ACK: [PATCH 1/1] drm/radeon: prefer lower reference dividers

[Connor Kuehl]

On 6/17/19 8:10 PM, Kai-Heng Feng wrote:
> From: Christian König <christian.koenig at amd.com>
> 
> BugLink: https://bugs.launchpad.net/bugs/1791312
> 
> Instead of the closest reference divider prefer the lowest,
> this fixes flickering issues on HP Compaq nx9420.
> 
> Bugs: https://bugs.freedesktop.org/show_bug.cgi?id=108514
> Suggested-by: Paul Dufresne <dufresnep at gmail.com>
> Signed-off-by: Christian König <christian.koenig at amd.com>
> Acked-by: Alex Deucher <alexander.deucher at amd.com>
> Signed-off-by: Alex Deucher <alexander.deucher at amd.com>
> Cc: stable at vger.kernel.org
> (cherry picked from commit 2e26ccb119bde03584be53406bbd22e711b0d6e6)
> Signed-off-by: Kai-Heng Feng <kai.heng.feng at canonical.com>

Acked-by: Connor Kuehl <connor.kuehl at canonical.com>

> ---
>  drivers/gpu/drm/radeon/radeon_display.c | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c
> index 9d3ac8b981da..d8e2d7b3b836 100644
> --- a/drivers/gpu/drm/radeon/radeon_display.c
> +++ b/drivers/gpu/drm/radeon/radeon_display.c
> @@ -921,12 +921,12 @@ static void avivo_get_fb_ref_div(unsigned nom, unsigned den, unsigned post_div,
>  	ref_div_max = max(min(100 / post_div, ref_div_max), 1u);
>  
>  	/* get matching reference and feedback divider */
> -	*ref_div = min(max(DIV_ROUND_CLOSEST(den, post_div), 1u), ref_div_max);
> +	*ref_div = min(max(den/post_div, 1u), ref_div_max);
>  	*fb_div = DIV_ROUND_CLOSEST(nom * *ref_div * post_div, den);
>  
>  	/* limit fb divider to its maximum */
>  	if (*fb_div > fb_div_max) {
> -		*ref_div = DIV_ROUND_CLOSEST(*ref_div * fb_div_max, *fb_div);
> +		*ref_div = (*ref_div * fb_div_max)/(*fb_div);
>  		*fb_div = fb_div_max;
>  	}
>  }
> 


-- 
Connor
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