linux-kernel - Re: [PATCH v3 1/5] clk: Respect CLK_OPS_PARENT

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Message-ID: <6678782.DvuYhMxLoT@workhorse>
Date: Wed, 28 Jan 2026 15:09:46 +0100
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: Mark Brown <broonie@...nel.org>
Cc: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Michael Turquette <mturquette@...libre.com>, Stephen Boyd <sboyd@...nel.org>,
 Dong Aisheng <aisheng.dong@....com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Yassine Oudjana <y.oudjana@...tonmail.com>,
 Laura Nao <laura.nao@...labora.com>,
 Nícolas F. R. A. Prado <nfraprado@...labora.com>,
 Chia-I Wu <olvaffe@...il.com>, Chen-Yu Tsai <wenst@...omium.org>,
 kernel@...labora.com, linux-clk@...r.kernel.org,
 linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
 linux-mediatek@...ts.infradead.org
Subject: Re: [PATCH v3 1/5] clk: Respect CLK_OPS_PARENT_ENABLE during recalc

On Wednesday, 28 January 2026 00:14:29 Central European Standard Time Mark Brown wrote:
> On Tue, Jan 27, 2026 at 07:18:02PM +0100, Nicolas Frattaroli wrote:
> 
> > Can someone let me know which clocks (with which parent) in those
> > affected devices is causing this? I'm wondering if this change
> > unmasked some undeclared dependency that it's now stumbling over
> > because it's enabling the parent earlier than ever.
> 
> Do you have a debugging patch we could run which would say which clocks
> are impacted?  I guess it's more of an issue for the platforms that give
> no output but for at least Avenger96 I was getting earlycon output.

Try this one
---
diff --git a/drivers/clk/clk.c b/drivers/clk/clk.c
index 1b0f9d567f48..fa1443517768 100644
--- a/drivers/clk/clk.c
+++ b/drivers/clk/clk.c
@@ -1921,13 +1921,21 @@ static unsigned long clk_recalc(struct clk_core *core,
 	unsigned long rate = parent_rate;

 	if (core->ops->recalc_rate && !clk_pm_runtime_get(core)) {
-		if (core->flags & CLK_OPS_PARENT_ENABLE)
+		if (core->flags & CLK_OPS_PARENT_ENABLE) {
+			pr_info("%s: enabling parent %s for %s\n", __func__,
+				core->parent ? core->parent->name : "(null)",
+				core->name);
 			clk_core_prepare_enable(core->parent);
+		}

 		rate = core->ops->recalc_rate(core->hw, parent_rate);

-		if (core->flags & CLK_OPS_PARENT_ENABLE)
+		if (core->flags & CLK_OPS_PARENT_ENABLE) {
+			pr_info("%s: disabling parent %s for %s\n", __func__,
+				core->parent ? core->parent->name : "(null)",
+				core->name);
 			clk_core_disable_unprepare(core->parent);
+		}

 		clk_pm_runtime_put(core);
 	}
@@ -4038,8 +4046,12 @@ static int __clk_core_init(struct clk_core *core)
 	 */
 	clk_core_update_duty_cycle_nolock(core);

-	if (core->flags & CLK_OPS_PARENT_ENABLE)
+	if (core->flags & CLK_OPS_PARENT_ENABLE) {
+		pr_info("%s: enabling parent %s for %s\n", __func__,
+			core->parent ? core->parent->name : "(null)",
+			core->name);
 		clk_core_prepare_enable(core->parent);
+	}

 	/*
 	 * Set clk's rate.  The preferred method is to use .recalc_rate.  For
@@ -4056,8 +4068,12 @@ static int __clk_core_init(struct clk_core *core)
 		rate = 0;
 	core->rate = core->req_rate = rate;

-	if (core->flags & CLK_OPS_PARENT_ENABLE)
+	if (core->flags & CLK_OPS_PARENT_ENABLE) {
+		pr_info("%s: disabling parent %s for %s\n", __func__,
+			core->parent ? core->parent->name : "(null)",
+			core->name);
 		clk_core_disable_unprepare(core->parent);
+	}

 	/*
 	 * Enable CLK_IS_CRITICAL clocks so newly added critical clocks
---

I don't remember if printk buffers are flushed after each invocation and
couldn't quickly find a kernel parameter to control this, but from
experience I think these prints should show up if it then hangs the SoC
on the very next line.

> > To not have me break everyone's -next for days on end, feel free
> > to drop this patch. MT8196, which this was added for, doesn't boot
> > with mainline yet anyway.
> 
> Please, this is making my test lab miserable.
> 

The good news is that the rest of the series can stay without doing
any harm if this single patch gets dropped, and I can re-attempt
this in the next cycle.

Kind regards,
Nicolas Frattaroli