drm/sun4i: hdmi: Check for unset best_parent in sun4i_tmds_determine_rate

It is possible that if there is no exact rate match and
"rounded = clk_hw_round_rate(parent, ideal)" gives high enough values
(e.g. if rounded is 2 * ideal) that the condition
"abs(rate - rounded / i) < abs(rate - best_parent / best_div)" is never
met and best_parent is never set. This results in req->rate and
req->best_parent_rate being assigned 0.

To avoid this, we set best_parent to the first calculated rate if it is
unset. The sun4i_tmds_calc_divider function already has a similar check.

Fixes: 9c5681011a0c ("drm/sun4i: Add HDMI support")
Signed-off-by: Jonathan Liu <net147@gmail.com>
Signed-off-by: Maxime Ripard <maxime.ripard@free-electrons.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20180109020323.11852-2-net147@gmail.com

diff --git a/drivers/gpu/drm/sun4i/sun4i_hdmi_tmds_clk.c b/drivers/gpu/drm/sun4i/sun4i_hdmi_tmds_clk.c
index dc332ea56f6c757e7f5b9e54331986698ebc31fc..4d235e5ea31c085fac3e6a6fd6fb372eb79a042b 100644 (file)
--- a/drivers/gpu/drm/sun4i/sun4i_hdmi_tmds_clk.c
+++ b/drivers/gpu/drm/sun4i/sun4i_hdmi_tmds_clk.c
@@ -102,7 +102,7 @@ static int sun4i_tmds_determine_rate(struct clk_hw *hw,
                                        goto out;
                                }
 
-                               if (abs(rate - rounded / i) <
+                               if (!best_parent || abs(rate - rounded / i) <
                                    abs(rate - best_parent / best_div)) {
                                        best_parent = rounded;
                                        best_div = i;