Re: [PATCH v4] ACPI: Fix osc flag setup ordering to allow pciehotplug use when available

[Bjorn Helgaas]

On Thu, Aug 29, 2013 at 04:17:05PM -0400, Neil Horman wrote:
> This is a fix for:
> https://bugzilla.kernel.org/show_bug.cgi?id=60736
> 
> During the 3.8 devel cycle:
> 
> commit 8c33f51df406e1a1f7fa4e9b244845b7ebd61fa6
> Author: Taku Izumi <izumi.taku@xxxxxxxxxxxxxx>
> Date:   Tue Oct 30 15:27:13 2012 +0900
> 
>     PCI/ACPI: Request _OSC control before scanning PCI root bus
> 
> went in to allow us to query the pcie hotplug flags during the acpi bus scan.
> It however caused problems with the disabling of pcie aspm, and so:
> commit b8178f130e25c1bdac1c33e0996f1ff6e20ec08e
> Author: Bjorn Helgaas <bhelgaas@xxxxxxxxxx>
> Date:   Mon Apr 1 15:47:39 2013 -0600
> 
>     Revert "PCI/ACPI: Request _OSC control before scanning PCI root bus"
> 
> Backed it out.  This of course brought back the problem in which acpi took over
> hotplug ports that were meant to be controlled by pcie.
> 
> This patch gives us both items.  It lets us request _OSC control before scanning
> the pci root bus, but defers any disabling of aspm until after the scan is
> complete, allowing us to properly handle old pcie 1.1 devices aspm settings
> properly, as b8178f130e documents.
> 
> Tested successfully by myself.
> 
> Signed-off-by: Neil Horman <nhorman@xxxxxxxxxxxxx>
> CC: Len Brown <lenb@xxxxxxxxxx>
> CC: "Rafael J. Wysocki" <rjw@xxxxxxx>
> CC: linux-acpi@xxxxxxxxxxxxxxx
> CC: linux-pci@xxxxxxxxxxxxxxx

I added Yinghai's ack and a stable tag and put this in pci/misc
for v3.12.  Thanks!

I reworked the changelog because I think the actual cause of the
regression was 3b63aaa70e, not the _OSC commits you mentioned:

8c33f51df4 ("PCI/ACPI: Request _OSC control before scanning PCI root bus")
appeared in v3.8 and broke ASPM but not acpiphp.

b8178f130e ('Revert "PCI/ACPI: Request _OSC control before scanning PCI
root bus"') appeared in v3.9 and fixed ASPM, leaving acpiphp working.

3b63aaa70e ("PCI: acpiphp: Do not use ACPI PCI subdriver mechanism")
appeared in v3.10, and I believe this is what actually broke acpiphp
because it moved the acpiphp initialization earlier, into the bus scan.

in v3.8:
    acpi_pci_root_add
      acpi_pci_osc_control_set          # request OS control
      pci_acpi_scan_root                # scan bus
    acpi_pci_root_start
      add_bridge                        # acpi_pci_driver .add method
        ...
          device_is_managed_by_native_pciehp	# OK

in v3.9:
    acpi_pci_root_add
      pci_acpi_scan_root                # scan bus
      acpi_pci_osc_control_set          # request OS control
      add_bridge                        # acpi_pci_driver .add method
        ...
          device_is_managed_by_native_pciehp	# OK

in v3.10:
    acpi_pci_root_add
      pci_acpi_scan_root                # scan bus
        ...
          acpiphp_enumerate_slots
            ...
              device_is_managed_by_native_pciehp	# PROBLEM
      acpi_pci_osc_control_set          # request OS control

So I added a stable tag for v3.10+ only.  I'll ask Linus to merge it
directly during the merge window for v3.12, and hopefully it will be
backported to the v3.10 and v3.11 stable trees soon after that.

Bjorn

> ---
>  drivers/acpi/pci_root.c | 62 ++++++++++++++++++++++++++++++-------------------
>  1 file changed, 38 insertions(+), 24 deletions(-)
> 
> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
> index 5917839..6110fd2 100644
> --- a/drivers/acpi/pci_root.c
> +++ b/drivers/acpi/pci_root.c
> @@ -378,6 +378,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  	struct acpi_pci_root *root;
>  	u32 flags, base_flags;
>  	acpi_handle handle = device->handle;
> +	bool no_aspm = false, clear_aspm = false;
>  
>  	root = kzalloc(sizeof(struct acpi_pci_root), GFP_KERNEL);
>  	if (!root)
> @@ -437,27 +438,6 @@ 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()) {
> @@ -471,7 +451,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  		if (ACPI_FAILURE(status)) {
>  			dev_info(&device->dev, "ACPI _OSC support "
>  				"notification failed, disabling PCIe ASPM\n");
> -			pcie_no_aspm();
> +			no_aspm = true;
>  			flags = base_flags;
>  		}
>  	}
> @@ -503,7 +483,7 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  				 * We have ASPM control, but the FADT indicates
>  				 * that it's unsupported. Clear it.
>  				 */
> -				pcie_clear_aspm(root->bus);
> +				clear_aspm = true;
>  			}
>  		} else {
>  			dev_info(&device->dev,
> @@ -512,7 +492,14 @@ static int acpi_pci_root_add(struct acpi_device *device,
>  				acpi_format_exception(status), flags);
>  			dev_info(&device->dev,
>  				 "ACPI _OSC control for PCIe not granted, disabling ASPM\n");
> -			pcie_no_aspm();
> +			/*
> +			 * We want to disable aspm here, but aspm_disabled 
> +			 * needs to remain in its state from boot so that we
> +			 * properly handle pcie 1.1 devices.  So we set this
> +			 * flag here, to defer the action until after the acpi
> +			 * root scan
> +			 */
> +			no_aspm = true;
>  		}
>  	} else {
>  		dev_info(&device->dev,
> @@ -520,6 +507,33 @@ 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;
> +	}
> +
> +	if (clear_aspm) {
> +		dev_info(&device->dev, "Disabling ASPM (FADT indicates it is unsupported)\n");
> +		pcie_clear_aspm(root->bus);
> +	}
> +	if (no_aspm)
> +		pcie_no_aspm();
> +
>  	pci_acpi_add_bus_pm_notifier(device, root->bus);
>  	if (device->wakeup.flags.run_wake)
>  		device_set_run_wake(root->bus->bridge, true);
> -- 
> 1.8.1.4
> 
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