[RFC PATCH 0/3] PCI/ASPM: Remove unncessary linked list in aspm.c

[RFC PATCH 0/3] PCI/ASPM: Remove unncessary linked list in aspm.c

[Saheed O. Bolarinwa]

From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

An extra linked list is created inside aspm.c to keep track of devices
on which the link state was enabled. However, it is possible to access
them via existing device lists.

This series remove the extra linked list and other related members of
the struct pcie_link_state: `root`, `parent` and `downstream`. All these
are now either calculated or obtained directly when needed.

Bolarinwa O. Saheed (4):
  PCI/ASPM: Remove struct pcie_link_state.parent
  PCI/ASPM: Remove struct pcie_link_state.root
  PCI/ASPM: Remove struct pcie_link_state.downstream
  PCI/ASPM: Remove unncessary linked list defined within aspm.c

 drivers/pci/pcie/aspm.c | 121 +++++++++++++++++++++-------------------
 1 file changed, 64 insertions(+), 57 deletions(-)

-- 
2.20.1

[RFC PATCH 1/4] PCI/ASPM: Remove struct pcie_link_state.parent

[Saheed O. Bolarinwa]

From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

Information cached in struct pcie_link_state.parent is accessible
via struct pci_dev.

This patch:
 - removes *parent* from the *struct pcie_link_state*
 - adjusts all references to it to access the information directly

Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
---
OPINION: the checkpatch.pl scring warns on this line:
	`BUG_ON(root->pdev->bus->parent->self);`
however, I think if a root device reports a parent, that is serious!

 drivers/pci/pcie/aspm.c | 18 +++++++++++-------
 1 file changed, 11 insertions(+), 7 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 013a47f587ce..48b83048aa30 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -50,7 +50,6 @@ struct pcie_link_state {
 	struct pci_dev *pdev;		/* Upstream component of the Link */
 	struct pci_dev *downstream;	/* Downstream component, function 0 */
 	struct pcie_link_state *root;	/* pointer to the root port link */
-	struct pcie_link_state *parent;	/* pointer to the parent Link state */
 	struct list_head sibling;	/* node in link_list */
 
 	/* ASPM state */
@@ -379,6 +378,7 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
 static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 {
 	u32 latency, l1_switch_latency = 0;
+	struct pci_dev *parent;
 	struct aspm_latency *acceptable;
 	struct pcie_link_state *link;
 
@@ -419,7 +419,8 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
 			link->aspm_capable &= ~ASPM_STATE_L1;
 		l1_switch_latency += 1000;
 
-		link = link->parent;
+		parent = link->pdev->bus->parent->self;
+		link = !parent ? NULL : parent->link_state;
 	}
 }
 
@@ -793,9 +794,11 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
 
 static void pcie_config_aspm_path(struct pcie_link_state *link)
 {
+	struct pci_dev *parent;
 	while (link) {
 		pcie_config_aspm_link(link, policy_to_aspm_state(link));
-		link = link->parent;
+		parent = link->pdev->bus->parent->self;
+		link = !parent ? NULL : parent->link_state;
 	}
 }
 
@@ -872,8 +875,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
 			return NULL;
 		}
 
-		link->parent = parent;
-		link->root = link->parent->root;
+		link->root = parent->root;
 	}
 
 	list_add(&link->sibling, &link_list);
@@ -962,7 +964,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 static void pcie_update_aspm_capable(struct pcie_link_state *root)
 {
 	struct pcie_link_state *link;
-	BUG_ON(root->parent);
+	BUG_ON(root->pdev->bus->parent->self);
 	list_for_each_entry(link, &link_list, sibling) {
 		if (link->root != root)
 			continue;
@@ -985,6 +987,7 @@ static void pcie_update_aspm_capable(struct pcie_link_state *root)
 /* @pdev: the endpoint device */
 void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 {
+	struct pci_dev *parent_dev;
 	struct pci_dev *parent = pdev->bus->self;
 	struct pcie_link_state *link, *root, *parent_link;
 
