[PATCH V7 0/4] PCI: Add support for preserving boot configuration

[PATCH V7 0/4] PCI: Add support for preserving boot configuration

[Vidya Sagar]

Add support for preserving the boot configuration done by the
platform firmware per host bridge basis, based on the presence of
'linux,pci-probe-only' property in the respective PCI host bridge
device-tree node. It also unifies the ACPI and DT based boot flows
in this regard.

This patch series is a complete version of the incomplete series
( https://lore.kernel.org/linux-pci/20240421190914.374399-1-helgaas@kernel.org/ )
posted by Bjorn which in turn was an attempted split work of the single V6 patch
( https://lore.kernel.org/linux-pci/20240418174043.3750240-1-vidyas@nvidia.com/ )
posted by me.

Vidya Sagar (4):
  PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to
    pci_register_host_bridge()
  PCI: of: Add of_pci_preserve_config() for per-host bridge support
  PCI: Unify ACPI and DT 'preserve config' support
  PCI: Use preserve_config in place of pci_flags

 drivers/acpi/pci_root.c                  | 12 ------
 drivers/pci/controller/pci-host-common.c |  4 --
 drivers/pci/of.c                         | 54 +++++++++++++++++++-----
 drivers/pci/pci-acpi.c                   | 22 ++++++++++
 drivers/pci/pci.h                        | 12 ++++++
 drivers/pci/probe.c                      | 34 ++++++++++-----
 6 files changed, 101 insertions(+), 37 deletions(-)

-- 
2.25.1

[PATCH V7 1/4] PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to pci_register_host_bridge()

[Vidya Sagar]

Move the PRESERVE_BOOT_CONFIG _DSM evaluation from acpi_pci_root_create()
to pci_register_host_bridge().

This will help unify the ACPI _DSM path and the DT-based
"linux,pci-probe-only" paths.

This should be safe because it happens earlier than it used to:

    acpi_pci_root_create
      pci_create_root_bus
        pci_register_host_bridge
  +       bridge->preserve_config = pci_preserve_config(bridge)
            pci_acpi_preserve_config
  +           acpi_evaluate_dsm_typed(DSM_PCI_PRESERVE_BOOT_CONFIG)
  -   acpi_evaluate_dsm_typed(DSM_PCI_PRESERVE_BOOT_CONFIG)

No functional change intended.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
---
 drivers/acpi/pci_root.c | 12 ------------
 drivers/pci/pci-acpi.c  | 22 ++++++++++++++++++++++
 drivers/pci/pci.h       |  5 +++++
 drivers/pci/probe.c     | 11 +++++++++++
 4 files changed, 38 insertions(+), 12 deletions(-)

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index 58b89b8d950e..ddc2b3e89111 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c
@@ -1008,7 +1008,6 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
 	int node = acpi_get_node(device->handle);
 	struct pci_bus *bus;
 	struct pci_host_bridge *host_bridge;
-	union acpi_object *obj;
 
 	info->root = root;
 	info->bridge = device;
@@ -1050,17 +1049,6 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,
 	if (!(root->osc_ext_control_set & OSC_CXL_ERROR_REPORTING_CONTROL))
 		host_bridge->native_cxl_error = 0;
 
-	/*
-	 * Evaluate the "PCI Boot Configuration" _DSM Function.  If it
-	 * exists and returns 0, we must preserve any PCI resource
-	 * assignments made by firmware for this host bridge.
-	 */
-	obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(bus->bridge), &pci_acpi_dsm_guid, 1,
-				      DSM_PCI_PRESERVE_BOOT_CONFIG, NULL, ACPI_TYPE_INTEGER);
-	if (obj && obj->integer.value == 0)
-		host_bridge->preserve_config = 1;
-	ACPI_FREE(obj);
-
 	acpi_dev_power_up_children_with_adr(device);
 
 	pci_scan_child_bus(bus);
diff --git a/drivers/pci/pci-acpi.c b/drivers/pci/pci-acpi.c
index 004575091596..9cc447da9475 100644
--- a/drivers/pci/pci-acpi.c
+++ b/drivers/pci/pci-acpi.c
@@ -119,6 +119,28 @@ phys_addr_t acpi_pci_root_get_mcfg_addr(acpi_handle handle)
 	return (phys_addr_t)mcfg_addr;
 }
 
