[Bug 87682] Horizontal lines in radeon driver on kernel 3.15 and upwards

[bugzilla-daemon at freedesktop.org]

https://bugs.freedesktop.org/show_bug.cgi?id=87682

--- Comment #15 from Thom <madeforspam at 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")

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