Patchwork [1/3] pci: Add PCI walk function and PCIe bridge test

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Submitter Alex Williamson
Date May 10, 2013, 9:18 p.m.
Message ID <20130510211845.32592.77464.stgit@bling.home>
Download mbox | patch
Permalink /patch/243068/
State Not Applicable
Headers show

Comments

Alex Williamson - May 10, 2013, 9:18 p.m.
These will replace pci_find_upstream_pcie_bridge, which is difficult
to use and rather specific to intel-iommu usage.  A quirked
pci_is_pcie_bridge function is provided to work around non-compliant
PCIe-to-PCI bridges such as those found in
https://bugzilla.kernel.org/show_bug.cgi?id=44881

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---
 drivers/pci/search.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/pci.h  |   23 ++++++++++++++++++++
 2 files changed, 80 insertions(+)


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Sethi Varun-B16395 - May 13, 2013, 1:51 p.m.
Would these functions be used outside drivers/iommu? We recently added pci.h under drivers/iommu, maybe we can add a new file for these functions as well.

-Varun
> -----Original Message-----
> From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
> bounces@lists.linux-foundation.org] On Behalf Of Alex Williamson
> Sent: Saturday, May 11, 2013 2:49 AM
> To: bhelgaas@google.com; stephen@networkplumber.org
> Cc: linux-pci@vger.kernel.org; iommu@lists.linux-foundation.org;
> dwmw2@infradead.org
> Subject: [PATCH 1/3] pci: Add PCI walk function and PCIe bridge test
> 
> These will replace pci_find_upstream_pcie_bridge, which is difficult to
> use and rather specific to intel-iommu usage.  A quirked
> pci_is_pcie_bridge function is provided to work around non-compliant
> PCIe-to-PCI bridges such as those found in
> https://bugzilla.kernel.org/show_bug.cgi?id=44881
> 
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/pci/search.c |   57
> ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h  |   23 ++++++++++++++++++++
>  2 files changed, 80 insertions(+)
> 
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c index
> d0627fa..0357f74 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -17,6 +17,63 @@
>  DECLARE_RWSEM(pci_bus_sem);
>  EXPORT_SYMBOL_GPL(pci_bus_sem);
> 
> +/* Test for PCIe bridges. */
> +bool pci_is_pcie_bridge(struct pci_dev *pdev) {
> +	if (!pci_is_bridge(pdev))
> +		return false;
> +
> +	if (pci_is_pcie(pdev))
> +		return true;
> +
> +#ifdef CONFIG_PCI_QUIRKS
> +	/*
> +	 * If we're not on the root bus, look one device upstream of the
> +	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
> +	 * bridge, then the current device is effectively PCIe as it must
> +	 * be the PCIe-to-PCI bridge.  This handles several bridges that
> +	 * violate the PCIe spec by not exposing a PCIe capability:
> +	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
> +	 */
> +	if (!pci_is_root_bus(pdev->bus)) {
> +		struct pci_dev *parent = pdev->bus->self;
> +
> +		if (pci_is_pcie(parent) &&
> +		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> +
> +			return true;
> +	}
> +#endif
> +	return false;
> +}
> +
> +/*
> + * Walk upstream from the given pdev for the first device returning
> + * true for the provided match function.  If no match is found, return
> + * NULL.  *last records the previous step in the walk.
> + */
> +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> +					   bool (*match)(struct pci_dev *),
> +					   struct pci_dev **last)
> +{
> +	*last = NULL;
> +
> +	if (match(pdev))
> +		return pdev;
> +
> +	*last = pdev;
> +
> +	while (!pci_is_root_bus(pdev->bus)) {
> +		*last = pdev;
> +		pdev = pdev->bus->self;
> +
> +		if (match(pdev))
> +			return pdev;
> +	}
> +
> +	return NULL;
> +}
> +
>  /*
>   * find the upstream PCIe-to-PCI bridge of a PCI device
>   * if the device is PCIE, return NULL
> diff --git a/include/linux/pci.h b/include/linux/pci.h index
> bd8ec30..e87423a 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1855,6 +1855,29 @@ static inline struct eeh_dev
> *pci_dev_to_eeh_dev(struct pci_dev *pdev)  #endif
> 
>  /**
> + * pci_walk_up_to_first_match - Generic upstream search function
> + * @pdev: starting PCI device to search
> + * @match: match function to call on each device (true = match)
> + * @last: last device examined prior to returned device
> + *
> + * Walk upstream from the given device, calling match() at each device.
> + * Returns the first device matching match().  If the root bus is
> +reached
> + * without finding a match, return NULL.  last returns the N-1 step in
> + * the search path.
> + */
> +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> +					   bool (*match)(struct pci_dev *),
> +					   struct pci_dev **last);
> +
> +/**
> + * pci_is_pcie_bridge - Match a PCIe bridge device
> + * @pdev: device to test
> + *
> + * Return true if the given device is a PCIe bridge, false otherwise.
> + */
> +bool pci_is_pcie_bridge(struct pci_dev *pdev);
> +
> +/**
>   * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a
> device
>   * @pdev: the PCI device
>   *
> 
> _______________________________________________
> iommu mailing list
> iommu@lists.linux-foundation.org
> https://lists.linuxfoundation.org/mailman/listinfo/iommu