+bool pci_acpi_preserve_config(struct pci_host_bridge *host_bridge)
+{
+	if (ACPI_HANDLE(&host_bridge->dev)) {
+		union acpi_object *obj;
+
+		/*
+		 * Evaluate the "PCI Boot Configuration" _DSM Function.  If it
+		 * exists and returns 0, we must preserve any PCI resource
+		 * assignments made by firmware for this host bridge.
+		 */
+		obj = acpi_evaluate_dsm_typed(ACPI_HANDLE(&host_bridge->dev),
+					      &pci_acpi_dsm_guid,
+					      1, DSM_PCI_PRESERVE_BOOT_CONFIG,
+					      NULL, ACPI_TYPE_INTEGER);
+		if (obj && obj->integer.value == 0)
+			return true;
+		ACPI_FREE(obj);
+	}
+
+	return false;
+}
+
 /* _HPX PCI Setting Record (Type 0); same as _HPP */
 struct hpx_type0 {
 	u32 revision;		/* Not present in _HPP */
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 17fed1846847..180d3907b543 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -734,6 +734,7 @@ static inline void pci_restore_aer_state(struct pci_dev *dev) { }
 #endif
 
 #ifdef CONFIG_ACPI
+bool pci_acpi_preserve_config(struct pci_host_bridge *bridge);
 int pci_acpi_program_hp_params(struct pci_dev *dev);
 extern const struct attribute_group pci_dev_acpi_attr_group;
 void pci_set_acpi_fwnode(struct pci_dev *dev);
@@ -747,6 +748,10 @@ int acpi_pci_wakeup(struct pci_dev *dev, bool enable);
 bool acpi_pci_need_resume(struct pci_dev *dev);
 pci_power_t acpi_pci_choose_state(struct pci_dev *pdev);
 #else
+static inline bool pci_acpi_preserve_config(struct pci_host_bridge *bridge)
+{
+	return false;
+}
 static inline int pci_dev_acpi_reset(struct pci_dev *dev, bool probe)
 {
 	return -ENOTTY;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 1325fbae2f28..ee086d029450 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -889,6 +889,14 @@ static void pci_set_bus_msi_domain(struct pci_bus *bus)
 	dev_set_msi_domain(&bus->dev, d);
 }
 
+static bool pci_preserve_config(struct pci_host_bridge *host_bridge)
+{
+	if (pci_acpi_preserve_config(host_bridge))
+		return true;
+
+	return false;
+}
+
 static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 {
 	struct device *parent = bridge->dev.parent;
@@ -983,6 +991,9 @@ static int pci_register_host_bridge(struct pci_host_bridge *bridge)
 	if (nr_node_ids > 1 && pcibus_to_node(bus) == NUMA_NO_NODE)
 		dev_warn(&bus->dev, "Unknown NUMA node; performance will be reduced\n");
 
+	/* Check if the boot configuration by FW needs to be preserved */
+	bridge->preserve_config = pci_preserve_config(bridge);
+
 	/* Coalesce contiguous windows */
 	resource_list_for_each_entry_safe(window, n, &resources) {
 		if (list_is_last(&window->node, &resources))
-- 
2.25.1

[PATCH V7 2/4] PCI: of: Add of_pci_preserve_config() for per-host bridge support

[Vidya Sagar]

Add of_pci_preserve_config() to look for the "linux,pci-probe-only"
property under a specified node.  If it's not found there, look under
"of_chosen" in addition.

If the caller didn't specify a node, look under "of_chosen".

With a future patch, this will support "linux,pci-probe-only" on a per host
bridge basis based on the presence of the property in the respective PCI
host bridge DT node.

Implement of_pci_check_probe_only() using of_pci_preserve_config().

