[PATCH v1] clk: Only enable the parent clock if the clock was enabled before reparenting

[PATCH v1] clk: Only enable the parent clock if the clock was enabled before reparenting

[bigunclemax]

From: Maksim Kiselev <bigunclemax@gmail.com>

The current implementation of clk_set_parent() unconditionally enables
the new parent clock, even if the target clock was not previously enabled.

To avoid this implicit behavior, this patch adds a check for whether
the target clock has been enabled before parent enabling..

Fixes: ac30d90f336 ("clk: Ensure the parent clocks are enabled while reparenting")
Signed-off-by: Maksim Kiselev <bigunclemax@gmail.com>
---
 drivers/clk/clk-uclass.c | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/drivers/clk/clk-uclass.c b/drivers/clk/clk-uclass.c
index 4f35b90382f..0f6bf3e02ed 100644
--- a/drivers/clk/clk-uclass.c
+++ b/drivers/clk/clk-uclass.c
@@ -631,10 +631,12 @@ int clk_set_parent(struct clk *clk, struct clk *parent)
 	if (!ops->set_parent)
 		return -ENOSYS;
 
-	ret = clk_enable(parent);
-	if (ret && ret != -ENOSYS) {
-		printf("Cannot enable parent %s\n", parent->dev->name);
-		return ret;
+	if (clk->enable_count) {
+		ret = clk_enable(parent);
+		if (ret && ret != -ENOSYS) {
+			printf("Cannot enable parent %s\n", parent->dev->name);
+			return ret;
+		}
 	}
 
 	ret = ops->set_parent(clk, parent);
-- 
2.48.1

Re: [PATCH v1] clk: Only enable the parent clock if the clock was enabled before reparenting

[Miquel Raynal]

Hi,

On 29/08/2025 at 11:25:00 +03, bigunclemax@gmail.com wrote:

> From: Maksim Kiselev <bigunclemax@gmail.com>
>
> The current implementation of clk_set_parent() unconditionally enables
> the new parent clock, even if the target clock was not previously enabled.
>
> To avoid this implicit behavior, this patch adds a check for whether
> the target clock has been enabled before parent enabling..
>
> Fixes: ac30d90f336 ("clk: Ensure the parent clocks are enabled while reparenting")
> Signed-off-by: Maksim Kiselev <bigunclemax@gmail.com>

It took me a bit of time to understand your issue, but that sounds
legitimate indeed.

Reviewed-by: Miquel Raynal <miquel.raynal@bootlin.com>

Thanks,
Miquèl

Re: [PATCH v1] clk: Only enable the parent clock if the clock was enabled before reparenting

[Tom Rini]

On Fri, 29 Aug 2025 11:25:00 +0300, bigunclemax@gmail.com wrote:

> The current implementation of clk_set_parent() unconditionally enables
> the new parent clock, even if the target clock was not previously enabled.
> 
> To avoid this implicit behavior, this patch adds a check for whether
> the target clock has been enabled before parent enabling..
> 
> 
> [...]

Applied to u-boot/next, thanks!

[1/1] clk: Only enable the parent clock if the clock was enabled before reparenting
      commit: b493db39ea7fb1205d3a2df269352cb79874c1c7
-- 
Tom