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* [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
@ 2020-06-22 16:12 Mika Westerberg
  2020-06-30 22:01 ` Bjorn Helgaas
  0 siblings, 1 reply; 6+ messages in thread
From: Mika Westerberg @ 2020-06-22 16:12 UTC (permalink / raw)
  To: Bjorn Helgaas; +Cc: Kalle Valo, Yicong Yang, Mika Westerberg, linux-pci

Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
pci_find_pcie_root_port()") unified the root port finding functionality
into a single function but missed the fact that the passed in device may
already be a root port. This causes the kernel to block power management
of PCIe hierarchies in recent systems because ->bridge_d3 started to
return false for such ports after the commit in question.

Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
Cc: stable@vger.kernel.org
---
 include/linux/pci.h | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c79d83304e52..c17c24f5eeed 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2169,8 +2169,13 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
  */
 static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
 {
-	struct pci_dev *bridge = pci_upstream_bridge(dev);
+	struct pci_dev *bridge;
 
+	/* If dev is already root port */
+	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+		return dev;
+
+	bridge = pci_upstream_bridge(dev);
 	while (bridge) {
 		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
 			return bridge;
-- 
2.27.0


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
  2020-06-22 16:12 [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well Mika Westerberg
@ 2020-06-30 22:01 ` Bjorn Helgaas
  2020-07-01  1:53   ` Yicong Yang
  2020-07-01 10:14   ` Mika Westerberg
  0 siblings, 2 replies; 6+ messages in thread
From: Bjorn Helgaas @ 2020-06-30 22:01 UTC (permalink / raw)
  To: Mika Westerberg; +Cc: Bjorn Helgaas, Kalle Valo, Yicong Yang, linux-pci

On Mon, Jun 22, 2020 at 07:12:48PM +0300, Mika Westerberg wrote:
> Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
> pci_find_pcie_root_port()") unified the root port finding functionality
> into a single function but missed the fact that the passed in device may
> already be a root port. This causes the kernel to block power management
> of PCIe hierarchies in recent systems because ->bridge_d3 started to
> return false for such ports after the commit in question.
> 
> Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> Cc: stable@vger.kernel.org
> ---
>  include/linux/pci.h | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
> 
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index c79d83304e52..c17c24f5eeed 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2169,8 +2169,13 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
>   */
>  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
>  {
> -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> +	struct pci_dev *bridge;
>  
> +	/* If dev is already root port */
> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> +		return dev;
> +
> +	bridge = pci_upstream_bridge(dev);
>  	while (bridge) {
>  		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
>  			return bridge;

I applied the patch below, which is slightly simplified but I think
still equivalent, to for-linus for v5.8.  Let me know if it's not.

I dropped the stable tag because 6ae72bfa656e was merged for v5.8-rc1,
and I assume v5.7 works correctly so it doesn't need any change.


commit 5396956cc7c6 ("PCI: Make pcie_find_root_port() work for Root Ports")
Author: Mika Westerberg <mika.westerberg@linux.intel.com>
Date:   Mon Jun 22 19:12:48 2020 +0300

    PCI: Make pcie_find_root_port() work for Root Ports
    
    Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
    pci_find_pcie_root_port()") broke acpi_pci_bridge_d3() because calling
    pcie_find_root_port() on a Root Port returned NULL when it should return
    the Root Port, which in turn broke power management of PCIe hierarchies.
    
    Rework pcie_find_root_port() so it returns its argument when it is already
    a Root Port.
    
    [bhelgaas: test device only once, test for PCIe]
    Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
    Link: https://lore.kernel.org/r/20200622161248.51099-1-mika.westerberg@linux.intel.com
    Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
    Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>

diff --git a/include/linux/pci.h b/include/linux/pci.h
index c79d83304e52..34c1c4f45288 100644
--- a/include/linux/pci.h
+++ b/include/linux/pci.h
@@ -2169,12 +2169,11 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
  */
 static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
 {
-	struct pci_dev *bridge = pci_upstream_bridge(dev);
-
-	while (bridge) {
-		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
-			return bridge;
-		bridge = pci_upstream_bridge(bridge);
+	while (dev) {
+		if (pci_is_pcie(dev) &&
+		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
+			return dev;
+		dev = pci_upstream_bridge(dev);
 	}
 
 	return NULL;

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
  2020-06-30 22:01 ` Bjorn Helgaas
@ 2020-07-01  1:53   ` Yicong Yang
  2020-07-01 10:15     ` Mika Westerberg
  2020-07-01 10:14   ` Mika Westerberg
  1 sibling, 1 reply; 6+ messages in thread
From: Yicong Yang @ 2020-07-01  1:53 UTC (permalink / raw)
  To: Bjorn Helgaas, Mika Westerberg; +Cc: Bjorn Helgaas, Kalle Valo, linux-pci

