queue-4.14/drm-radeon-prefer-lower-reference-dividers.patch

   1 From 2e26ccb119bde03584be53406bbd22e711b0d6e6 Mon Sep 17 00:00:00 2001
   2 From: =?UTF-8?q?Christian=20K=C3=B6nig?= <christian.koenig@amd.com>
   3 Date: Mon, 6 May 2019 19:57:52 +0200
   4 Subject: drm/radeon: prefer lower reference dividers
   5 MIME-Version: 1.0
   6 Content-Type: text/plain; charset=UTF-8
   7 Content-Transfer-Encoding: 8bit
   8
   9 From: Christian König <christian.koenig@amd.com>
  10
  11 commit 2e26ccb119bde03584be53406bbd22e711b0d6e6 upstream.
  12
  13 Instead of the closest reference divider prefer the lowest,
  14 this fixes flickering issues on HP Compaq nx9420.
  15
  16 Bugs: https://bugs.freedesktop.org/show_bug.cgi?id=108514
  17 Suggested-by: Paul Dufresne <dufresnep@gmail.com>
  18 Signed-off-by: Christian König <christian.koenig@amd.com>
  19 Acked-by: Alex Deucher <alexander.deucher@amd.com>
  20 Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
  21 Cc: stable@vger.kernel.org
  22 Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
  23
  24 ---
  25  drivers/gpu/drm/radeon/radeon_display.c |    4 ++--
  26  1 file changed, 2 insertions(+), 2 deletions(-)
  27
  28 --- a/drivers/gpu/drm/radeon/radeon_display.c
  29 +++ b/drivers/gpu/drm/radeon/radeon_display.c
  30 @@ -923,12 +923,12 @@ static void avivo_get_fb_ref_div(unsigne
  31         ref_div_max = max(min(100 / post_div, ref_div_max), 1u);
  32
  33         /* get matching reference and feedback divider */
  34 -       *ref_div = min(max(DIV_ROUND_CLOSEST(den, post_div), 1u), ref_div_max);
  35 +       *ref_div = min(max(den/post_div, 1u), ref_div_max);
  36         *fb_div = DIV_ROUND_CLOSEST(nom * *ref_div * post_div, den);
  37
  38         /* limit fb divider to its maximum */
  39         if (*fb_div > fb_div_max) {
  40 -               *ref_div = DIV_ROUND_CLOSEST(*ref_div * fb_div_max, *fb_div);
  41 +               *ref_div = (*ref_div * fb_div_max)/(*fb_div);
  42                 *fb_div = fb_div_max;
  43         }
  44  }