[PATCH] drm/radeon: prefer lower reference dividers

[Deucher, Alexander]

Acked-by: Alex Deucher <alexander.deucher at amd.com>
________________________________
From: amd-gfx <amd-gfx-bounces at lists.freedesktop.org> on behalf of Christian König <ckoenig.leichtzumerken at gmail.com>
Sent: Monday, May 6, 2019 2:01 PM
To: amd-gfx at lists.freedesktop.org; dufresnep at gmail.com; werner.lueckel at googlemail.com
Subject: [PATCH] drm/radeon: prefer lower reference dividers

[CAUTION: External Email]

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>
---
 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;
        }
 }
--
2.17.1

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