linux-kernel - RE: [PATCH v2 0/2] reset: rzg2l-usbphy-ctrl: Add suspend to RAM support

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Message-ID:
 <TY3PR01MB11346D053263D4E4C367F1EA186A5A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Sun, 7 Dec 2025 11:02:38 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Claudiu.Beznea <claudiu.beznea@...on.dev>, "p.zabel@...gutronix.de"
	<p.zabel@...gutronix.de>
CC: "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>,
	Claudiu Beznea <claudiu.beznea.uj@...renesas.com>
Subject: RE: [PATCH v2 0/2] reset: rzg2l-usbphy-ctrl: Add suspend to RAM
 support

Hi Claudiu,

> -----Original Message-----
> From: Claudiu Beznea <claudiu.beznea@...on.dev>
> Sent: 05 December 2025 10:00
> Subject: Re: [PATCH v2 0/2] reset: rzg2l-usbphy-ctrl: Add suspend to RAM support
> 
> Hi, Biju,
> 
> On 12/5/25 10:53, Biju Das wrote:
> >
> >
> > Hi Claudiu,
> >
> >> -----Original Message-----
> >> From: Claudiu Beznea <claudiu.beznea@...on.dev>
> >> Sent: 04 December 2025 18:26
> >> Subject: Re: [PATCH v2 0/2] reset: rzg2l-usbphy-ctrl: Add suspend to
> >> RAM support
> >>
> >> Hi, Philipp,
> >>
> >> Could you please let me know if there's anything I should do for this series?
> >
> > If rzg2l_usbphy_ctrl_suspend() fails, What is the probability that it
> > will suspend again without any issue
> 
> How can I measure this?
> 
> The idea with this code was the following: if any instruction of suspend fails, the suspend is
> aborted, thus code in rzg2l_usbphy_ctrl_suspend() is trying to restore the runtime state of the HW so
> that no runtime users of it to be affected. This is also how core suspend code is doing, e.g.
> suspend_devices_and_enter().

After rechecking, the cleanup() in the suspend code making usage count unbalanced.

Eg:
 Suspend returns error with the following usage count incremented 

static int rzg2l_usbphy_ctrl_suspend(struct device *dev)
{
reset_deassert:
+	reset_control_deassert(priv->rstc);
+rpm_resume:
+	pm_runtime_resume_and_get(dev);
+	return ret;
}


The suspend error code invokes device resume[1] and in that you are again calling
reset_control_deassert() and pm_runtime_resume_and_get() which makes the usage
count unbalanced forever.

So, looks like the current logic in the Add suspend to RAM support patch is wrong.

[1]
https://elixir.bootlin.com/linux/v6.18-rc7/source/kernel/power/suspend.c#L519

static int rzg2l_usbphy_ctrl_resume(struct device *dev)
+{
+	ret = pm_runtime_resume_and_get(dev);
+
+	rzg2l_usbphy_ctrl_init(priv);
+}

Cheers,
Biju