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From:   Maxime Ripard <maxime@cerno.tech>
Date:   Tue, 04 Apr 2023 12:11:50 +0200
Subject: [PATCH v3 60/65] clk: stm32: composite: Switch to determine_rate
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To:     Michael Turquette <mturquette@baylibre.com>,
        Stephen Boyd <sboyd@kernel.org>,
        =?utf-8?q?Andreas_F=C3=A4rber?= <afaerber@suse.de>,
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        Maxime Coquelin <mcoquelin.stm32@gmail.com>,
        Alexandre Torgue <alexandre.torgue@foss.st.com>,
        Luca Ceresoli <luca.ceresoli@bootlin.com>,
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        Liam Girdwood <lgirdwood@gmail.com>,
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Cc:     linux-clk@vger.kernel.org, linux-kernel@vger.kernel.org,
        AngeloGioacchino Del Regno 
        <angelogioacchino.delregno@collabora.com>,
        linux-arm-kernel@lists.infradead.org,
        linux-actions@lists.infradead.org, patches@opensource.cirrus.com,
        linux-stm32@st-md-mailman.stormreply.com,
        linux-mediatek@lists.infradead.org,
        linux-renesas-soc@vger.kernel.org, linux-tegra@vger.kernel.org,
        dri-devel@lists.freedesktop.org, linux-phy@lists.infradead.org,
        linux-rtc@vger.kernel.org, linux-sunxi@lists.linux.dev,
        alsa-devel@alsa-project.org, linux-mips@vger.kernel.org,
        Maxime Ripard <maxime@cerno.tech>
Precedence: bulk

The STM32 composite 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.

Signed-off-by: Maxime Ripard <maxime@cerno.tech>
---
 drivers/clk/stm32/clk-stm32-core.c | 32 +++++++++++++++++++++-----------
 1 file changed, 21 insertions(+), 11 deletions(-)

diff --git a/drivers/clk/stm32/clk-stm32-core.c b/drivers/clk/stm32/clk-stm32-core.c
index 3247539683c9..d5aa09e9fce4 100644
--- a/drivers/clk/stm32/clk-stm32-core.c
+++ b/drivers/clk/stm32/clk-stm32-core.c
@@ -426,15 +426,15 @@ static unsigned long clk_stm32_composite_recalc_rate(struct clk_hw *hw,
 				      composite->div_id, parent_rate);
 }
 
-static long clk_stm32_composite_round_rate(struct clk_hw *hw, unsigned long rate,
-					   unsigned long *prate)
+static int clk_stm32_composite_determine_rate(struct clk_hw *hw,
+					      struct clk_rate_request *req)
 {
 	struct clk_stm32_composite *composite = to_clk_stm32_composite(hw);
-
 	const struct stm32_div_cfg *divider;
+	unsigned long rate;
 
 	if (composite->div_id == NO_STM32_DIV)
-		return rate;
+		return 0;
 
 	divider = &composite->clock_data->dividers[composite->div_id];
 
@@ -445,14 +445,24 @@ static long clk_stm32_composite_round_rate(struct clk_hw *hw, unsigned long rate
 		val =  readl(composite->base + divider->offset) >> divider->shift;
 		val &= clk_div_mask(divider->width);
 
-		return divider_ro_round_rate(hw, rate, prate, divider->table,
-				divider->width, divider->flags,
-				val);
+		rate = divider_ro_round_rate(hw, req->rate, &req->best_parent_rate,
+					     divider->table, divider->width, divider->flags,
+					     val);
+		if (rate < 0)
+			return rate;
+
+		req->rate = rate;
+		return 0;
 	}
 
-	return divider_round_rate_parent(hw, clk_hw_get_parent(hw),
-					 rate, prate, divider->table,
-					 divider->width, divider->flags);
+	rate = divider_round_rate_parent(hw, clk_hw_get_parent(hw),
+					 req->rate, &req->best_parent_rate,
+					 divider->table, divider->width, divider->flags);
+	if (rate < 0)
+		return rate;
+
+	req->rate = rate;
+	return 0;
 }
 
 static u8 clk_stm32_composite_get_parent(struct clk_hw *hw)
@@ -602,7 +612,7 @@ static void clk_stm32_composite_disable_unused(struct clk_hw *hw)
 const struct clk_ops clk_stm32_composite_ops = {
 	.set_rate	= clk_stm32_composite_set_rate,
 	.recalc_rate	= clk_stm32_composite_recalc_rate,
-	.round_rate	= clk_stm32_composite_round_rate,
+	.determine_rate	= clk_stm32_composite_determine_rate,
 	.get_parent	= clk_stm32_composite_get_parent,
 	.set_parent	= clk_stm32_composite_set_parent,
 	.enable		= clk_stm32_composite_gate_enable,

-- 
2.39.2