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Alex Williamson - May 13, 2013, 2:49 p.m.
On Mon, 2013-05-13 at 13:51 +0000, Sethi Varun-B16395 wrote:
> Would these functions be used outside drivers/iommu? We recently added pci.h under drivers/iommu, maybe we can add a new file for these functions as well.

The intention is to make them generic enough for pci-core, unlike
pci_find_upstream_pcie_bridge, which was rather specific to iommu usage.
Thanks,

Alex

> > -----Original Message-----
> > From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
> > bounces@lists.linux-foundation.org] On Behalf Of Alex Williamson
> > Sent: Saturday, May 11, 2013 2:49 AM
> > To: bhelgaas@google.com; stephen@networkplumber.org
> > Cc: linux-pci@vger.kernel.org; iommu@lists.linux-foundation.org;
> > dwmw2@infradead.org
> > Subject: [PATCH 1/3] pci: Add PCI walk function and PCIe bridge test
> > 
> > These will replace pci_find_upstream_pcie_bridge, which is difficult to
> > use and rather specific to intel-iommu usage.  A quirked
> > pci_is_pcie_bridge function is provided to work around non-compliant
> > PCIe-to-PCI bridges such as those found in
> > https://bugzilla.kernel.org/show_bug.cgi?id=44881
> > 
> > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > ---
> >  drivers/pci/search.c |   57
> > ++++++++++++++++++++++++++++++++++++++++++++++++++
> >  include/linux/pci.h  |   23 ++++++++++++++++++++
> >  2 files changed, 80 insertions(+)
> > 
> > diff --git a/drivers/pci/search.c b/drivers/pci/search.c index
> > d0627fa..0357f74 100644
> > --- a/drivers/pci/search.c
> > +++ b/drivers/pci/search.c
> > @@ -17,6 +17,63 @@
> >  DECLARE_RWSEM(pci_bus_sem);
> >  EXPORT_SYMBOL_GPL(pci_bus_sem);
> > 
> > +/* Test for PCIe bridges. */
> > +bool pci_is_pcie_bridge(struct pci_dev *pdev) {
> > +	if (!pci_is_bridge(pdev))
> > +		return false;
> > +
> > +	if (pci_is_pcie(pdev))
> > +		return true;
> > +
> > +#ifdef CONFIG_PCI_QUIRKS
> > +	/*
> > +	 * If we're not on the root bus, look one device upstream of the
> > +	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
> > +	 * bridge, then the current device is effectively PCIe as it must
> > +	 * be the PCIe-to-PCI bridge.  This handles several bridges that
> > +	 * violate the PCIe spec by not exposing a PCIe capability:
> > +	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
> > +	 */
> > +	if (!pci_is_root_bus(pdev->bus)) {
> > +		struct pci_dev *parent = pdev->bus->self;
> > +
> > +		if (pci_is_pcie(parent) &&
> > +		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> > +
> > +			return true;
> > +	}
> > +#endif
> > +	return false;
> > +}
> > +
> > +/*
> > + * Walk upstream from the given pdev for the first device returning
> > + * true for the provided match function.  If no match is found, return
> > + * NULL.  *last records the previous step in the walk.
> > + */
> > +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> > +					   bool (*match)(struct pci_dev *),
> > +					   struct pci_dev **last)
> > +{
> > +	*last = NULL;
> > +
> > +	if (match(pdev))
> > +		return pdev;
> > +
> > +	*last = pdev;
> > +
> > +	while (!pci_is_root_bus(pdev->bus)) {
> > +		*last = pdev;
> > +		pdev = pdev->bus->self;
> > +
> > +		if (match(pdev))
> > +			return pdev;
> > +	}
> > +
> > +	return NULL;
> > +}
> > +
> >  /*
> >   * find the upstream PCIe-to-PCI bridge of a PCI device
> >   * if the device is PCIE, return NULL
> > diff --git a/include/linux/pci.h b/include/linux/pci.h index
> > bd8ec30..e87423a 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -1855,6 +1855,29 @@ static inline struct eeh_dev
> > *pci_dev_to_eeh_dev(struct pci_dev *pdev)  #endif
> > 
> >  /**
> > + * pci_walk_up_to_first_match - Generic upstream search function
> > + * @pdev: starting PCI device to search
> > + * @match: match function to call on each device (true = match)
> > + * @last: last device examined prior to returned device
> > + *
> > + * Walk upstream from the given device, calling match() at each device.
> > + * Returns the first device matching match().  If the root bus is
> > +reached
> > + * without finding a match, return NULL.  last returns the N-1 step in
> > + * the search path.
> > + */
> > +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> > +					   bool (*match)(struct pci_dev *),
> > +					   struct pci_dev **last);
> > +
> > +/**
> > + * pci_is_pcie_bridge - Match a PCIe bridge device
> > + * @pdev: device to test
> > + *
> > + * Return true if the given device is a PCIe bridge, false otherwise.
> > + */
> > +bool pci_is_pcie_bridge(struct pci_dev *pdev);
> > +
> > +/**
> >   * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a
> > device
> >   * @pdev: the PCI device
> >   *
> > 
> > _______________________________________________
> > iommu mailing list
> > iommu@lists.linux-foundation.org
> > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> 
> 



