linux-kernel - Re: [PATCH v4 3/4] PCI: Decouple D3Hot and D3Cold handling for bridges

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Message-ID: <20240805153546.GE7274@thinkpad>
Date: Mon, 5 Aug 2024 21:05:46 +0530
From: Manivannan Sadhasivam <manivannan.sadhasivam@...aro.org>
To: Hsin-Yi Wang <hsinyi@...omium.org>
Cc: Bjorn Helgaas <bhelgaas@...gle.com>,
	"Rafael J. Wysocki" <rafael@...nel.org>,
	Len Brown <lenb@...nel.org>, linux-pci@...r.kernel.org,
	linux-kernel@...r.kernel.org, linux-acpi@...r.kernel.org,
	lukas@...ner.de, mika.westerberg@...ux.intel.com
Subject: Re: [PATCH v4 3/4] PCI: Decouple D3Hot and D3Cold handling for
 bridges

On Fri, Aug 02, 2024 at 12:53:42PM -0700, Hsin-Yi Wang wrote:

[...]

> > > [   42.202016] mt7921e 0000:01:00.0: PM: calling
> > > pci_pm_suspend_noirq+0x0/0x300 @ 77, parent: 0000:00:00.0
> > > [   42.231681] mt7921e 0000:01:00.0: PCI PM: Suspend power state: D3hot
> >
> > Here I can see that the port entered D3hot
> >
> This one is the wifi device connected to the port.
> 

Ah, okay. You could've just shared the logs for the bridge/rootport.

> > > [   42.238048] mt7921e 0000:01:00.0: PM:
> > > pci_pm_suspend_noirq+0x0/0x300 returned 0 after 26583 usecs
> > > [   42.247083] pcieport 0000:00:00.0: PM: calling
> > > pci_pm_suspend_noirq+0x0/0x300 @ 3196, parent: pci0000:00
> > > [   42.296325] pcieport 0000:00:00.0: PCI PM: Suspend power state: D0
> >
> This is the port suspended with D0. If we hack power_manageable to
> only consider D3hot, the state here for pcieport will become D3hot
> (compared in below).
> 
> If it's D0 (and s2idle), in resume it won't restore config:
> https://elixir.bootlin.com/linux/v6.10/source/drivers/pci/pci-driver.c#L959,
> and in resume it would be an issue.
> 
> Comparison:
> 1. pcieport can go to D3:
> (suspend)
> [   61.645809] mt7921e 0000:01:00.0: PM: calling
> pci_pm_suspend_noirq+0x0/0x2f8 @ 1139, parent: 0000:00:00.0
> [   61.675562] mt7921e 0000:01:00.0: PCI PM: Suspend power state: D3hot
> [   61.681931] mt7921e 0000:01:00.0: PM:
> pci_pm_suspend_noirq+0x0/0x2f8 returned 0 after 26502 usecs
> [   61.690959] pcieport 0000:00:00.0: PM: calling
> pci_pm_suspend_noirq+0x0/0x2f8 @ 3248, parent: pci0000:00
> [   61.755359] pcieport 0000:00:00.0: PCI PM: Suspend power state: D3hot
> [   61.761832] pcieport 0000:00:00.0: PM:
> pci_pm_suspend_noirq+0x0/0x2f8 returned 0 after 61345 usecs
> 

Why the device state is not saved? Did you skip those logs?

> (resume)
> [   65.243981] pcieport 0000:00:00.0: PM: calling
> pci_pm_resume_noirq+0x0/0x190 @ 3258, parent: pci0000:00
> [   65.253122] mtk-pcie-phy 16930000.phy: CKM_38=0x13040500,
> GLB_20=0x0, GLB_30=0x0, GLB_38=0x30453fc, GLB_F4=0x1453b000
> [   65.262725] pcieport 0000:00:00.0: PM:
> pci_pm_resume_noirq+0x0/0x190 returned 0 after 175 usecs
> [   65.273159] mtk-pcie-phy 16930000.phy: No calibration info
> [   65.281903] mt7921e 0000:01:00.0: PM: calling
> pci_pm_resume_noirq+0x0/0x190 @ 3259, parent: 0000:00:00.0
> [   65.297108] mt7921e 0000:01:00.0: PM: pci_pm_resume_noirq+0x0/0x190
> returned 0 after 329 usecs
> 
> 
> 2. pcieport stays at D0 due to power_manageable returns false:
> (suspend)
> [   52.435375] mt7921e 0000:01:00.0: PM: calling
> pci_pm_suspend_noirq+0x0/0x300 @ 2040, parent: 0000:00:00.0
> [   52.465235] mt7921e 0000:01:00.0: PCI PM: Suspend power state: D3hot
> [   52.471610] mt7921e 0000:01:00.0: PM:
> pci_pm_suspend_noirq+0x0/0x300 returned 0 after 26602 usecs
> [   52.480674] pcieport 0000:00:00.0: PM: calling
> pci_pm_suspend_noirq+0x0/0x300 @ 143, parent: pci0000:00
> [   52.529876] pcieport 0000:00:00.0: PCI PM: Suspend power state: D0
>                 <-- port is still D0
> [   52.536056] pcieport 0000:00:00.0: PCI PM: Skipped
> 
> (resume)
> [   56.026298] pcieport 0000:00:00.0: PM: calling
> pci_pm_resume_noirq+0x0/0x190 @ 3243, parent: pci0000:00
> [   56.035379] mtk-pcie-phy 16930000.phy: CKM_38=0x13040500,
> GLB_20=0x0, GLB_30=0x0, GLB_38=0x30453fc, GLB_F4=0x1453b000
> [   56.044776] pcieport 0000:00:00.0: PM:
> pci_pm_resume_noirq+0x0/0x190 returned 0 after 13 usecs
> [   56.055409] mtk-pcie-phy 16930000.phy: No calibration info
> [   56.064098] mt7921e 0000:01:00.0: PM: calling
> pci_pm_resume_noirq+0x0/0x190 @ 3244, parent: 0000:00:00.0
> [   56.078962] mt7921e 0000:01:00.0: Unable to change power state from
> D3hot to D0, device inaccessible                    <-- resume failed.

This means the port entered D3Cold? This is not expected during s2idle. During
s2idle, devices should be put into low power state and their power should be
preserved.

Who is pulling the plug here?

- Mani

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