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Date: Fri, 15 May 2026 14:46:54 +0200
From: Lukas Wunner <lukas@wunner.de>
To: Bjorn Helgaas <helgaas@kernel.org>
Cc: sashiko-reviews@lists.linux.dev, linux-pci@vger.kernel.org,
	"Rafael J . Wysocki" <rafael@kernel.org>,
	Marco Nenciarini <mnencia@kcore.it>,
	Michal Winiarski <michal.winiarski@intel.com>,
	Ilpo Jarvinen <ilpo.jarvinen@linux.intel.com>,
	Eric Chanudet <echanude@redhat.com>,
	Jean Guyader <jean.guyader@gmail.com>,
	Alex Williamson <alex@shazbot.org>, Sinan Kaya <okaya@kernel.org>,
	Mario Limonciello <superm1@kernel.org>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	linux-kernel@vger.kernel.org, Bjorn Helgaas <bhelgaas@google.com>
Subject: Re: [PATCH v1] PCI: Wait for device readiness after D3hot ->
 D0uninitialized transition
Message-ID: <agcVvg1ntQPbivr9@wunner.de>
References: <20260514200625.C6877C2BCB3@smtp.kernel.org>
 <20260514213811.GA434353@bhelgaas>
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In-Reply-To: <20260514213811.GA434353@bhelgaas>

On Thu, May 14, 2026 at 04:38:11PM -0500, Bjorn Helgaas wrote:
> On Thu, May 14, 2026 at 08:06:25PM +0000, sashiko-bot@kernel.org wrote:
> > > +		if (!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET))
> > > +			pci_dev_wait(dev, "power up D3hot->D0uninitialized",
> > > +				     PCIE_RESET_READY_POLL_MS);
> > 
> > Is it safe to ignore the return value of pci_dev_wait() here?
> > 
> > If the device times out or disconnects, pci_dev_wait() returns -ENOTTY. By
> > ignoring this error, pci_power_up() continues, unconditionally sets
> > dev->current_state = PCI_D0, and can return success (1 for need_restore).
> > 
> > If pci_power_up() returns success, will callers like pci_back_from_sleep()
> > execute pci_restore_state() against an unresponsive device, which could
> > potentially trigger PCIe Master Aborts, AER events, or system crashes?
> > 
> > Should pci_power_up() propagate the error from pci_dev_wait() to prevent
> > this?
> 
> Good point.  I think it should look like this instead:
> 
>     if (state == PCI_D3hot) {
>             pci_dev_d3_sleep(dev);
>             if (!(pmcsr & PCI_PM_CTRL_NO_SOFT_RESET)) {
>                     ret = pci_dev_wait(dev, "power up D3hot->D0uninitialized",
>                                        PCIE_RESET_READY_POLL_MS);
>                     if (ret) {
>                             pci_err(dev, "Not ready after soft reset\n");
>                             dev->current_state = PCI_D3cold;
>                             return -EIO;
>                     }

pci_dev_wait() already emits a warning message on timeout, so the
additional pci_err() is probably not needed.  Otherwise the user
would see duplicate messages, i.e.:

  pci SSSS:BB:DD.F: not ready 60000ms after power up D3hot->D0uninitialized
  pci SSSS:BB:DD.F: Not ready after soft reset

Thanks,

Lukas