Hi Bjorn,


On 2020/7/1 6:01, Bjorn Helgaas wrote:
> On Mon, Jun 22, 2020 at 07:12:48PM +0300, Mika Westerberg wrote:
>> Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
>> pci_find_pcie_root_port()") unified the root port finding functionality
>> into a single function but missed the fact that the passed in device may
>> already be a root port. This causes the kernel to block power management
>> of PCIe hierarchies in recent systems because ->bridge_d3 started to
>> return false for such ports after the commit in question.
>>
>> Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
>> Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>> Cc: stable@vger.kernel.org
>> ---
>>  include/linux/pci.h | 7 ++++++-
>>  1 file changed, 6 insertions(+), 1 deletion(-)
>>
>> diff --git a/include/linux/pci.h b/include/linux/pci.h
>> index c79d83304e52..c17c24f5eeed 100644
>> --- a/include/linux/pci.h
>> +++ b/include/linux/pci.h
>> @@ -2169,8 +2169,13 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
>>   */
>>  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
>>  {
>> -	struct pci_dev *bridge = pci_upstream_bridge(dev);
>> +	struct pci_dev *bridge;
>>  
>> +	/* If dev is already root port */
>> +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
>> +		return dev;
>> +
>> +	bridge = pci_upstream_bridge(dev);
>>  	while (bridge) {
>>  		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
>>  			return bridge;
> I applied the patch below, which is slightly simplified but I think
> still equivalent, to for-linus for v5.8.  Let me know if it's not.
>
> I dropped the stable tag because 6ae72bfa656e was merged for v5.8-rc1,
> and I assume v5.7 works correctly so it doesn't need any change.
>
>
> commit 5396956cc7c6 ("PCI: Make pcie_find_root_port() work for Root Ports")
> Author: Mika Westerberg <mika.westerberg@linux.intel.com>
> Date:   Mon Jun 22 19:12:48 2020 +0300
>
>     PCI: Make pcie_find_root_port() work for Root Ports
>     
>     Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
>     pci_find_pcie_root_port()") broke acpi_pci_bridge_d3() because calling
>     pcie_find_root_port() on a Root Port returned NULL when it should return
>     the Root Port, which in turn broke power management of PCIe hierarchies.
>     
>     Rework pcie_find_root_port() so it returns its argument when it is already
>     a Root Port.
>     
>     [bhelgaas: test device only once, test for PCIe]
>     Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
>     Link: https://lore.kernel.org/r/20200622161248.51099-1-mika.westerberg@linux.intel.com
>     Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
>     Signed-off-by: Bjorn Helgaas <bhelgaas@google.com>
>
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index c79d83304e52..34c1c4f45288 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -2169,12 +2169,11 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
>   */
>  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
>  {
> -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> -
> -	while (bridge) {
> -		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> -			return bridge;
> -		bridge = pci_upstream_bridge(bridge);
> +	while (dev) {
> +		if (pci_is_pcie(dev) &&
> +		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> +			return dev;
> +		dev = pci_upstream_bridge(dev);
>  	}
>  

We may have some problems here, as after pcie_find_root_port() called, *dev will
be either root port or NULL but users may want it unchanged. One such usage is
in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin
after called this.

So we should use a temporary point to *dev rather than directly modify it.

Thanks,
Yicong


>  	return NULL;
> .
>


^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
  2020-06-30 22:01 ` Bjorn Helgaas
  2020-07-01  1:53   ` Yicong Yang
@ 2020-07-01 10:14   ` Mika Westerberg
  1 sibling, 0 replies; 6+ messages in thread
From: Mika Westerberg @ 2020-07-01 10:14 UTC (permalink / raw)
  To: Bjorn Helgaas; +Cc: Bjorn Helgaas, Kalle Valo, Yicong Yang, linux-pci

On Tue, Jun 30, 2020 at 05:01:07PM -0500, Bjorn Helgaas wrote:
> On Mon, Jun 22, 2020 at 07:12:48PM +0300, Mika Westerberg wrote:
> > Commit 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and
> > pci_find_pcie_root_port()") unified the root port finding functionality
> > into a single function but missed the fact that the passed in device may
> > already be a root port. This causes the kernel to block power management
> > of PCIe hierarchies in recent systems because ->bridge_d3 started to
> > return false for such ports after the commit in question.
> > 
> > Fixes: 6ae72bfa656e ("PCI: Unify pcie_find_root_port() and pci_find_pcie_root_port()")
> > Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
> > Cc: stable@vger.kernel.org
> > ---
> >  include/linux/pci.h | 7 ++++++-
> >  1 file changed, 6 insertions(+), 1 deletion(-)
> > 
> > diff --git a/include/linux/pci.h b/include/linux/pci.h
> > index c79d83304e52..c17c24f5eeed 100644
> > --- a/include/linux/pci.h
> > +++ b/include/linux/pci.h
> > @@ -2169,8 +2169,13 @@ static inline int pci_pcie_type(const struct pci_dev *dev)
> >   */
> >  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> >  {
> > -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> > +	struct pci_dev *bridge;
> >  
> > +	/* If dev is already root port */
> > +	if (pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> > +		return dev;
> > +
> > +	bridge = pci_upstream_bridge(dev);
> >  	while (bridge) {
> >  		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> >  			return bridge;
> 
> I applied the patch below, which is slightly simplified but I think
> still equivalent, to for-linus for v5.8.  Let me know if it's not.

