https://bugs.freedesktop.org/show_bug.cgi?id=87682
--- Comment #15 from Thom madeforspam@telfort.nl --- ok, i created a variation of the one liner patch that works without reverting any of the existing code:
This patch prevents fb from going lower than 140 Preventing noise/snow on display . (for RS780M + LVDS)
diff: @@ void radeon_compute_pll_avivo(struct radeon_pll *pll,
/* determine allowed feedback divider range */ -- fb_div_min = pll->min_feedback_div; ++ fb_div_min = max(pll->min_feedback_div, 140u); fb_div_max = pll->max_feedback_div;
if (pll->flags & RADEON_PLL_USE_FRAC_FB_DIV) { fb_div_min *= 10;
results in: [drm:radeon_compute_pll_avivo] 69300 - 69290, pll dividers - fb: 271.0 ref: 4, post 14
This "works for me (TM)"
But it would be good if someone could check if there are no "unforeseen consequences" to this patch. I don't know much about GPU stuff an I am not familiar with the code. (and yes I know: hardcoding values is definitely "not done")