash when panning with fb_set

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Date:	Mon, 2 Jul 2012 10:18:33 +0800
From:	Liu Ying <liu.y.victor@...il.com>
To:	g.liakhovetski@....de
Cc:	Liu Ying <Ying.Liu@...escale.com>, FlorianSchandinat@....de,
	linux-fbdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH 3/3] mx3fb: avoid screen flash when panning with fb_set_var

Hi, Guennadi,

Could you please review the second(2/3) patch and the third(3/3) patch
of this series?
I have addressed your comments you gave in the previous review cycle.

Thanks.

2012/6/11, Liu Ying <Ying.Liu@...escale.com>:
> Users may call FBIOPUT_VSCREENINFO ioctrl to do pan display.
> This ioctrl relies on fb_set_var() to do the job. fb_set_var()
> calls custom fb_set_par() method and then calls custom
> fb_pan_display() method. The current implementation of mx3fb
> reinitializes IPU display controller every time the custom
> fb_set_par() method is called, which makes the screen flash
> if fb_set_var() is called to do panning frequently. This patch
> compares the new var info with the cached old one to decide
> whether we really need to reinitialize IPU display controller.
> We ignore xoffset and yoffset update because it doesn't require
> to reinitialize the controller. Users may specify activate field
> of var info with FB_ACTIVATE_NOW and FB_ACTIVATE_FORCE to
> reinialize the controller by force.
>
> Signed-off-by: Liu Ying <Ying.Liu@...escale.com>
> ---
>  drivers/video/mx3fb.c |   22 +++++++++++++++++++++-
>  1 files changed, 21 insertions(+), 1 deletions(-)
>
> diff --git a/drivers/video/mx3fb.c b/drivers/video/mx3fb.c
> index 2dd11c4..7d0aa7b 100644
> --- a/drivers/video/mx3fb.c
> +++ b/drivers/video/mx3fb.c
> @@ -721,6 +721,26 @@ static void mx3fb_dma_done(void *arg)
>  	complete(&mx3_fbi->flip_cmpl);
>  }
>
> +static bool mx3fb_must_set_par(struct fb_info *fbi)
> +{
> +	struct mx3fb_info *mx3_fbi = fbi->par;
> +	struct fb_var_screeninfo old_var = mx3_fbi->cur_var;
> +	struct fb_var_screeninfo new_var = fbi->var;
> +
> +	if ((fbi->var.activate & FB_ACTIVATE_FORCE) &&
> +	    (fbi->var.activate & FB_ACTIVATE_MASK) == FB_ACTIVATE_NOW)
> +		return true;
> +
> +	/*
> +	 * Ignore xoffset and yoffset update,
> +	 * because pan display handles this case.
> +	 */
> +	old_var.xoffset = new_var.xoffset;
> +	old_var.yoffset = new_var.yoffset;
> +
> +	return !!memcmp(&old_var, &new_var, sizeof(struct fb_var_screeninfo));
> +}
> +
>  static int __set_par(struct fb_info *fbi, bool lock)
>  {
>  	u32 mem_len, cur_xoffset, cur_yoffset;
> @@ -844,7 +864,7 @@ static int mx3fb_set_par(struct fb_info *fbi)
>
>  	mutex_lock(&mx3_fbi->mutex);
>
> -	ret = __set_par(fbi, true);
> +	ret = mx3fb_must_set_par(fbi) ? __set_par(fbi, true) : 0;
>
>  	mutex_unlock(&mx3_fbi->mutex);
>
> --
> 1.7.1
>
>
>


-- 
Best Regards,
Liu Ying
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