@@ -1002,7 +1005,8 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 
 	link = parent->link_state;
 	root = link->root;
-	parent_link = link->parent;
+	parent_dev = link->pdev->bus->parent->self;
+	parent_link = !parent_dev ? NULL : parent_dev->link_state;
 
 	/* All functions are removed, so just disable ASPM for the link */
 	pcie_config_aspm_link(link, 0);
-- 
2.20.1

[RFC PATCH 2/4] PCI/ASPM: Remove struct pcie_link_state.root

[Saheed O. Bolarinwa]

From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

Information on the root device is cached in
struct pcie_link_state.root it obtained within
alloc_pcie_link_state().

This patch:
 - creates *pcie_get_root()* which return the root pci_dev
   of a pci_dev.
 - removes *root* from the *struct pcie_link_state*.
 - replaces references to struct pcie_link_state.root with
   a call to pcie_get_root().

Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
---
 drivers/pci/pcie/aspm.c | 63 +++++++++++++++++++++--------------------
 1 file changed, 32 insertions(+), 31 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 48b83048aa30..8772a4ea4365 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -49,7 +49,6 @@ struct aspm_latency {
 struct pcie_link_state {
 	struct pci_dev *pdev;		/* Upstream component of the Link */
 	struct pci_dev *downstream;	/* Downstream component, function 0 */
-	struct pcie_link_state *root;	/* pointer to the root port link */
 	struct list_head sibling;	/* node in link_list */
 
 	/* ASPM state */
@@ -843,6 +842,25 @@ static int pcie_aspm_sanity_check(struct pci_dev *pdev)
 	return 0;
 }
 
+/*
+ * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe
+ * hierarchies.  Note that some PCIe host implementations omit
+ * the root ports entirely, in which case a downstream port on
+ * a switch may become the root of the link state chain for all
+ * its subordinate endpoints.
+ */
+static struct pci_dev *pcie_get_root(struct pci_dev *pdev)
+{
+	struct pci_dev *parent = pdev->bus->parent->self;
+
+	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
+	    pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE || !parent) {
+		return pdev;
+	} else {
+		return pcie_get_root(parent);
+	}
+}
+
 static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
 {
 	struct pcie_link_state *link;
@@ -855,29 +873,6 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
 	link->pdev = pdev;
 	link->downstream = pci_function_0(pdev->subordinate);
 
-	/*
-	 * Root Ports and PCI/PCI-X to PCIe Bridges are roots of PCIe
-	 * hierarchies.  Note that some PCIe host implementations omit
-	 * the root ports entirely, in which case a downstream port on
-	 * a switch may become the root of the link state chain for all
-	 * its subordinate endpoints.
-	 */
-	if (pci_pcie_type(pdev) == PCI_EXP_TYPE_ROOT_PORT ||
-	    pci_pcie_type(pdev) == PCI_EXP_TYPE_PCIE_BRIDGE ||
-	    !pdev->bus->parent->self) {
-		link->root = link;
-	} else {
-		struct pcie_link_state *parent;
-
-		parent = pdev->bus->parent->self->link_state;
-		if (!parent) {
-			kfree(link);
-			return NULL;
-		}
-
-		link->root = parent->root;
-	}
-
 	list_add(&link->sibling, &link_list);
 	pdev->link_state = link;
 	return link;
@@ -963,18 +958,23 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 /* Recheck latencies and update aspm_capable for links under the root */
 static void pcie_update_aspm_capable(struct pcie_link_state *root)
 {
+	struct pci_dev *dev;
 	struct pcie_link_state *link;
 	BUG_ON(root->pdev->bus->parent->self);
 	list_for_each_entry(link, &link_list, sibling) {
-		if (link->root != root)
+		dev = pcie_get_root(link->pdev);
+		if (dev->link_state != root)
 			continue;
+
 		link->aspm_capable = link->aspm_support;
 	}
 	list_for_each_entry(link, &link_list, sibling) {
 		struct pci_dev *child;
 		struct pci_bus *linkbus = link->pdev->subordinate;
-		if (link->root != root)
+		dev = pcie_get_root(link->pdev);
+		if (dev->link_state != root)
 			continue;
+
 		list_for_each_entry(child, &linkbus->devices, bus_list) {
 			if ((pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT) &&
 			    (pci_pcie_type(child) != PCI_EXP_TYPE_LEG_END))
@@ -987,9 +987,9 @@ static void pcie_update_aspm_capable(struct pcie_link_state *root)
 /* @pdev: the endpoint device */
 void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 {
-	struct pci_dev *parent_dev;
+	struct pci_dev *parent_dev, *root_dev;
 	struct pci_dev *parent = pdev->bus->self;
-	struct pcie_link_state *link, *root, *parent_link;
+	struct pcie_link_state *link, *parent_link;
 