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
---
 drivers/pci/of.c  | 54 ++++++++++++++++++++++++++++++++++++++---------
 drivers/pci/pci.h |  7 ++++++
 2 files changed, 51 insertions(+), 10 deletions(-)

diff --git a/drivers/pci/of.c b/drivers/pci/of.c
index 51e3dd0ea5ab..d21c0bed36f3 100644
--- a/drivers/pci/of.c
+++ b/drivers/pci/of.c
@@ -234,27 +234,61 @@ int of_get_pci_domain_nr(struct device_node *node)
 EXPORT_SYMBOL_GPL(of_get_pci_domain_nr);
 
 /**
- * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
- *                           is present and valid
+ * of_pci_preserve_config - Return true if the boot configuration needs to
+ *                          be preserved
+ * @node: Device tree node.
+ *
+ * This function looks for "linux,pci-probe-only" property for a given
+ * PCI controller's node and returns true if found. It will also look in the
+ * chosen node if the property is not found in the given controller's node.
+ * Having this property ensures that the kernel doesn't reconfigure the
+ * BARs and bridge windows that are already done by the platform firmware.
+ *
+ * Return: true if the property exists false otherwise.
  */
-void of_pci_check_probe_only(void)
+bool of_pci_preserve_config(struct device_node *node)
 {
-	u32 val;
+	u32 val = 0;
 	int ret;
 
-	ret = of_property_read_u32(of_chosen, "linux,pci-probe-only", &val);
+	if (!node) {
+		pr_warn("device node is NULL, trying with of_chosen\n");
+		node = of_chosen;
+	}
+
+retry:
+	ret = of_property_read_u32(node, "linux,pci-probe-only", &val);
 	if (ret) {
-		if (ret == -ENODATA || ret == -EOVERFLOW)
-			pr_warn("linux,pci-probe-only without valid value, ignoring\n");
-		return;
+		if (ret == -ENODATA || ret == -EOVERFLOW) {
+			pr_warn("Incorrect value for linux,pci-probe-only in %pOF, ignoring\n",
+				node);
+			return false;
+		}
+		if (ret == -EINVAL) {
+			if (node == of_chosen)
+				return false;
+
+			node = of_chosen;
+			goto retry;
+		}
 	}
 
 	if (val)
+		return true;
+	else
+		return false;
+}
+
+/**
+ * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only
+ *                           is present and valid
+ */
+void of_pci_check_probe_only(void)
+{
+	if (of_pci_preserve_config(of_chosen))
 		pci_add_flags(PCI_PROBE_ONLY);
 	else
 		pci_clear_flags(PCI_PROBE_ONLY);
-
-	pr_info("PROBE_ONLY %s\n", val ? "enabled" : "disabled");
 }
 EXPORT_SYMBOL_GPL(of_pci_check_probe_only);
 
diff --git a/drivers/pci/pci.h b/drivers/pci/pci.h
index 180d3907b543..feedbedd65df 100644
--- a/drivers/pci/pci.h
+++ b/drivers/pci/pci.h
@@ -650,6 +650,7 @@ int of_pci_get_max_link_speed(struct device_node *node);
 u32 of_pci_get_slot_power_limit(struct device_node *node,
 				u8 *slot_power_limit_value,
 				u8 *slot_power_limit_scale);
+bool of_pci_preserve_config(struct device_node *node);
 int pci_set_of_node(struct pci_dev *dev);
 void pci_release_of_node(struct pci_dev *dev);
 void pci_set_bus_of_node(struct pci_bus *bus);
@@ -688,6 +689,12 @@ of_pci_get_slot_power_limit(struct device_node *node,
 	return 0;
 }
 
+static inline bool
+of_pci_preserve_config(struct device_node *node)
+{
+	return false;
+}
+
 static inline int pci_set_of_node(struct pci_dev *dev) { return 0; }
 static inline void pci_release_of_node(struct pci_dev *dev) { }
 static inline void pci_set_bus_of_node(struct pci_bus *bus) { }
-- 
2.25.1

[PATCH V7 3/4] PCI: Unify ACPI and DT 'preserve config' support

[Vidya Sagar]

Unify the 'preserve config' support across ACPI and device-tree
boot flows.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
---
 drivers/pci/probe.c | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index ee086d029450..2c232c22d6af 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -894,6 +894,9 @@ static bool pci_preserve_config(struct pci_host_bridge *host_bridge)
 	if (pci_acpi_preserve_config(host_bridge))
 		return true;
 
+	if (host_bridge->dev.parent && host_bridge->dev.parent->of_node)
+		return of_pci_preserve_config(host_bridge->dev.parent->of_node);
+
 	return false;
 }
 
-- 
2.25.1

[PATCH V7 4/4] PCI: Use preserve_config in place of pci_flags

[Vidya Sagar]

Use preserve_config in place of checking for PCI_PROBE_ONLY flag
to enable support for "linux,pci-probe-only" on a per host bridge
basis.

