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SubjectRe: [PATCH 1/2] PCI: ASPM exit link state code could skip devices
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On Fri, 2013-01-18 at 13:23 -0500, Joe Lawrence wrote:
> From 3a51bbad5555ba6c6e144aa5176c8112eb449325 Mon Sep 17 00:00:00 2001
> From: Joe Lawrence <joe.lawrence@stratus.com>
> Date: Tue, 15 Jan 2013 14:51:57 -0500
> Subject: [PATCH 1/2] PCI: ASPM exit link state code could skip devices
>
> On PCI bus hotplug removal, pcie_aspm_exit_link_state could potentially skip
> parent devices that have link_state allocated. Instead of exiting early if
> a given device is not PCIe, check that the device's parent is PCIe. This
> enables pcie_aspm_exit_link_state to properly clean up parent link_state when
> the last function in a slot might not be PCIe.
>
> Reviewed-by: David Bulkow <david.bulkow@stratus.com>
> Signed-off-by: Joe Lawrence <joe.lawrence@stratus.com>
> ---
> drivers/pci/pcie/aspm.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index b52630b..6122447 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -634,7 +634,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
> struct pci_dev *parent = pdev->bus->self;
> struct pcie_link_state *link, *root, *parent_link;
>
> - if (!pci_is_pcie(pdev) || !parent || !parent->link_state)
> + if (!parent || !pci_is_pcie(parent) || !parent->link_state)
> return;
> if ((pci_pcie_type(parent) != PCI_EXP_TYPE_ROOT_PORT) &&
> (pci_pcie_type(parent) != PCI_EXP_TYPE_DOWNSTREAM))

Joe:

Bjorn and I looked at this again today and think the checks that occur
early in 'pcie_aspm_exit_link_state()' could be simplified (as shown
below) to avoid issues such as you are encountering.

I think part of the confusion concerning the asymmetry between
'pcie_aspm_init_link_state()' and 'pcie_aspm_exit_link_state()' is that
the former is passed in a pointer to a bridge device whereas the latter
is passed in a pointer to a end-point device. Frankly, I find the
entire driver to be confusing and very hard to understand.

Could you please test with the following patch and let us know the
results?


PCI: ASPM exit link state code is skipping devices

From: Myron Stowe <myron.stowe@redhat.com>

On PCI bus hotplug removal, 'pcie_aspm_exit_link_state' can potentially
skip parent devices that have link_state allocated. Instead of exiting
early if a given device in not PCIe, check whether or not the device's
parent has link_state allocated. This enables 'pcie_aspm_exit_link_state'
to properly clean up parent link_state when the last function in a slot
might not be PCIe.

Reported-by: Joe Lawrence <joe.lawrence@stratus.com>
Signed-off-by: Myron Stowe <myron.stowe@redhat.com>
---

drivers/pci/pcie/aspm.c | 5 +----
1 files changed, 1 insertions(+), 4 deletions(-)


diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 8474b6a..aa52727 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -634,10 +634,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
struct pci_dev *parent = pdev->bus->self;
struct pcie_link_state *link, *root, *parent_link;

- if (!pci_is_pcie(pdev) || !parent || !parent->link_state)
- return;
- if ((pci_pcie_type(parent) != PCI_EXP_TYPE_ROOT_PORT) &&
- (pci_pcie_type(parent) != PCI_EXP_TYPE_DOWNSTREAM))
+ if (!parent || !parent->link_state)
return;

down_read(&pci_bus_sem);



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