 	if (!parent || !parent->link_state)
 		return;
@@ -1004,7 +1004,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 		goto out;
 
 	link = parent->link_state;
-	root = link->root;
+	root_dev = pcie_get_root(link->pdev);
 	parent_dev = link->pdev->bus->parent->self;
 	parent_link = !parent_dev ? NULL : parent_dev->link_state;
 
@@ -1016,7 +1016,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 
 	/* Recheck latencies and configure upstream links */
 	if (parent_link) {
-		pcie_update_aspm_capable(root);
+		pcie_update_aspm_capable(root_dev->link_state);
 		pcie_config_aspm_path(parent_link);
 	}
 out:
@@ -1028,6 +1028,7 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 void pcie_aspm_pm_state_change(struct pci_dev *pdev)
 {
 	struct pcie_link_state *link = pdev->link_state;
+	struct pci_dev *root = pcie_get_root(pdev);
 
 	if (aspm_disabled || !link)
 		return;
@@ -1037,7 +1038,7 @@ void pcie_aspm_pm_state_change(struct pci_dev *pdev)
 	 */
 	down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
-	pcie_update_aspm_capable(link->root);
+	pcie_update_aspm_capable(root->link_state);
 	pcie_config_aspm_path(link);
 	mutex_unlock(&aspm_lock);
 	up_read(&pci_bus_sem);
-- 
2.20.1

[RFC PATCH 3/4] PCI/ASPM: Remove struct pcie_link_state.downstream

[Saheed O. Bolarinwa]

From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

Information on the downstream component is cached in
struct pcie_link_state.downstream it obtained within
alloc_pcie_link_state() by calling pci_function_0()

This patch:
 - removes *downstream* from *struct pcie_link_state*.
 - replaces references to pcie_link_state.downstream with
   a call to pci_function_0(pdev->subordinate).

Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
---
 drivers/pci/pcie/aspm.c | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 8772a4ea4365..516a6f07ac6e 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -48,7 +48,6 @@ struct aspm_latency {
 
 struct pcie_link_state {
 	struct pci_dev *pdev;		/* Upstream component of the Link */
-	struct pci_dev *downstream;	/* Downstream component, function 0 */
 	struct list_head sibling;	/* node in link_list */
 
 	/* ASPM state */
@@ -452,7 +451,8 @@ static void pci_clear_and_set_dword(struct pci_dev *pdev, int pos,
 static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 				u32 parent_l1ss_cap, u32 child_l1ss_cap)
 {
-	struct pci_dev *child = link->downstream, *parent = link->pdev;
+	struct pci_dev *parent = link->pdev;
+	struct pci_dev *child = pci_function_0(link->pdev->subordinate);
 	u32 val1, val2, scale1, scale2;
 	u32 t_common_mode, t_power_on, l1_2_threshold, scale, value;
 	u32 ctl1 = 0, ctl2 = 0;
@@ -542,7 +542,8 @@ static void aspm_calc_l1ss_info(struct pcie_link_state *link,
 
