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

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Message-ID: <5791016.31r3eYUQgx@workhorse>
Date: Wed, 28 Jan 2026 15:11:33 +0100
From: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
To: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
 Chen-Yu Tsai <wenst@...omium.org>, Chia-I Wu <olvaffe@...il.com>,
 Dong Aisheng <aisheng.dong@....com>, Laura Nao <laura.nao@...labora.com>,
 Matthias Brugger <matthias.bgg@...il.com>,
 Michael Turquette <mturquette@...libre.com>,
 Nícolas F.  R.  A. Prado <nfraprado@...labora.com>,
 Yassine Oudjana <y.oudjana@...tonmail.com>, Stephen Boyd <sboyd@...nel.org>,
 Alexander Stein <alexander.stein@...tq-group.com>
Cc: 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 RESEND v3 1/5] clk: Respect CLK_OPS_PARENT_ENABLE during recalc

On Tuesday, 27 January 2026 15:55:29 Central European Standard Time Alexander Stein wrote:
> Hello,
> 
> Am Freitag, 23. Januar 2026, 02:45:33 CET schrieb Stephen Boyd:
> > Quoting Nicolas Frattaroli (2025-12-15 03:23:58)
> > > When CLK_OPS_PARENT_ENABLE was introduced, it guarded various clock
> > > operations, such as setting the rate or switching parents. However,
> > > another operation that can and often does touch actual hardware state is
> > > recalc_rate, which may also be affected by such a dependency.
> > > 
> > > Add parent enables/disables where the recalc_rate op is called directly.
> > > 
> > > Fixes: fc8726a2c021 ("clk: core: support clocks which requires parents enable (part 2)")
> > > Fixes: a4b3518d146f ("clk: core: support clocks which requires parents enable (part 1)")
> > > Reviewed-by: AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>
> > > Reviewed-by: Chen-Yu Tsai <wenst@...omium.org>
> > > Signed-off-by: Nicolas Frattaroli <nicolas.frattaroli@...labora.com>
> > > ---
> > 
> > Applied to clk-next
> 
> Unfortunately this breaks my board TQMa8MPxL+MBa8MPxL on next-20260126.
> Last lines on bootlog (earlycon is necessary)
> > [    1.175639] Initialise system trusted keyrings
> > [    1.178907] workingset: timestamp_bits=42 max_order=19 bucket_order=0
> > [    1.185822] NFS: Registering the id_resolver key type
> > [    1.190295] Key type id_resolver registered
> > [    1.194473] Key type id_legacy registered
> > [    1.198515] nfs4filelayout_init: NFSv4 File Layout Driver Registering...
> > [    1.205235] nfs4flexfilelayout_init: NFSv4 Flexfile Layout Driver
> > Registering... [    1.213235] cryptd: max_cpu_qlen set to 1000
> > [    1.274689] Key type asymmetric registered
> > [    1.275939] Asymmetric key parser 'x509' registered
> > [    1.280896] Block layer SCSI generic (bsg) driver version 0.4 loaded
> > (major 242) [    1.288278] io scheduler mq-deadline registered
> > [    1.292840] io scheduler kyber registered
> > [    1.299245] ledtrig-cpu: registered to indicate activity on CPUs
> 
> Reverting commit 669917676e93fca5ea3c66fc9539830312bec58e fixes the problem.

Hi Alexander,

sorry for breaking -next.

Can you try the following patch to print which clock+parent is causing
the hang on your platform?

---
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
---

Thanks for reporting this.

Kind regards,
Nicolas Frattaroli

> 
> Best regards,
> Alexander
>