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Date: Wed, 27 Mar 2013 16:56:37 -0600
From: Bjorn Helgaas <bhelgaas@...gle.com>
To: Yinghai Lu <yinghai@...nel.org>
Cc: "Rafael J. Wysocki" <rjw@...k.pl>,
"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
"linux-acpi@...r.kernel.org" <linux-acpi@...r.kernel.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
Taku Izumi <izumi.taku@...fujitsu.com>,
Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>,
stable@...nel.org
Subject: Re: [PATCH] PCI: Remove not needed check in disable aspm link
On Mon, Mar 18, 2013 at 11:37 AM, Yinghai Lu <yinghai@...nel.org> wrote:
> Roman reported ath5k does not work anymore on 3.8.
> Bisected to
> | commit 8c33f51df406e1a1f7fa4e9b244845b7ebd61fa6
> | Author: Taku Izumi <izumi.taku@...fujitsu.com>
> | Date: Tue Oct 30 15:27:13 2012 +0900
> |
> | PCI/ACPI: Request _OSC control before scanning PCI root bus
> |
> | This patch moves up the code block to request _OSC control in order to
> | separate ACPI work and PCI work in acpi_pci_root_add().
>
> It make pci_disable_link_state does not work anymore as acpi_disabled
> is set before pci root bus scanning.
> It will skip that in quirks and pcie_aspm_sanity_check.
>
> We could revert to old logic, but that will make booting path and hotplug
> path with different aspm_disabled again.
>
> Acctually we don't need to check aspm_disabled in disable link, as
> we already have protection about link state following.
>
> https://bugzilla.kernel.org/show_bug.cgi?id=55211
> http://article.gmane.org/gmane.linux.kernel.pci/20640
>
> Need it for 3.8 stable.
>
> Reported-by: Roman Yepishev <roman.yepishev@...il.com>
> Bisected-by: Roman Yepishev <roman.yepishev@...il.com>
> Tested-by: Roman Yepishev <roman.yepishev@...il.com>
> Signed-off-by: Yinghai Lu <yinghai@...nel.org>
> Cc: Taku Izumi <izumi.taku@...fujitsu.com>
> Cc: Kenji Kaneshige <kaneshige.kenji@...fujitsu.com>
> Cc: stable@...nel.org
>
> ---
> drivers/pci/pcie/aspm.c | 21 ++++-----------------
> 1 file changed, 4 insertions(+), 17 deletions(-)
>
> Index: linux-2.6/drivers/pci/pcie/aspm.c
> ===================================================================
> --- linux-2.6.orig/drivers/pci/pcie/aspm.c
> +++ linux-2.6/drivers/pci/pcie/aspm.c
> @@ -493,15 +493,6 @@ static int pcie_aspm_sanity_check(struct
> return -EINVAL;
>
> /*
> - * If ASPM is disabled then we're not going to change
> - * the BIOS state. It's safe to continue even if it's a
> - * pre-1.1 device
> - */
> -
> - if (aspm_disabled)
> - continue;
> -
> - /*
> * Disable ASPM for pre-1.1 PCIe device, we follow MS to use
> * RBER bit to determine if a function is 1.1 version device
> */
> @@ -718,15 +709,11 @@ void pcie_aspm_powersave_config_link(str
> * pci_disable_link_state - disable pci device's link state, so the link will
> * never enter specific states
> */
> -static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem,
> - bool force)
> +static void __pci_disable_link_state(struct pci_dev *pdev, int state, bool sem)
> {
> struct pci_dev *parent = pdev->bus->self;
> struct pcie_link_state *link;
>
> - if (aspm_disabled && !force)
> - return;
> -
> if (!pci_is_pcie(pdev))
> return;
>
> @@ -757,13 +744,13 @@ static void __pci_disable_link_state(str
>
> void pci_disable_link_state_locked(struct pci_dev *pdev, int state)
> {
> - __pci_disable_link_state(pdev, state, false, false);
> + __pci_disable_link_state(pdev, state, false);
> }
> EXPORT_SYMBOL(pci_disable_link_state_locked);
>
> void pci_disable_link_state(struct pci_dev *pdev, int state)
> {
> - __pci_disable_link_state(pdev, state, true, false);
> + __pci_disable_link_state(pdev, state, true);
> }
> EXPORT_SYMBOL(pci_disable_link_state);
>
> @@ -781,7 +768,7 @@ void pcie_clear_aspm(struct pci_bus *bus
> __pci_disable_link_state(child, PCIE_LINK_STATE_L0S |
> PCIE_LINK_STATE_L1 |
> PCIE_LINK_STATE_CLKPM,
> - false, true);
> + false);
> }
> }
>
This might fix the problem, but the code is still a mess. In
acpi_pci_root_add(), why do we have the following?
acpi_pci_root_add
acpi_pci_osc_support
if (flags != base_flags)
pcie_no_aspm
if (...)
acpi_pci_osc_control_set
if (ACPI_SUCCESS)
is_osc_granted = true
pci_acpi_scan_root
if (is_osc_granted)
if (acpi_gbl_FADT.boot_flags & ACPI_FADT_NO_ASPM)
pcie_clear_aspm
else
pcie_no_aspm
Why can't we set all the ASPM flags *first*, before calling
pci_acpi_scan_root()? That way we could just do the correct ASPM
setup as we discover devices during enumeration, rather than trying to
fix things up afterwards. I suspect pcie_clear_aspm() is broken
anyway, because it looks like it only touches one level of the
hierarchy, without recursively descending it.
But Taku went to some trouble in 8c33f51d to introduce is_osc_granted
to remember this until after pci_acpi_scan_root(), so presumably
there's some reason for this. Do you remember why, Taku?
Bjorn
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