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drm/radeon: Prefer lower feedback dividers

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Commit 2e26ccb119 ("drm/radeon: prefer lower reference dividers")
fixed screen flicker for HP Compaq nx9420 but breaks other laptops like
Asus X50SL.

Turns out we also need to favor lower feedback dividers.

Users confirmed this change fixes the regression and doesn't regress the
original fix.

Fixes: 2e26ccb119 ("drm/radeon: prefer lower reference dividers")
BugLink: https://bugs.launchpad.net/bugs/1791312
BugLink: https://bugs.launchpad.net/bugs/1861554
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Kai-Heng Feng <kai.heng.feng@canonical.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Kai-Heng Feng 2020-08-26 01:33:48 +08:00 committed by Alex Deucher
parent d98299885c
commit fc8c70526b
1 changed files with 1 additions and 1 deletions
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2
drivers/gpu/drm/radeon/radeon_display.c
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@ -933,7 +933,7 @@ static void avivo_get_fb_ref_div(unsigned nom, unsigned den, unsigned post_div,
/* get matching reference and feedback divider */
*ref_div = min(max(den/post_div, 1u), ref_div_max);
*fb_div = DIV_ROUND_CLOSEST(nom * *ref_div * post_div, den);
*fb_div = max(nom * *ref_div * post_div / den, 1u);
/* limit fb divider to its maximum */
if (*fb_div > fb_div_max) {