From: Kai-Heng Feng kai.heng.feng@canonical.com
[ Upstream commit fc8c70526bd30733ea8667adb8b8ffebea30a8ed ]
Commit 2e26ccb119bd ("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: 2e26ccb119bd ("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 Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/gpu/drm/radeon/radeon_display.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/radeon/radeon_display.c b/drivers/gpu/drm/radeon/radeon_display.c index b2334349799d1..f1de68340944b 100644 --- a/drivers/gpu/drm/radeon/radeon_display.c +++ b/drivers/gpu/drm/radeon/radeon_display.c @@ -928,7 +928,7 @@ 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) {