linux-kernel - RE: [PATCH 0/2] usb: host: Drop resume calls on {e,o}hci_platform

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Message-ID:
 <TY3PR01MB11346E9D561CAE53CF47F7C0886A5A@TY3PR01MB11346.jpnprd01.prod.outlook.com>
Date: Sun, 7 Dec 2025 16:47:54 +0000
From: Biju Das <biju.das.jz@...renesas.com>
To: Alan Stern <stern@...land.harvard.edu>, biju.das.au
	<biju.das.au@...il.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>, Philipp Zabel
	<p.zabel@...gutronix.de>, Claudiu Beznea <claudiu.beznea.uj@...renesas.com>,
	"linux-usb@...r.kernel.org" <linux-usb@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Geert
 Uytterhoeven <geert+renesas@...der.be>, Prabhakar Mahadev Lad
	<prabhakar.mahadev-lad.rj@...renesas.com>,
	"linux-renesas-soc@...r.kernel.org" <linux-renesas-soc@...r.kernel.org>
Subject: RE: [PATCH 0/2] usb: host: Drop resume calls on
 {e,o}hci_platform_suspend()

Hi Alan Stern,

Thanks for the feedback.

> -----Original Message-----
> From: Alan Stern <stern@...land.harvard.edu>
> Sent: 07 December 2025 16:36
> Subject: Re: [PATCH 0/2] usb: host: Drop resume calls on {e,o}hci_platform_suspend()
> 
> On Sun, Dec 07, 2025 at 12:47:25PM +0000, Biju wrote:
> > From: Biju Das <biju.das.jz@...renesas.com>
> >
> > As per the suspend_devices_and_enter() [1], if .suspend() fails, it
> > invoke the .resume() callback.
> 
> Quite wrong.  If .suspend() fails, the core assumes the device is still at full power.  It does not
> try to resume the device.

If there is a failure on any device it aborts suspend and jump to Resume_devices that
calls .resume_callback(). Please see failure logs of PWM device failure[2]

Recover_platform:
	platform_recover(state);
	goto Resume_devices;

> 
> > This patch series drops redundant resume() from
> > {e,o}hci_platform_suspend()
> 
> These resume() calls are not redundant and they should not be dropped.

ehci_resume() is called from both failure and resume path.
Maybe it is OK to call ehci_resume() twice. One from failure path and one from resume().

> 
> > [1]
> > https://elixir.bootlin.com/linux/v6.18-rc7/source/kernel/power/suspend
> > .c#L519
> 
> The message on this line has no bearing on what you are doing.  It merely says "Some devices failed to
> suspend, or early wake event detected".  There's nothing about invoking the .resume() callback.

See the logs[2] in case of failure.

[2]
[   47.965220] Filesystems sync: 0.000 seconds
[   47.971883] Freezing user space processes
[   47.977739] Freezing user space processes completed (elapsed 0.001 seconds)
[   47.984772] OOM killer disabled.
[   47.988065] Freezing remaining freezable tasks
[   47.993681] Freezing remaining freezable tasks completed (elapsed 0.001 seconds)
[   48.001143] printk: Suspending console(s) (use no_console_suspend to debug)
[   48.077166] renesas-gbeth 15c30000.ethernet end0: Link is Down
[   48.081846] pwm-rzg2l-gpt 13010000.pwm: PM: dpm_run_callback(): rzg2l_gpt_suspend [pwm_rzg2l_gpt] returns -110
[   48.081937] pwm-rzg2l-gpt 13010000.pwm: PM: failed to suspend: error -110
[   48.082157] PM: Some devices failed to suspend, or early wake event detected
[   48.091749] dwmac4: Master AXI performs any burst length
[   48.091829] renesas-gbeth 15c30000.ethernet end0: No Safety Features support found
[   48.091924] renesas-gbeth 15c30000.ethernet end0: IEEE 1588-2008 Advanced Timestamp supported
[   48.092073] renesas-gbeth 15c30000.ethernet end0: configuring for phy/rgmii-id link mode
[   48.100718] dwmac4: Master AXI performs any burst length
[   48.100791] renesas-gbeth 15c40000.ethernet end1: No Safety Features support found
[   48.100875] renesas-gbeth 15c40000.ethernet end1: IEEE 1588-2008 Advanced Timestamp supported
[   48.101016] renesas-gbeth 15c40000.ethernet end1: configuring for phy/rgmii-id link mode
[   48.149094] usb usb1: root hub lost power or was reset
[   48.149136] usb usb2: root hub lost power or was reset
[   48.361219] OOM killer enabled.
[   48.364360] Restarting tasks: Starting
[   48.369495] Restarting tasks: Done
[   48.372943] random: crng reseeded on system resumption
 PM: suspend exit
[   51.084906] renesas-gbeth 15c30000.ethernet end0: Link is Up - 1Gbps/Full - flow control rx/tx

Cheers,
Biju