 static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 {
-	struct pci_dev *child = link->downstream, *parent = link->pdev;
+	struct pci_dev *parent = link->pdev;
+	struct pci_dev *child = pci_function_0(link->pdev->subordinate);
 	u32 parent_lnkcap, child_lnkcap;
 	u16 parent_lnkctl, child_lnkctl;
 	u32 parent_l1ss_cap, child_l1ss_cap;
@@ -684,7 +685,8 @@ static void pcie_aspm_cap_init(struct pcie_link_state *link, int blacklist)
 static void pcie_config_aspm_l1ss(struct pcie_link_state *link, u32 state)
 {
 	u32 val, enable_req;
-	struct pci_dev *child = link->downstream, *parent = link->pdev;
+	struct pci_dev *parent = link->pdev;
+	struct pci_dev *child = pci_function_0(link->pdev->subordinate);
 
 	enable_req = (link->aspm_enabled ^ state) & state;
 
@@ -743,7 +745,8 @@ static void pcie_config_aspm_dev(struct pci_dev *pdev, u32 val)
 static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
 {
 	u32 upstream = 0, dwstream = 0;
-	struct pci_dev *child = link->downstream, *parent = link->pdev;
+	struct pci_dev *parent = link->pdev;
+	struct pci_dev *child = pci_function_0(link->pdev->subordinate);
 	struct pci_bus *linkbus = parent->subordinate;
 
 	/* Enable only the states that were not explicitly disabled */
@@ -871,7 +874,6 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
 
 	INIT_LIST_HEAD(&link->sibling);
 	link->pdev = pdev;
-	link->downstream = pci_function_0(pdev->subordinate);
 
 	list_add(&link->sibling, &link_list);
 	pdev->link_state = link;
-- 
2.20.1

[RFC PATCH 4/4] PCI/ASPM: Remove unncessary linked list defined within aspm.c

[Saheed O. Bolarinwa]

From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>

aspm.c defines a linked list - `link_list` and stores each of
its node in struct pcie_link_state.sibling. This linked list
tracks devices for which the struct pcie_link_state object
was successfully created. It is used to loop through the list
for instance to set ASPM policy or update changes. However, it
is possible to access these devices via existing lists defined
inside pci.h

This patch:
- removes link_list and struct pcie_link_state.sibling
- accesses child devices via struct pci_dev.bust_list
- accesses all PCI buses via pci_root_buses on struct pci_bus.node

Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
---
 drivers/pci/pcie/aspm.c | 40 ++++++++++++++++++++--------------------
 1 file changed, 20 insertions(+), 20 deletions(-)

diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
index 516a6f07ac6e..35bc16c00b32 100644
--- a/drivers/pci/pcie/aspm.c
+++ b/drivers/pci/pcie/aspm.c
@@ -48,7 +48,6 @@ struct aspm_latency {
 
 struct pcie_link_state {
 	struct pci_dev *pdev;		/* Upstream component of the Link */
-	struct list_head sibling;	/* node in link_list */
 
 	/* ASPM state */
 	u32 aspm_support:7;		/* Supported ASPM state */
@@ -76,7 +75,6 @@ struct pcie_link_state {
 static int aspm_disabled, aspm_force;
 static bool aspm_support_enabled = true;
 static DEFINE_MUTEX(aspm_lock);
-static LIST_HEAD(link_list);
 
 #define POLICY_DEFAULT 0	/* BIOS default setting */
 #define POLICY_PERFORMANCE 1	/* high performance */
@@ -872,10 +870,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
 	if (!link)
 		return NULL;
 
-	INIT_LIST_HEAD(&link->sibling);
 	link->pdev = pdev;
-
-	list_add(&link->sibling, &link_list);
 	pdev->link_state = link;
 	return link;
 }
@@ -961,21 +956,16 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
 static void pcie_update_aspm_capable(struct pcie_link_state *root)
 {
 	struct pci_dev *dev;
+	struct pci_bus *rootbus = root->pdev->bus;
 	struct pcie_link_state *link;
 	BUG_ON(root->pdev->bus->parent->self);
-	list_for_each_entry(link, &link_list, sibling) {
-		dev = pcie_get_root(link->pdev);
-		if (dev->link_state != root)
-			continue;
-
-		link->aspm_capable = link->aspm_support;
+	list_for_each_entry(dev, &rootbus->devices, bus_list) {
+		dev->link_state->aspm_capable = link->aspm_support;
 	}
-	list_for_each_entry(link, &link_list, sibling) {
+
+	list_for_each_entry(dev, &rootbus->devices, bus_list) {
 		struct pci_dev *child;
-		struct pci_bus *linkbus = link->pdev->subordinate;
-		dev = pcie_get_root(link->pdev);
-		if (dev->link_state != root)
-			continue;
+		struct pci_bus *linkbus = dev->subordinate;
 
