1 files changed, 35 insertions, 4 deletions

diff --git a/drivers/gpu/drm/sun4i/sun4i_dotclock.c b/drivers/gpu/drm/sun4i/sun4i_dotclock.c
index 3ff668cb463c..5b3463197c48 100644
--- a/drivers/gpu/drm/sun4i/sun4i_dotclock.c
+++ b/drivers/gpu/drm/sun4i/sun4i_dotclock.c
@@ -72,14 +72,40 @@ static unsigned long sun4i_dclk_recalc_rate(struct clk_hw *hw,
 static long sun4i_dclk_round_rate(struct clk_hw *hw, unsigned long rate,
                                   unsigned long *parent_rate)
 {
-        return *parent_rate / DIV_ROUND_CLOSEST(*parent_rate, rate);
+        unsigned long best_parent = 0;
+        u8 best_div = 1;
+        int i;
+
+        for (i = 6; i < 127; i++) {
+                unsigned long ideal = rate * i;
+                unsigned long rounded;
+
+                rounded = clk_hw_round_rate(clk_hw_get_parent(hw),
+                                            ideal);
+
+                if (rounded == ideal) {
+                        best_parent = rounded;
+                        best_div = i;
+                        goto out;
+                }
+
+                if ((rounded < ideal) && (rounded > best_parent)) {
+                        best_parent = rounded;
+                        best_div = i;
+                }
+        }
+
+out:
+        *parent_rate = best_parent;
+
+        return best_parent / best_div;
 }
 
 static int sun4i_dclk_set_rate(struct clk_hw *hw, unsigned long rate,
                                unsigned long parent_rate)
 {
         struct sun4i_dclk *dclk = hw_to_dclk(hw);
-        int div = DIV_ROUND_CLOSEST(parent_rate, rate);
+        u8 div = parent_rate / rate;
 
         return regmap_update_bits(dclk->regmap, SUN4I_TCON0_DCLK_REG,
                                   GENMASK(6, 0), div);
@@ -127,10 +153,14 @@ int sun4i_dclk_create(struct device *dev, struct sun4i_tcon *tcon)
         const char *clk_name, *parent_name;
         struct clk_init_data init;
         struct sun4i_dclk *dclk;
+        int ret;
 
         parent_name = __clk_get_name(tcon->sclk0);
-        of_property_read_string_index(dev->of_node, "clock-output-names", 0,
-                                      &clk_name);
+        ret = of_property_read_string_index(dev->of_node,
+                                            "clock-output-names", 0,
+                                            &clk_name);
+        if (ret)
+                return ret;
 
         dclk = devm_kzalloc(dev, sizeof(*dclk), GFP_KERNEL);
         if (!dclk)
@@ -140,6 +170,7 @@ int sun4i_dclk_create(struct device *dev, struct sun4i_tcon *tcon)
         init.ops = &sun4i_dclk_ops;
         init.parent_names = &parent_name;
         init.num_parents = 1;
+        init.flags = CLK_SET_RATE_PARENT;
 
         dclk->regmap = tcon->regs;
         dclk->hw.init = &init;