linux-kernel - [PATCH 1/2] clk: Export clk_disable

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Message-ID: <20250821080333.27049-2-claudiu.beznea.uj@bp.renesas.com>
Date: Thu, 21 Aug 2025 11:03:31 +0300
From: Claudiu <claudiu.beznea@...on.dev>
To: mturquette@...libre.com,
	sboyd@...nel.org,
	geert+renesas@...der.be,
	linux@...linux.org.uk
Cc: claudiu.beznea@...on.dev,
	linux-renesas-soc@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	linux-clk@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: [PATCH 1/2] clk: Export clk_disable_unused()

From: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>

The Renesas RZ/G3S SoC has a suspend mode where power to most components is
turned off and RAM is switched to self-refresh. Resuming from this
low-power mode is done with the help of the bootloader. During resume, the
bootloader re-enables the clocks for the modules needed in the resume
process (e.g. SDHI or serial). After that, control is passed to Linux.

If Linux has not probed a driver for one of the modules enabled by the
bootloader, or if the module was previously in a runtime-suspended state,
the corresponding clocks remain enabled after resume, even though they have
no consumers or they were previously disabled.

To avoid keeping these clocks enabled unnecessarily, make the
clk_disable_unused() function available to other drivers. Drivers can then
call it during resume to disable any unused clocks.

Signed-off-by: Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
---
 drivers/clk/clk.c   |  9 +++++----
 include/linux/clk.h | 12 ++++++++++++
 2 files changed, 17 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index b821b2cdb155..5278030b0ad8 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1460,7 +1460,7 @@ static void clk_core_disable_unprepare(struct clk_core *core)
 	clk_core_unprepare_lock(core);
 }
 
-static void __init clk_unprepare_unused_subtree(struct clk_core *core)
+static void clk_unprepare_unused_subtree(struct clk_core *core)
 {
 	struct clk_core *child;
 
@@ -1485,7 +1485,7 @@ static void __init clk_unprepare_unused_subtree(struct clk_core *core)
 	}
 }
 
-static void __init clk_disable_unused_subtree(struct clk_core *core)
+static void clk_disable_unused_subtree(struct clk_core *core)
 {
 	struct clk_core *child;
 	unsigned long flags;
@@ -1526,7 +1526,7 @@ static void __init clk_disable_unused_subtree(struct clk_core *core)
 		clk_core_disable_unprepare(core->parent);
 }
 
-static bool clk_ignore_unused __initdata;
+static bool clk_ignore_unused;
 static int __init clk_ignore_unused_setup(char *__unused)
 {
 	clk_ignore_unused = true;
@@ -1534,7 +1534,7 @@ static int __init clk_ignore_unused_setup(char *__unused)
 }
 __setup("clk_ignore_unused", clk_ignore_unused_setup);
 
-static int __init clk_disable_unused(void)
+int clk_disable_unused(void)
 {
 	struct clk_core *core;
 	int ret;
@@ -1574,6 +1574,7 @@ static int __init clk_disable_unused(void)
 	return 0;
 }
 late_initcall_sync(clk_disable_unused);
+EXPORT_SYMBOL_GPL(clk_disable_unused);
 
 static int clk_core_determine_round_nolock(struct clk_core *core,
 					   struct clk_rate_request *req)
diff --git a/include/linux/clk.h b/include/linux/clk.h
index b607482ca77e..7eb0e5eb9aba 100644
--- a/include/linux/clk.h
+++ b/include/linux/clk.h
@@ -950,6 +950,13 @@ int clk_save_context(void);
  */
 void clk_restore_context(void);
 
+/**
+ * clk_disable_unused - disable unused clocks
+ *
+ * Disable unused clocks at boot or resume time.
+ */
+int clk_disable_unused(void);
+
 #else /* !CONFIG_HAVE_CLK */
 
 static inline struct clk *clk_get(struct device *dev, const char *id)
@@ -1136,6 +1143,11 @@ static inline int clk_save_context(void)
 
 static inline void clk_restore_context(void) {}
 
+static inline int clk_disbale_unused(void)
+{
+	return 0;
+}
+
 #endif
 
 /* clk_prepare_enable helps cases using clk_enable in non-atomic context. */
-- 
2.43.0