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Sethi Varun-B16395 - May 22, 2013, 2:34 p.m.
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Alex Williamson - May 22, 2013, 3:02 p.m.
On Wed, 2013-05-22 at 14:34 +0000, Sethi Varun-B16395 wrote:
> Any idea when would this patch set be integrated? Freescale PAMU
> driver depends on this patch. Currently I am using the
> pci_find_pcie_upstream_bridge routine in the device group creation
> routine.

I don't know, Bjorn?  The bugzilla referenced in patch 0/3 has several
reports from users that this series solves the problem for them.
Thanks,

Alex

> > -----Original Message-----
> > From: Alex Williamson [mailto:alex.williamson@redhat.com]
> > Sent: Monday, May 13, 2013 8:19 PM
> > To: Sethi Varun-B16395
> > Cc: bhelgaas@google.com; stephen@networkplumber.org; linux-
> > pci@vger.kernel.org; iommu@lists.linux-foundation.org;
> > dwmw2@infradead.org
> > Subject: Re: [PATCH 1/3] pci: Add PCI walk function and PCIe bridge test
> > 
> > On Mon, 2013-05-13 at 13:51 +0000, Sethi Varun-B16395 wrote:
> > > Would these functions be used outside drivers/iommu? We recently added
> > pci.h under drivers/iommu, maybe we can add a new file for these
> > functions as well.
> > 
> > The intention is to make them generic enough for pci-core, unlike
> > pci_find_upstream_pcie_bridge, which was rather specific to iommu usage.
> > Thanks,
> > 
> > Alex
> > 
> > > > -----Original Message-----
> > > > From: iommu-bounces@lists.linux-foundation.org [mailto:iommu-
> > > > bounces@lists.linux-foundation.org] On Behalf Of Alex Williamson
> > > > Sent: Saturday, May 11, 2013 2:49 AM
> > > > To: bhelgaas@google.com; stephen@networkplumber.org
> > > > Cc: linux-pci@vger.kernel.org; iommu@lists.linux-foundation.org;
> > > > dwmw2@infradead.org
> > > > Subject: [PATCH 1/3] pci: Add PCI walk function and PCIe bridge test
> > > >
> > > > These will replace pci_find_upstream_pcie_bridge, which is difficult
> > > > to use and rather specific to intel-iommu usage.  A quirked
> > > > pci_is_pcie_bridge function is provided to work around non-compliant
> > > > PCIe-to-PCI bridges such as those found in
> > > > https://bugzilla.kernel.org/show_bug.cgi?id=44881
> > > >
> > > > Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> > > > ---
> > > >  drivers/pci/search.c |   57
> > > > ++++++++++++++++++++++++++++++++++++++++++++++++++
> > > >  include/linux/pci.h  |   23 ++++++++++++++++++++
> > > >  2 files changed, 80 insertions(+)
> > > >
> > > > diff --git a/drivers/pci/search.c b/drivers/pci/search.c index
> > > > d0627fa..0357f74 100644
> > > > --- a/drivers/pci/search.c
> > > > +++ b/drivers/pci/search.c
> > > > @@ -17,6 +17,63 @@
> > > >  DECLARE_RWSEM(pci_bus_sem);
> > > >  EXPORT_SYMBOL_GPL(pci_bus_sem);
> > > >
> > > > +/* Test for PCIe bridges. */
> > > > +bool pci_is_pcie_bridge(struct pci_dev *pdev) {
> > > > +	if (!pci_is_bridge(pdev))
> > > > +		return false;
> > > > +
> > > > +	if (pci_is_pcie(pdev))
> > > > +		return true;
> > > > +
> > > > +#ifdef CONFIG_PCI_QUIRKS
> > > > +	/*
> > > > +	 * If we're not on the root bus, look one device upstream of the
> > > > +	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
