[v4,49/68] clk: at91: smd: Switch to determine_rate

Commit Message

Maxime Ripard May 5, 2023, 11:25 a.m. UTC

The Atmel SAM9x5 SMD clocks implements a mux with a set_parent
hook, but doesn't provide a determine_rate implementation.

This is a bit odd, since set_parent() is there to, as its name implies,
change the parent of a clock. However, the most likely candidate to
trigger that parent change is a call to clk_set_rate(), with
determine_rate() figuring out which parent is the best suited for a
given rate.

The other trigger would be a call to clk_set_parent(), but it's far less
used, and it doesn't look like there's any obvious user for that clock.

So, the set_parent hook is effectively unused, possibly because of an
oversight. However, it could also be an explicit decision by the
original author to avoid any reparenting but through an explicit call to
clk_set_parent().

The driver does implement round_rate() though, which means that we can
change the rate of the clock, but we will never get to change the
parent.

However, It's hard to tell whether it's been done on purpose or not.

Since we'll start mandating a determine_rate() implementation, let's
convert the round_rate() implementation to a determine_rate(), which
will also make the current behavior explicit. And if it was an
oversight, the clock behaviour can be adjusted later on.

Cc: Alexandre Belloni <[e-mail]>
Cc: Claudiu Beznea <[e-mail]>
Cc: Nicolas Ferre <[e-mail]>
Cc: [e-mail]
Signed-off-by: Maxime Ripard <[e-mail]>
---
 drivers/clk/at91/clk-smd.c | 29 +++++++++++++++++------------
 1 file changed, 17 insertions(+), 12 deletions(-)

Patch

diff --git a/drivers/clk/at91/clk-smd.c b/drivers/clk/at91/clk-smd.c
index 160378438f1b..09c649c8598e 100644
--- a/drivers/clk/at91/clk-smd.c
+++ b/drivers/clk/at91/clk-smd.c
@@ -36,26 +36,31 @@  static unsigned long at91sam9x5_clk_smd_recalc_rate(struct clk_hw *hw,
 	return parent_rate / (smddiv + 1);
 }
 
-static long at91sam9x5_clk_smd_round_rate(struct clk_hw *hw, unsigned long rate,
-					  unsigned long *parent_rate)
+static int at91sam9x5_clk_smd_determine_rate(struct clk_hw *hw,
+					     struct clk_rate_request *req)
 {
 	unsigned long div;
 	unsigned long bestrate;
 	unsigned long tmp;
 
-	if (rate >= *parent_rate)
-		return *parent_rate;
+	if (req->rate >= req->best_parent_rate) {
+		req->rate = req->best_parent_rate;
+		return 0;
+	}
 
-	div = *parent_rate / rate;
-	if (div > SMD_MAX_DIV)
-		return *parent_rate / (SMD_MAX_DIV + 1);
+	div = req->best_parent_rate / req->rate;
+	if (div > SMD_MAX_DIV) {
+		req->rate = req->best_parent_rate / (SMD_MAX_DIV + 1);
+		return 0;
+	}
 
-	bestrate = *parent_rate / div;
-	tmp = *parent_rate / (div + 1);
-	if (bestrate - rate > rate - tmp)
+	bestrate = req->best_parent_rate / div;
+	tmp = req->best_parent_rate / (div + 1);
+	if (bestrate - req->rate > req->rate - tmp)
 		bestrate = tmp;
 
-	return bestrate;
+	req->rate = bestrate;
+	return 0;
 }
 
 static int at91sam9x5_clk_smd_set_parent(struct clk_hw *hw, u8 index)
@@ -98,7 +103,7 @@  static int at91sam9x5_clk_smd_set_rate(struct clk_hw *hw, unsigned long rate,
 
 static const struct clk_ops at91sam9x5_smd_ops = {
 	.recalc_rate = at91sam9x5_clk_smd_recalc_rate,
-	.round_rate = at91sam9x5_clk_smd_round_rate,
+	.determine_rate = at91sam9x5_clk_smd_determine_rate,
 	.get_parent = at91sam9x5_clk_smd_get_parent,
 	.set_parent = at91sam9x5_clk_smd_set_parent,
 	.set_rate = at91sam9x5_clk_smd_set_rate,