linux-kernel - Re: [PATCH] PCI/PM: Put devices to low power state on shutdown

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Message-ID: <6685e124-4a7d-44bb-80a9-fc5fa51269a9@amd.com>
Date: Thu, 22 Aug 2024 14:28:05 -0500
From: Mario Limonciello <mario.limonciello@....com>
To: Kai-Heng Feng <kai.heng.feng@...onical.com>, bhelgaas@...gle.com
Cc: mika.westerberg@...ux.intel.com, linux-pci@...r.kernel.org,
 linux-pm@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] PCI/PM: Put devices to low power state on shutdown

On 7/12/2024 01:24, Kai-Heng Feng wrote:
> Some laptops wake up after poweroff when HP Thunderbolt Dock G4 is
> connected.
> 
> The following error message can be found during shutdown:
> pcieport 0000:00:1d.0: AER: Correctable error message received from 0000:09:04.0
> pcieport 0000:09:04.0: PCIe Bus Error: severity=Correctable, type=Data Link Layer, (Receiver ID)
> pcieport 0000:09:04.0:   device [8086:0b26] error status/mask=00000080/00002000
> pcieport 0000:09:04.0:    [ 7] BadDLLP
> 
> Calling aer_remove() during shutdown can quiesce the error message,
> however the spurious wakeup still happens.
> 
> The issue won't happen if the device is in D3 before system shutdown, so
> putting device to low power state before shutdown to solve the issue.
> 
> I don't have a sniffer so this is purely guesswork, however I believe
> putting device to low power state it's the right thing to do.

KH,

I did testing with your patch along with a few others, and found that it 
does the best job to put a majority of devices into a low power state 
properly.

I have the details of what happens at S5 outlined on this Gist:
https://gist.github.com/superm1/f8f81e52f5b1d55b64493fdaec38e31c

* KH column is this patch.
* ML column is 
https://lore.kernel.org/linux-usb/43594a1c-c0dd-4ae1-b2c4-f5198e3fe951@amd.com/T/#m03d0b36f86fb4722009b24a8ee547011128db80b
* FS column is 0fab972eef49 being applied again

I also have power testing data from an OEM's system that shows that it 
improves things well enough that a previously failing energy star 
certification is now passing.

Reviewed-by: Mario Limonciello <mario.limonciello@....com>
Tested-by: Mario Limonciello <mario.limonciello@....com>

> 
> Link: https://bugzilla.kernel.org/show_bug.cgi?id=219036
> Signed-off-by: Kai-Heng Feng <kai.heng.feng@...onical.com>
> ---
>   drivers/pci/pci-driver.c | 8 ++++++++
>   1 file changed, 8 insertions(+)
> 
> diff --git a/drivers/pci/pci-driver.c b/drivers/pci/pci-driver.c
> index af2996d0d17f..4c6f66f3eb54 100644
> --- a/drivers/pci/pci-driver.c
> +++ b/drivers/pci/pci-driver.c
> @@ -510,6 +510,14 @@ static void pci_device_shutdown(struct device *dev)
>   	if (drv && drv->shutdown)
>   		drv->shutdown(pci_dev);
>   
> +	/*
> +	 * If driver already changed device's power state, it can mean the
> +	 * wakeup setting is in place, or a workaround is used. Hence keep it
> +	 * as is.
> +	 */
> +	if (!kexec_in_progress && pci_dev->current_state == PCI_D0)
> +		pci_prepare_to_sleep(pci_dev);
> +
>   	/*
>   	 * If this is a kexec reboot, turn off Bus Master bit on the
>   	 * device to tell it to not continue to do DMA. Don't touch