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drm/radeon: prefer lower reference dividers

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commit 2e26ccb119bde03584be53406bbd22e711b0d6e6 upstream.

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@gmail.com>
Signed-off-by: Christian König <christian.koenig@amd.com>
Acked-by: Alex Deucher <alexander.deucher@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Cc: stable@vger.kernel.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian König 2019-05-06 19:57:52 +02:00 committed by Greg Kroah-Hartman
parent 748a97ec6c
commit 84c82ab8f1
1 changed files with 2 additions and 2 deletions
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4
drivers/gpu/drm/radeon/radeon_display.c
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@ -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;
}
}