> > > > +	 * bridge, then the current device is effectively PCIe as it must
> > > > +	 * be the PCIe-to-PCI bridge.  This handles several bridges that
> > > > +	 * violate the PCIe spec by not exposing a PCIe capability:
> > > > +	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
> > > > +	 */
> > > > +	if (!pci_is_root_bus(pdev->bus)) {
> > > > +		struct pci_dev *parent = pdev->bus->self;
> > > > +
> > > > +		if (pci_is_pcie(parent) &&
> > > > +		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> > > > +
> > > > +			return true;
> > > > +	}
> > > > +#endif
> > > > +	return false;
> > > > +}
> > > > +
> > > > +/*
> > > > + * Walk upstream from the given pdev for the first device returning
> > > > + * true for the provided match function.  If no match is found,
> > > > +return
> > > > + * NULL.  *last records the previous step in the walk.
> > > > + */
> > > > +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> > > > +					   bool (*match)(struct pci_dev *),
> > > > +					   struct pci_dev **last)
> > > > +{
> > > > +	*last = NULL;
> > > > +
> > > > +	if (match(pdev))
> > > > +		return pdev;
> > > > +
> > > > +	*last = pdev;
> > > > +
> > > > +	while (!pci_is_root_bus(pdev->bus)) {
> > > > +		*last = pdev;
> > > > +		pdev = pdev->bus->self;
> > > > +
> > > > +		if (match(pdev))
> > > > +			return pdev;
> > > > +	}
> > > > +
> > > > +	return NULL;
> > > > +}
> > > > +
> > > >  /*
> > > >   * find the upstream PCIe-to-PCI bridge of a PCI device
> > > >   * if the device is PCIE, return NULL diff --git
> > > > a/include/linux/pci.h b/include/linux/pci.h index bd8ec30..e87423a
> > > > 100644
> > > > --- a/include/linux/pci.h
> > > > +++ b/include/linux/pci.h
> > > > @@ -1855,6 +1855,29 @@ static inline struct eeh_dev
> > > > *pci_dev_to_eeh_dev(struct pci_dev *pdev)  #endif
> > > >
> > > >  /**
> > > > + * pci_walk_up_to_first_match - Generic upstream search function
> > > > + * @pdev: starting PCI device to search
> > > > + * @match: match function to call on each device (true = match)
> > > > + * @last: last device examined prior to returned device
> > > > + *
> > > > + * Walk upstream from the given device, calling match() at each
> > device.
> > > > + * Returns the first device matching match().  If the root bus is
> > > > +reached
> > > > + * without finding a match, return NULL.  last returns the N-1 step
> > > > +in
> > > > + * the search path.
> > > > + */
> > > > +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> > > > +					   bool (*match)(struct pci_dev *),
> > > > +					   struct pci_dev **last);
> > > > +
> > > > +/**
> > > > + * pci_is_pcie_bridge - Match a PCIe bridge device
> > > > + * @pdev: device to test
> > > > + *
> > > > + * Return true if the given device is a PCIe bridge, false
> > otherwise.
> > > > + */
> > > > +bool pci_is_pcie_bridge(struct pci_dev *pdev);
> > > > +
> > > > +/**
> > > >   * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge
> > > > of a device
> > > >   * @pdev: the PCI device
> > > >   *
> > > >
> > > > _______________________________________________
> > > > iommu mailing list
> > > > iommu@lists.linux-foundation.org
> > > > https://lists.linuxfoundation.org/mailman/listinfo/iommu
> > >
> > >
> > 
> > 
> > 
> 



