clk: divider: Implement and wire up .determine_rate by default

.determine_rate is meant to replace .round_rate. The former comes with a
benefit which is especially relevant on 32-bit systems: since
.determine_rate uses an "unsigned long" (compared to a "signed long"
which is used by .round_rate) the maximum value on 32-bit systems
increases from 2^31 (or approx. 2.14GHz) to 2^32 (or approx. 4.29GHz).

Implement .determine_rate in addition to .round_rate so drivers that are
using clk_divider_{ro_,}ops can benefit from this by default. Keep the
.round_rate callback for now since some drivers rely on
clk_divider_ops.round_rate being implemented.

Signed-off-by: Martin Blumenstingl <martin.blumenstingl@googlemail.com>
Link: https://lore.kernel.org/r/20210702225145.2643303-2-martin.blumenstingl@googlemail.com
Signed-off-by: Stephen Boyd <sboyd@kernel.org>

Author: xdarklight

drivers/clk/clk-divider.c

@@ -446,6 +446,27 @@ static long clk_divider_round_rate(struct clk_hw *hw, unsigned long rate,
 				  divider->width, divider->flags);
 }
 
+static int clk_divider_determine_rate(struct clk_hw *hw,
+				      struct clk_rate_request *req)
+{
+	struct clk_divider *divider = to_clk_divider(hw);
+
+	/* if read only, just return current value */
+	if (divider->flags & CLK_DIVIDER_READ_ONLY) {
+		u32 val;
+
+		val = clk_div_readl(divider) >> divider->shift;
+		val &= clk_div_mask(divider->width);
+
+		return divider_ro_determine_rate(hw, req, divider->table,
+						 divider->width,
+						 divider->flags, val);
+	}
+
+	return divider_determine_rate(hw, req, divider->table, divider->width,
+				      divider->flags);
+}
+
 int divider_get_val(unsigned long rate, unsigned long parent_rate,
 		    const struct clk_div_table *table, u8 width,
 		    unsigned long flags)
@@ -501,13 +522,15 @@ static int clk_divider_set_rate(struct clk_hw *hw, unsigned long rate,
 const struct clk_ops clk_divider_ops = {
 	.recalc_rate = clk_divider_recalc_rate,
 	.round_rate = clk_divider_round_rate,
+	.determine_rate = clk_divider_determine_rate,
 	.set_rate = clk_divider_set_rate,
 };
 EXPORT_SYMBOL_GPL(clk_divider_ops);
 
 const struct clk_ops clk_divider_ro_ops = {
 	.recalc_rate = clk_divider_recalc_rate,
 	.round_rate = clk_divider_round_rate,
+	.determine_rate = clk_divider_determine_rate,
 };
 EXPORT_SYMBOL_GPL(clk_divider_ro_ops);