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From: Lukas Wunner <lukas@wunner.de>
To: lirongqing <lirongqing@baidu.com>
Cc: Bjorn Helgaas <bhelgaas@google.com>,
	Niklas Schnelle <schnelle@linux.ibm.com>,
	Farhan Ali <alifm@linux.ibm.com>,
	Manivannan Sadhasivam <manivannan.sadhasivam@oss.qualcomm.com>,
	Frank Li <Frank.Li@nxp.com>,
	linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] PCI: Only restore state that was successfully saved around a reset
Date: Tue, 10 Nov 2026 11:13:45 +0100	[thread overview]
Message-ID: <avLuWagPGyPhLYvl@wunner.de> (raw)
In-Reply-To: <20261110053348.2419-1-lirongqing@baidu.com>

On Tue, Nov 10, 2026 at 01:33:47PM +0800, lirongqing wrote:
> pci_dev_save_and_disable() returns early when config space is inaccessible,
> without saving anything, but pci_dev_restore() calls pci_restore_state()
> unconditionally and pci_restore_state() does not look at state_saved. After
> the reset makes config space accessible again, the all-zero or stale
> saved_config_space[] array is written back to the device, clearing Command,
> BARs and, for bridges, the bus number registers.
> 
> Clear state_saved when the save is skipped and only restore when a state
> was saved.

The state_saved flag is used internally by the PCI core for
suspend/resume.  If a driver calls pci_save_state() on suspend,
the flag is set and that tells the PCI core that the driver already
put the device into a lower power state, obviating the need for the
PCI core to do that.

Please do not use the flag for a completely different purpose.

Thanks,

Lukas

      parent reply	other threads:[~2026-11-10 10:13 UTC|newest]

Thread overview: 4+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-11-10  5:33 lirongqing
2026-11-10  5:33 ` [PATCH] PCI: Save the Root Port state before a platform-specific reset lirongqing
2026-11-10 10:16   ` Lukas Wunner
2026-11-10 10:13 ` Lukas Wunner [this message]

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