clk: divider: read-only divider can propagate rate change

When a divider clock has CLK_DIVIDER_READ_ONLY set, it means that the
register shall be left un-touched, but it does not mean the clock
should stop rate propagation if CLK_SET_RATE_PARENT is set

This is properly handled in qcom clk-regmap-divider but it was not in
the generic divider

To fix this situation, introduce a new helper function
divider_ro_round_rate, on the same model as divider_round_rate.

Fixes: e6d5e7d90be9 ("clk-divider: Fix READ_ONLY when divider > 1")
Signed-off-by: Jerome Brunet <[e-mail]>
Tested-By: David Lechner <[e-mail]>
Signed-off-by: Michael Turquette <[e-mail]>
Signed-off-by: Stephen Boyd <[e-mail]>

drivers/clk/clk-divider.c

···
 }
 EXPORT_SYMBOL_GPL(divider_round_rate_parent);
 
+long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+				  unsigned long rate, unsigned long *prate,
+				  const struct clk_div_table *table, u8 width,
+				  unsigned long flags, unsigned int val)
+{
+	int div;
+
+	div = _get_div(table, val, flags, width);
+
+	/* Even a read-only clock can propagate a rate change */
+	if (clk_hw_get_flags(hw) & CLK_SET_RATE_PARENT) {
+		if (!parent)
+			return -EINVAL;
+
+		*prate = clk_hw_round_rate(parent, rate * div);
+	}
+
+	return DIV_ROUND_UP_ULL((u64)*prate, div);
+}
+EXPORT_SYMBOL_GPL(divider_ro_round_rate_parent);
+
+
 static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 				unsigned long *prate)
 {
 	struct clk_divider *divider = to_clk_divider(hw);
-	int bestdiv;
 
 	/* if read only, just return current value */
 	if (divider->flags & CLK_DIVIDER_READ_ONLY) {
-		bestdiv = clk_readl(divider->reg) >> divider->shift;
-		bestdiv &= clk_div_mask(divider->width);
-		bestdiv = _get_div(divider->table, bestdiv, divider->flags,
-			divider->width);
-		return DIV_ROUND_UP_ULL((u64)*prate, bestdiv);
+		u32 val;
+
+		val = clk_readl(divider->reg) >> divider->shift;
+		val &= clk_div_mask(divider->width);
+
+		return divider_ro_round_rate(hw, rate, prate, divider->table,
+					     divider->width, divider->flags,
+					     val);
 	}
 
 	return divider_round_rate(hw, rate, prate, divider->table,

include/linux/clk-provider.h

···
 			       unsigned long rate, unsigned long *prate,
 			       const struct clk_div_table *table,
 			       u8 width, unsigned long flags);
+long divider_ro_round_rate_parent(struct clk_hw *hw, struct clk_hw *parent,
+				  unsigned long rate, unsigned long *prate,
+				  const struct clk_div_table *table, u8 width,
+				  unsigned long flags, unsigned int val);
 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 		const struct clk_div_table *table, u8 width,
 		unsigned long flags);
···
 {
 	return divider_round_rate_parent(hw, clk_hw_get_parent(hw),
 					 rate, prate, table, width, flags);
+}
+
+static inline long divider_ro_round_rate(struct clk_hw *hw, unsigned long rate,
+					 unsigned long *prate,
+					 const struct clk_div_table *table,
+					 u8 width, unsigned long flags,
+					 unsigned int val)
+{
+	return divider_ro_round_rate_parent(hw, clk_hw_get_parent(hw),
+					    rate, prate, table, width, flags,
+					    val);
 }
 
 /*