Thanks I just tested and it also works fine.

> I dropped the stable tag because 6ae72bfa656e was merged for v5.8-rc1,
> and I assume v5.7 works correctly so it doesn't need any change.

Right, makes sense.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
  2020-07-01  1:53   ` Yicong Yang
@ 2020-07-01 10:15     ` Mika Westerberg
  2020-07-01 12:47       ` Yicong Yang
  0 siblings, 1 reply; 6+ messages in thread
From: Mika Westerberg @ 2020-07-01 10:15 UTC (permalink / raw)
  To: Yicong Yang; +Cc: Bjorn Helgaas, Bjorn Helgaas, Kalle Valo, linux-pci

On Wed, Jul 01, 2020 at 09:53:51AM +0800, Yicong Yang wrote:
> >  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
> >  {
> > -	struct pci_dev *bridge = pci_upstream_bridge(dev);
> > -
> > -	while (bridge) {
> > -		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
> > -			return bridge;
> > -		bridge = pci_upstream_bridge(bridge);
> > +	while (dev) {
> > +		if (pci_is_pcie(dev) &&
> > +		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
> > +			return dev;
> > +		dev = pci_upstream_bridge(dev);
> >  	}
> >  
> 
> We may have some problems here, as after pcie_find_root_port() called, *dev will
> be either root port or NULL but users may want it unchanged. One such usage is
> in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin
> after called this.
> 
> So we should use a temporary point to *dev rather than directly modify it.

dev is already a copy of what is passed by the caller so it does not
matter if it gets changed here. You would need to pass it through struct
pci_dev **dev in order to modify the passed pointer.

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well
  2020-07-01 10:15     ` Mika Westerberg
@ 2020-07-01 12:47       ` Yicong Yang
  0 siblings, 0 replies; 6+ messages in thread
From: Yicong Yang @ 2020-07-01 12:47 UTC (permalink / raw)
  To: Mika Westerberg; +Cc: Bjorn Helgaas, Bjorn Helgaas, Kalle Valo, linux-pci

On 2020/7/1 18:15, Mika Westerberg wrote:
> On Wed, Jul 01, 2020 at 09:53:51AM +0800, Yicong Yang wrote:
>>>  static inline struct pci_dev *pcie_find_root_port(struct pci_dev *dev)
>>>  {
>>> -	struct pci_dev *bridge = pci_upstream_bridge(dev);
>>> -
>>> -	while (bridge) {
>>> -		if (pci_pcie_type(bridge) == PCI_EXP_TYPE_ROOT_PORT)
>>> -			return bridge;
>>> -		bridge = pci_upstream_bridge(bridge);
>>> +	while (dev) {
>>> +		if (pci_is_pcie(dev) &&
>>> +		    pci_pcie_type(dev) == PCI_EXP_TYPE_ROOT_PORT)
>>> +			return dev;
>>> +		dev = pci_upstream_bridge(dev);
>>>  	}
>>>  
>> We may have some problems here, as after pcie_find_root_port() called, *dev will
>> be either root port or NULL but users may want it unchanged. One such usage is
>> in acpi_pci_bridge_d3(), drivers/pci/pci-acpi.c, *dev is used as origin
>> after called this.
>>
>> So we should use a temporary point to *dev rather than directly modify it.
> dev is already a copy of what is passed by the caller so it does not
> matter if it gets changed here. You would need to pass it through struct
> pci_dev **dev in order to modify the passed pointer.

Ah...I must be fuzzy in mind then. Thanks.


> .
>


^ permalink raw reply	[flat|nested] 6+ messages in thread

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Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2020-06-22 16:12 [PATCH] PCI: Make pcie_find_root_port() work for PCIe root ports as well Mika Westerberg
2020-06-30 22:01 ` Bjorn Helgaas
2020-07-01  1:53   ` Yicong Yang
2020-07-01 10:15     ` Mika Westerberg
2020-07-01 12:47       ` Yicong Yang
2020-07-01 10:14   ` Mika Westerberg

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