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Bjorn Helgaas - May 23, 2013, 8:44 p.m.
On Fri, May 10, 2013 at 3:18 PM, Alex Williamson
<alex.williamson@redhat.com> wrote:
> These will replace pci_find_upstream_pcie_bridge, which is difficult
> to use and rather specific to intel-iommu usage.  A quirked
> pci_is_pcie_bridge function is provided to work around non-compliant
> PCIe-to-PCI bridges such as those found in
> https://bugzilla.kernel.org/show_bug.cgi?id=44881
>
> Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
> ---
>  drivers/pci/search.c |   57 ++++++++++++++++++++++++++++++++++++++++++++++++++
>  include/linux/pci.h  |   23 ++++++++++++++++++++
>  2 files changed, 80 insertions(+)
>
> diff --git a/drivers/pci/search.c b/drivers/pci/search.c
> index d0627fa..0357f74 100644
> --- a/drivers/pci/search.c
> +++ b/drivers/pci/search.c
> @@ -17,6 +17,63 @@
>  DECLARE_RWSEM(pci_bus_sem);
>  EXPORT_SYMBOL_GPL(pci_bus_sem);
>
> +/* Test for PCIe bridges. */
> +bool pci_is_pcie_bridge(struct pci_dev *pdev)
> +{
> +       if (!pci_is_bridge(pdev))
> +               return false;
> +
> +       if (pci_is_pcie(pdev))
> +               return true;
> +
> +#ifdef CONFIG_PCI_QUIRKS
> +       /*
> +        * If we're not on the root bus, look one device upstream of the
> +        * current device.  If that device is PCIe and is not a PCIe-to-PCI
> +        * bridge, then the current device is effectively PCIe as it must
> +        * be the PCIe-to-PCI bridge.  This handles several bridges that
> +        * violate the PCIe spec by not exposing a PCIe capability:
> +        * https://bugzilla.kernel.org/show_bug.cgi?id=44881
> +        */
> +       if (!pci_is_root_bus(pdev->bus)) {
> +               struct pci_dev *parent = pdev->bus->self;
> +
> +               if (pci_is_pcie(parent) &&
> +                   pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
> +
> +                       return true;
> +       }
> +#endif
> +       return false;
> +}

I like this strategy.  But I'd rather it not be a general-purpose PCI
interface, because if pci_is_pcie_bridge() is true, people will assume
they can perform PCIe operations on the device, and they can't.  The
only use for this is to figure out the source ID the IOMMU will see,
so I think this should just go in the IOMMU code.

> +/*
> + * Walk upstream from the given pdev for the first device returning
> + * true for the provided match function.  If no match is found, return
> + * NULL.  *last records the previous step in the walk.
> + */
> +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> +                                          bool (*match)(struct pci_dev *),
> +                                          struct pci_dev **last)
> +{
> +       *last = NULL;
> +
> +       if (match(pdev))
> +               return pdev;
> +
> +       *last = pdev;
> +
> +       while (!pci_is_root_bus(pdev->bus)) {
> +               *last = pdev;
> +               pdev = pdev->bus->self;
> +
> +               if (match(pdev))
> +                       return pdev;
> +       }
> +
> +       return NULL;
> +}

Same here.  I don't really see much potential for other uses of this,
so it seems like you might as well just put this in the IOMMU code and
make it call pci_is_pcie_bridge() directly.

