[PATCH v2 6/8] clk: renesas: rcar-gen2: Switch Z clock to .determine_rate()

[Geert Uytterhoeven <geert+renesas@xxxxxxxxx>]

As the .round_rate() callback returns a long clock rate, it cannot
return clock rates that do not fit in signed long, but do fit in
unsigned long.  Hence switch the Z clock on R-Car Gen2 from the old
.round_rate() callback to the newer .determine_rate() callback, which
does not suffer from this limitation.

This includes implementing range checking.

Signed-off-by: Geert Uytterhoeven <geert+renesas@xxxxxxxxx>
---
v2:
  - Use div_u64() for division by unsigned long,
  - Rebased.
---
 drivers/clk/renesas/rcar-gen2-cpg.c | 23 +++++++++++++----------
 1 file changed, 13 insertions(+), 10 deletions(-)

diff --git a/drivers/clk/renesas/rcar-gen2-cpg.c b/drivers/clk/renesas/rcar-gen2-cpg.c
index c378505830f0bacc..d4fa3dc3e2a2632f 100644
--- a/drivers/clk/renesas/rcar-gen2-cpg.c
+++ b/drivers/clk/renesas/rcar-gen2-cpg.c
@@ -63,19 +63,22 @@ static unsigned long cpg_z_clk_recalc_rate(struct clk_hw *hw,
 	return div_u64((u64)parent_rate * mult, 32);
 }
 
-static long cpg_z_clk_round_rate(struct clk_hw *hw, unsigned long rate,
-				 unsigned long *parent_rate)
+static int cpg_z_clk_determine_rate(struct clk_hw *hw,
+				    struct clk_rate_request *req)
 {
-	unsigned long prate  = *parent_rate;
-	unsigned int mult;
+	unsigned long prate = req->best_parent_rate;
+	unsigned int min_mult, max_mult, mult;
 
-	if (!prate)
-		prate = 1;
+	min_mult = max(div64_ul(req->min_rate * 32ULL, prate), 1ULL);
+	max_mult = min(div64_ul(req->max_rate * 32ULL, prate), 32ULL);
+	if (max_mult < min_mult)
+		return -EINVAL;
 
-	mult = div64_ul(rate * 32ULL, prate);
-	mult = clamp(mult, 1U, 32U);
+	mult = div64_ul(req->rate * 32ULL, prate);
+	mult = clamp(mult, min_mult, max_mult);
 
-	return div_u64((u64)*parent_rate * mult, 32);
+	req->rate = div_u64((u64)prate * mult, 32);
+	return 0;
 }
 
 static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
@@ -126,7 +129,7 @@ static int cpg_z_clk_set_rate(struct clk_hw *hw, unsigned long rate,
 
 static const struct clk_ops cpg_z_clk_ops = {
 	.recalc_rate = cpg_z_clk_recalc_rate,
-	.round_rate = cpg_z_clk_round_rate,
+	.determine_rate = cpg_z_clk_determine_rate,
 	.set_rate = cpg_z_clk_set_rate,
 };
 
-- 
2.17.1