 		list_for_each_entry(child, &linkbus->devices, bus_list) {
 			if ((pci_pcie_type(child) != PCI_EXP_TYPE_ENDPOINT) &&
@@ -1012,7 +1002,6 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
 
 	/* All functions are removed, so just disable ASPM for the link */
 	pcie_config_aspm_link(link, 0);
-	list_del(&link->sibling);
 	/* Clock PM is for endpoint device */
 	free_link_state(link);
 
@@ -1152,6 +1141,8 @@ static int pcie_aspm_set_policy(const char *val,
 {
 	int i;
 	struct pcie_link_state *link;
+	struct pci_bus *bus;
+	struct pci_dev *pdev;
 
 	if (aspm_disabled)
 		return -EPERM;
@@ -1164,9 +1155,18 @@ static int pcie_aspm_set_policy(const char *val,
 	down_read(&pci_bus_sem);
 	mutex_lock(&aspm_lock);
 	aspm_policy = i;
-	list_for_each_entry(link, &link_list, sibling) {
-		pcie_config_aspm_link(link, policy_to_aspm_state(link));
-		pcie_set_clkpm(link, policy_to_clkpm_state(link));
+	list_for_each_entry(bus, &pci_root_buses, node) {
+		list_for_each_entry(pdev, &bus->devices, bus_list) {
+			if (!pci_is_pcie(pdev))
+				break;
+
+			link = pdev->link_state;
+			if (!link)
+				continue;
+
+			pcie_config_aspm_link(link, policy_to_aspm_state(link));
+			pcie_set_clkpm(link, policy_to_clkpm_state(link));
+		}
 	}
 	mutex_unlock(&aspm_lock);
 	up_read(&pci_bus_sem);
-- 
2.20.1

Re: [RFC PATCH 1/4] PCI/ASPM: Remove struct pcie_link_state.parent

[Bjorn Helgaas]

On Thu, Sep 16, 2021 at 10:52:03AM +0200, Saheed O. Bolarinwa wrote:
> From: "Bolarinwa O. Saheed" <refactormyself@gmail.com>
> 
> Information cached in struct pcie_link_state.parent is accessible
> via struct pci_dev.
> 
> This patch:
>  - removes *parent* from the *struct pcie_link_state*
>  - adjusts all references to it to access the information directly
> 
> Signed-off-by: Bolarinwa O. Saheed <refactormyself@gmail.com>
> ---
> OPINION: the checkpatch.pl scring warns on this line:
> 	`BUG_ON(root->pdev->bus->parent->self);`
> however, I think if a root device reports a parent, that is serious!

Do you mean this warning?

  WARNING: Missing a blank line after declarations
  #967: FILE: drivers/pci/pcie/aspm.c:967:
  +	struct pcie_link_state *link;
  +	BUG_ON(root->pdev->bus->parent->self);

That's just complaining about a blank line, so no big deal.  You could
resolve that by adding the blank line in this patch.

The fact that we use BUG_ON() at all *is* a real problem.  See the
comments at the BUG() definition.  We should rework this so that
condition is either impossible and we can just remove the BUG_ON(), or
we can deal with it gracefully.  But this would be material for a
different patch.