The "source ID == upstream PCIe bridge" mapping is deeply ingrained in
your skull, but I think it would make the intent of the code clearer
if the function names mentioned the source ID somehow.  Otherwise new
readers like me have to come up with that association on our own.  But
since I'm proposing putting all this in the IOMMU code, it's totally
up to you :)

Bjorn

> +
>  /*
>   * find the upstream PCIe-to-PCI bridge of a PCI device
>   * if the device is PCIE, return NULL
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index bd8ec30..e87423a 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -1855,6 +1855,29 @@ static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
>  #endif
>
>  /**
> + * pci_walk_up_to_first_match - Generic upstream search function
> + * @pdev: starting PCI device to search
> + * @match: match function to call on each device (true = match)
> + * @last: last device examined prior to returned device
> + *
> + * Walk upstream from the given device, calling match() at each device.
> + * Returns the first device matching match().  If the root bus is reached
> + * without finding a match, return NULL.  last returns the N-1 step in
> + * the search path.
> + */
> +struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
> +                                          bool (*match)(struct pci_dev *),
> +                                          struct pci_dev **last);
> +
> +/**
> + * pci_is_pcie_bridge - Match a PCIe bridge device
> + * @pdev: device to test
> + *
> + * Return true if the given device is a PCIe bridge, false otherwise.
> + */
> +bool pci_is_pcie_bridge(struct pci_dev *pdev);
> +
> +/**
>   * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a device
>   * @pdev: the PCI device
>   *
>
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Patch

diff --git a/drivers/pci/search.c b/drivers/pci/search.c
index d0627fa..0357f74 100644
--- a/drivers/pci/search.c
+++ b/drivers/pci/search.c
@@ -17,6 +17,63 @@ 
 DECLARE_RWSEM(pci_bus_sem);
 EXPORT_SYMBOL_GPL(pci_bus_sem);
 
+/* Test for PCIe bridges. */
+bool pci_is_pcie_bridge(struct pci_dev *pdev)
+{
+	if (!pci_is_bridge(pdev))
+		return false;
+
+	if (pci_is_pcie(pdev))
+		return true;
+
+#ifdef CONFIG_PCI_QUIRKS
+	/*
+	 * If we're not on the root bus, look one device upstream of the
+	 * current device.  If that device is PCIe and is not a PCIe-to-PCI
+	 * bridge, then the current device is effectively PCIe as it must
+	 * be the PCIe-to-PCI bridge.  This handles several bridges that
+	 * violate the PCIe spec by not exposing a PCIe capability:
+	 * https://bugzilla.kernel.org/show_bug.cgi?id=44881
+	 */
+	if (!pci_is_root_bus(pdev->bus)) {
+		struct pci_dev *parent = pdev->bus->self;
+
+		if (pci_is_pcie(parent) &&
+		    pci_pcie_type(parent) != PCI_EXP_TYPE_PCI_BRIDGE)
+
+			return true;
+	}
+#endif
+	return false;
+}
+
+/*
+ * Walk upstream from the given pdev for the first device returning
+ * true for the provided match function.  If no match is found, return
+ * NULL.  *last records the previous step in the walk.
+ */
+struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
+					   bool (*match)(struct pci_dev *),
+					   struct pci_dev **last)
+{
+	*last = NULL;
+
+	if (match(pdev))
+		return pdev;
+
+	*last = pdev;
+
+	while (!pci_is_root_bus(pdev->bus)) {
+		*last = pdev;
+		pdev = pdev->bus->self;
+
+		if (match(pdev))
+			return pdev;
+	}
+
+	return NULL;
+}
+
 /*
  * find the upstream PCIe-to-PCI bridge of a PCI device
  * if the device is PCIE, return NULL
diff --git a/include/linux/pci.h b/include/linux/pci.h
index bd8ec30..e87423a 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -1855,6 +1855,29 @@  static inline struct eeh_dev *pci_dev_to_eeh_dev(struct pci_dev *pdev)
 #endif
 
 /**
+ * pci_walk_up_to_first_match - Generic upstream search function
+ * @pdev: starting PCI device to search
+ * @match: match function to call on each device (true = match)
+ * @last: last device examined prior to returned device
+ *
+ * Walk upstream from the given device, calling match() at each device.
+ * Returns the first device matching match().  If the root bus is reached
+ * without finding a match, return NULL.  last returns the N-1 step in
+ * the search path.
+ */
+struct pci_dev *pci_walk_up_to_first_match(struct pci_dev *pdev,
+					   bool (*match)(struct pci_dev *),
+					   struct pci_dev **last);
+
+/**
+ * pci_is_pcie_bridge - Match a PCIe bridge device
+ * @pdev: device to test
+ *
+ * Return true if the given device is a PCIe bridge, false otherwise.
+ */
+bool pci_is_pcie_bridge(struct pci_dev *pdev);
+
+/**
  * pci_find_upstream_pcie_bridge - find upstream PCIe-to-PCI bridge of a device
  * @pdev: the PCI device
  *