linux-kernel - Re: [PATCH v4 3/5] PCI: Verify functions currently in D3cold have entered D0

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Message-ID: <561b6865-cba3-d640-b56d-072d06b94026@linux.intel.com>
Date: Fri, 23 Aug 2024 15:07:10 +0300 (EEST)
From: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
To: Mario Limonciello <superm1@...nel.org>
cc: Bjorn Helgaas <bhelgaas@...gle.com>, 
    Mathias Nyman <mathias.nyman@...el.com>, 
    Mika Westerberg <mika.westerberg@...ux.intel.com>, 
    "open list : PCI SUBSYSTEM" <linux-pci@...r.kernel.org>, 
    open list <linux-kernel@...r.kernel.org>, 
    "open list : USB XHCI DRIVER" <linux-usb@...r.kernel.org>, 
    Daniel Drake <drake@...lessos.org>, Gary Li <Gary.Li@....com>, 
    Greg Kroah-Hartman <gregkh@...uxfoundation.org>, 
    Mario Limonciello <mario.limonciello@....com>
Subject: Re: [PATCH v4 3/5] PCI: Verify functions currently in D3cold have
 entered D0

On Thu, 22 Aug 2024, Mario Limonciello wrote:

> From: Mario Limonciello <mario.limonciello@....com>
> 
> It is reported that USB4 routers and downstream devices may behave
> incorrectly if a dock cable is plugged in at approximately the time that
> the autosuspend_delay is configured. In this situation the device has
> attempted to enter D3cold, but didn't finish D3cold entry when the PCI
> core tried to transition it back to D0.
> 
> Empirically measuring this situation an "aborted" D3cold exit takes
> ~60ms and a "normal" D3cold exit takes ~6ms.
> 
> The PCI-PM 1.2 spec specifies that the restore time for functions
> in D3cold is either 'Full context restore or boot latency'.
> 
> As PCIe r6.0 sec 5.8 specifies that the device will have gone
> through a conventional reset, it may take some time for the
> device to be ready.
> 
> Wait up to 1 sec as specified in PCIe r6.0 sec 6.6.1 for a device
> in D3cold to return to D0.
> 
> Reviewed-by: Ilpo Järvinen <ilpo.jarvinen@...ux.intel.com>
> Signed-off-by: Mario Limonciello <mario.limonciello@....com>
> ---
>  drivers/pci/pci.c | 11 +++++++++++
>  drivers/pci/pci.h |  1 +
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/pci/pci.c b/drivers/pci/pci.c
> index b7717155e2fd0..7e861b6923d0a 100644
> --- a/drivers/pci/pci.c
> +++ b/drivers/pci/pci.c
> @@ -1425,6 +1425,17 @@ int pci_power_up(struct pci_dev *dev)
>  	else if (state == PCI_D2)
>  		udelay(PCI_PM_D2_DELAY);
>  
> +	/*
> +	 * D3cold -> D0 will have gone through a conventional reset and may need
> +	 * time to be ready.
> +	 */
> +	if (dev->current_state == PCI_D3cold) {
> +		int ret;
> +
> +		ret = pci_dev_wait(dev, PCI_DEV_WAIT_D3COLD_D0, PCI_RESET_WAIT);
> +		if (ret)
> +			return ret;
> +	}
>  end:
>  	dev->current_state = PCI_D0;
>  	if (need_restore)
> diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
> index 477257e843952..a675f5d55f298 100644
> --- a/drivers/pci/pci.h
> +++ b/drivers/pci/pci.h
> @@ -11,6 +11,7 @@ enum pci_reset_type {
>  	PCI_DEV_WAIT_BUS_RESET,
>  	PCI_DEV_WAIT_RESUME,
>  	PCI_DEV_WAIT_DPC,
> +	PCI_DEV_WAIT_D3COLD_D0,

Don't you need to add a string for this too? :-/

I wonder if it would be prudent to add PCI_DEV_WAIT_MAX and 
use static_assert() for the sizeof the pci_reset_types[] in patch 1 to 
autodetect mismatch (though it won't help if something is added in the 
middle of the list).

-- 
 i.