linux-kernel - Re: [PATCH] ACPI: Fix osc flag setup ordering to allow pcie hotplug use when available

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Message-ID: <2074111.WRY7FfU4Ni@vostro.rjw.lan>
Date:	Fri, 23 Aug 2013 21:38:18 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Neil Horman <nhorman@...driver.com>
Cc:	linux-kernel@...r.kernel.org, Len Brown <lenb@...nel.org>,
	linux-acpi@...r.kernel.org, Bjorn Helgaas <bhelgaas@...gle.com>,
	Yinghai Lu <yinghai@...nel.org>,
	Linux PCI <linux-pci@...r.kernel.org>
Subject: Re: [PATCH] ACPI: Fix osc flag setup ordering to allow pcie hotplug use when available

[CCs added]

Please always send PCI-related material to linux-pci in the first place.

The change that broke things for you was actually intentional:

commit b8178f130e25c1bdac1c33e0996f1ff6e20ec08e
Author: Bjorn Helgaas <bhelgaas@...gle.com>
Date:   Mon Apr 1 15:47:39 2013 -0600

    Revert "PCI/ACPI: Request _OSC control before scanning PCI root bus"
    
    This reverts commit 8c33f51df406e1a1f7fa4e9b244845b7ebd61fa6.

so I think we'll need to clean up the ASMP initialization after all.

On Friday, August 23, 2013 01:19:39 PM Neil Horman wrote:
> Somewhere between 3.9 and 3.10 it seems the order in which pcie and acpi probed
> slots for hotplug capabilites got reversed.  While this isn't a big deal, it did
> uncover a bug in the ACPI bus setup path.  Specifically, acpi_pci_root_add calls
> pci_acpi_scan_root before setting the osc flags for the device handle.
> pci_acpi_scan_root, among other things uses device_is_managed_by_native_pciehp()
> to determine if a given slot has pcie hotplug capabilties, whcih checks the
> devices OSC_PCI_EXPRESS_NATIVE_HP_CONTROL flag.  Since that flag is not set
> until after pci_acpi_scan_root_completes, the acpi code never sees that pcie
> slots are hotplug capable and configures them all to use acpi instead.
> 
> Fix is pretty simple, just defer the scan until after the osc flags have been
> set on the device.  Tested by myself and it seems to work well.
> 
> Signed-off-by: Neil Horman <nhorman@...driver.com>
> CC: Len Brown <lenb@...nel.org>
> CC: "Rafael J. Wysocki" <rjw@...k.pl>
> CC: linux-acpi@...r.kernel.org
> ---
>  drivers/acpi/pci_root.c | 41 ++++++++++++++++++++---------------------
>  1 file changed, 20 insertions(+), 21 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 5917839..a2c2661 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -437,27 +437,6 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  	flags = base_flags = OSC_PCI_SEGMENT_GROUPS_SUPPORT;
>  	acpi_pci_osc_support(root, flags);
>  
> -	/*
> -	 * TBD: Need PCI interface for enumeration/configuration of roots.
> -	 */
> -
> -	/*
> -	 * Scan the Root Bridge
> -	 * --------------------
> -	 * Must do this prior to any attempt to bind the root device, as the
> -	 * PCI namespace does not get created until this call is made (and
> -	 * thus the root bridge's pci_dev does not exist).
> -	 */
> -	root->bus = pci_acpi_scan_root(root);
> -	if (!root->bus) {
> -		dev_err(&device->dev,
> -			"Bus %04x:%02x not present in PCI namespace\n",
> -			root->segment, (unsigned int)root->secondary.start);
> -		result = -ENODEV;
> -		goto end;
> -	}
> -
> -	/* Indicate support for various _OSC capabilities. */
>  	if (pci_ext_cfg_avail())
>  		flags |= OSC_EXT_PCI_CONFIG_SUPPORT;
>  	if (pcie_aspm_support_enabled()) {
> @@ -520,6 +499,26 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  			 "(_OSC support mask: 0x%02x)\n", flags);
>  	}
>  
> +	/*
> +	 * TBD: Need PCI interface for enumeration/configuration of roots.
> +	 */
> +
> +	/*
> +	 * Scan the Root Bridge
> +	 * --------------------
> +	 * Must do this prior to any attempt to bind the root device, as the
> +	 * PCI namespace does not get created until this call is made (and
> +	 * thus the root bridge's pci_dev does not exist).
> +	 */
> +	root->bus = pci_acpi_scan_root(root);
> +	if (!root->bus) {
> +		dev_err(&device->dev,
> +			"Bus %04x:%02x not present in PCI namespace\n",
> +			root->segment, (unsigned int)root->secondary.start);
> +		result = -ENODEV;
> +		goto end;
> +	}
> +
>  	pci_acpi_add_bus_pm_notifier(device, root->bus);
>  	if (device->wakeup.flags.run_wake)
>  		device_set_run_wake(root->bus->bridge, true);
> 
-- 
I speak only for myself.
Rafael J. Wysocki, Intel Open Source Technology Center.
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