linux-kernel - [PATCH v5 05/11] clk: sunxi-ng: Add helper function to find closest rate

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Message-Id: <20230806-pll-mipi_set_rate_parent-v5-5-db4f5ca33fc3@oltmanns.dev>
Date:   Sun, 06 Aug 2023 15:06:50 +0200
From:   Frank Oltmanns <frank@...manns.dev>
To:     Maxime Ripard <mripard@...nel.org>,
        Michael Turquette <mturquette@...libre.com>,
        Stephen Boyd <sboyd@...nel.org>, Chen-Yu Tsai <wens@...e.org>,
        Jernej Skrabec <jernej.skrabec@...il.com>,
        Samuel Holland <samuel@...lland.org>,
        Andre Przywara <andre.przywara@....com>,
        Roman Beranek <me@...y.cz>
Cc:     linux-clk@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
        linux-sunxi@...ts.linux.dev, linux-kernel@...r.kernel.org,
        Frank Oltmanns <frank@...manns.dev>
Subject: [PATCH v5 05/11] clk: sunxi-ng: Add helper function to find
 closest rate

The default behaviour of clocks in the sunxi-ng driver is to select a
clock rate that is closest to but less than the requested rate.

Add the ccu_is_better_rate() helper function that - depending on the
fact if thc CCU_FEATURE_CLOSEST_RATE flag is set - decides if a rate is
closer than another rate.

Acked-by: Maxime Ripard <mripard@...nel.org>
Signed-off-by: Frank Oltmanns <frank@...manns.dev>
---
 drivers/clk/sunxi-ng/ccu_common.c | 12 ++++++++++++
 drivers/clk/sunxi-ng/ccu_common.h |  5 +++++
 2 files changed, 17 insertions(+)

diff --git a/drivers/clk/sunxi-ng/ccu_common.c b/drivers/clk/sunxi-ng/ccu_common.c
index 8d28a7a079d0..8babce55302f 100644
--- a/drivers/clk/sunxi-ng/ccu_common.c
+++ b/drivers/clk/sunxi-ng/ccu_common.c
@@ -39,6 +39,18 @@ void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock)
 }
 EXPORT_SYMBOL_NS_GPL(ccu_helper_wait_for_lock, SUNXI_CCU);
 
+bool ccu_is_better_rate(struct ccu_common *common,
+			unsigned long target_rate,
+			unsigned long current_rate,
+			unsigned long best_rate)
+{
+	if (common->features & CCU_FEATURE_CLOSEST_RATE)
+		return abs(current_rate - target_rate) < abs(best_rate - target_rate);
+
+	return current_rate <= target_rate && current_rate > best_rate;
+}
+EXPORT_SYMBOL_NS_GPL(ccu_is_better_rate, SUNXI_CCU);
+
 /*
  * This clock notifier is called when the frequency of a PLL clock is
  * changed. In common PLL designs, changes to the dividers take effect
diff --git a/drivers/clk/sunxi-ng/ccu_common.h b/drivers/clk/sunxi-ng/ccu_common.h
index 5ad219f041d5..942a72c09437 100644
--- a/drivers/clk/sunxi-ng/ccu_common.h
+++ b/drivers/clk/sunxi-ng/ccu_common.h
@@ -53,6 +53,11 @@ struct sunxi_ccu_desc {
 
 void ccu_helper_wait_for_lock(struct ccu_common *common, u32 lock);
 
+bool ccu_is_better_rate(struct ccu_common *common,
+			unsigned long target_rate,
+			unsigned long current_rate,
+			unsigned long best_rate);
+
 struct ccu_pll_nb {
 	struct notifier_block	clk_nb;
 	struct ccu_common	*common;

-- 
2.41.0