>  drivers/pci/pcie/aspm.c | 18 +++++++++++-------
>  1 file changed, 11 insertions(+), 7 deletions(-)
> 
> diff --git a/drivers/pci/pcie/aspm.c b/drivers/pci/pcie/aspm.c
> index 013a47f587ce..48b83048aa30 100644
> --- a/drivers/pci/pcie/aspm.c
> +++ b/drivers/pci/pcie/aspm.c
> @@ -50,7 +50,6 @@ struct pcie_link_state {
>  	struct pci_dev *pdev;		/* Upstream component of the Link */
>  	struct pci_dev *downstream;	/* Downstream component, function 0 */
>  	struct pcie_link_state *root;	/* pointer to the root port link */
> -	struct pcie_link_state *parent;	/* pointer to the parent Link state */
>  	struct list_head sibling;	/* node in link_list */
>  
>  	/* ASPM state */
> @@ -379,6 +378,7 @@ static void encode_l12_threshold(u32 threshold_us, u32 *scale, u32 *value)
>  static void pcie_aspm_check_latency(struct pci_dev *endpoint)
>  {
>  	u32 latency, l1_switch_latency = 0;
> +	struct pci_dev *parent;
>  	struct aspm_latency *acceptable;
>  	struct pcie_link_state *link;
>  
> @@ -419,7 +419,8 @@ static void pcie_aspm_check_latency(struct pci_dev *endpoint)
>  			link->aspm_capable &= ~ASPM_STATE_L1;
>  		l1_switch_latency += 1000;
>  
> -		link = link->parent;
> +		parent = link->pdev->bus->parent->self;
> +		link = !parent ? NULL : parent->link_state;

I love the direction of this patch, but this chain of pointers
(link->pdev->bus->parent->self) is a little over the top and is
repeated several times here.

Can we simplify it a bit by making a helper function?  It's similar
but not quite the same as pci_upstream_bridge().

And maybe reverse the condition to avoid the negation?

  link = parent ? parent->link_state : NULL;

>  	}
>  }
>  
> @@ -793,9 +794,11 @@ static void pcie_config_aspm_link(struct pcie_link_state *link, u32 state)
>  
>  static void pcie_config_aspm_path(struct pcie_link_state *link)
>  {
> +	struct pci_dev *parent;
>  	while (link) {
>  		pcie_config_aspm_link(link, policy_to_aspm_state(link));
> -		link = link->parent;
> +		parent = link->pdev->bus->parent->self;
> +		link = !parent ? NULL : parent->link_state;
>  	}
>  }
>  
> @@ -872,8 +875,7 @@ static struct pcie_link_state *alloc_pcie_link_state(struct pci_dev *pdev)
>  			return NULL;
>  		}
>  
> -		link->parent = parent;
> -		link->root = link->parent->root;
> +		link->root = parent->root;
>  	}
>  
>  	list_add(&link->sibling, &link_list);
> @@ -962,7 +964,7 @@ void pcie_aspm_init_link_state(struct pci_dev *pdev)
>  static void pcie_update_aspm_capable(struct pcie_link_state *root)
>  {
>  	struct pcie_link_state *link;
> -	BUG_ON(root->parent);
> +	BUG_ON(root->pdev->bus->parent->self);
>  	list_for_each_entry(link, &link_list, sibling) {
>  		if (link->root != root)
>  			continue;
> @@ -985,6 +987,7 @@ static void pcie_update_aspm_capable(struct pcie_link_state *root)
>  /* @pdev: the endpoint device */
>  void pcie_aspm_exit_link_state(struct pci_dev *pdev)
>  {
> +	struct pci_dev *parent_dev;
>  	struct pci_dev *parent = pdev->bus->self;
>  	struct pcie_link_state *link, *root, *parent_link;
>  
> @@ -1002,7 +1005,8 @@ void pcie_aspm_exit_link_state(struct pci_dev *pdev)
>  
>  	link = parent->link_state;
>  	root = link->root;
> -	parent_link = link->parent;
> +	parent_dev = link->pdev->bus->parent->self;
> +	parent_link = !parent_dev ? NULL : parent_dev->link_state;
>  
>  	/* All functions are removed, so just disable ASPM for the link */
>  	pcie_config_aspm_link(link, 0);
> -- 
> 2.20.1
>