This patch also obviates the use of adding PCI_REASSIGN_ALL_BUS flag
if !PCI_PROBE_ONLY, as pci_assign_unassigned_root_bus_resources()
takes care of reassigning the resources that are not already claimed.

Signed-off-by: Vidya Sagar <vidyas@nvidia.com>
---
 drivers/pci/controller/pci-host-common.c |  4 ----
 drivers/pci/probe.c                      | 20 +++++++++-----------
 2 files changed, 9 insertions(+), 15 deletions(-)

diff --git a/drivers/pci/controller/pci-host-common.c b/drivers/pci/controller/pci-host-common.c
index 45b71806182d..c96b2de163b5 100644
--- a/drivers/pci/controller/pci-host-common.c
+++ b/drivers/pci/controller/pci-host-common.c
@@ -73,10 +73,6 @@ int pci_host_common_probe(struct platform_device *pdev)
 	if (IS_ERR(cfg))
 		return PTR_ERR(cfg);
 
-	/* Do not reassign resources if probe only */
-	if (!pci_has_flag(PCI_PROBE_ONLY))
-		pci_add_flags(PCI_REASSIGN_ALL_BUS);
-
 	bridge->sysdata = cfg;
 	bridge->ops = (struct pci_ops *)&ops->pci_ops;
 	bridge->msi_domain = true;
diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
index 2c232c22d6af..b4adc33f88cf 100644
--- a/drivers/pci/probe.c
+++ b/drivers/pci/probe.c
@@ -3088,20 +3088,18 @@ int pci_host_probe(struct pci_host_bridge *bridge)
 
 	bus = bridge->bus;
 
+	/* If we must preserve the resource configuration, claim now */
+	if (bridge->preserve_config)
+		pci_bus_claim_resources(bus);
+
 	/*
-	 * We insert PCI resources into the iomem_resource and
-	 * ioport_resource trees in either pci_bus_claim_resources()
-	 * or pci_bus_assign_resources().
+	 * Assign whatever was left unassigned. If we didn't claim above,
+	 * this will reassign everything.
 	 */
-	if (pci_has_flag(PCI_PROBE_ONLY)) {
-		pci_bus_claim_resources(bus);
-	} else {
-		pci_bus_size_bridges(bus);
-		pci_bus_assign_resources(bus);
+	pci_assign_unassigned_root_bus_resources(bus);
 
-		list_for_each_entry(child, &bus->children, node)
-			pcie_bus_configure_settings(child);
-	}
+	list_for_each_entry(child, &bus->children, node)
+		pcie_bus_configure_settings(child);
 
 	pci_bus_add_devices(bus);
 	return 0;
-- 
2.25.1

RE: [PATCH V7 0/4] PCI: Add support for preserving boot configuration

[Vidya Sagar]

Hi Bjorn,
Thanks for reviewing and refactoring V6 patch.
Could you please review this V7 series as well?

Thanks,
Vidya Sagar

> -----Original Message-----
> From: Vidya Sagar <vidyas@nvidia.com>
> Sent: Wednesday, May 8, 2024 11:12 PM
> To: bhelgaas@google.com; rafael@kernel.org; lenb@kernel.org; will@kernel.org;
> lpieralisi@kernel.org; kw@linux.com; robh@kernel.org; frowand.list@gmail.com
> Cc: linux-pci@vger.kernel.org; linux-acpi@vger.kernel.org; linux-
> kernel@vger.kernel.org; linux-arm-kernel@lists.infradead.org;
> devicetree@vger.kernel.org; Thierry Reding <treding@nvidia.com>; Jon Hunter
> <jonathanh@nvidia.com>; Krishna Thota <kthota@nvidia.com>; Manikanta
> Maddireddy <mmaddireddy@nvidia.com>; Vidya Sagar <vidyas@nvidia.com>;
> sagar.tv@gmail.com
> Subject: [PATCH V7 0/4] PCI: Add support for preserving boot configuration
> 
> Add support for preserving the boot configuration done by the platform firmware
> per host bridge basis, based on the presence of 'linux,pci-probe-only' property in
> the respective PCI host bridge device-tree node. It also unifies the ACPI and DT
> based boot flows in this regard.
> 
> This patch series is a complete version of the incomplete series (
> https://lore.kernel.org/linux-pci/20240421190914.374399-1-
> helgaas@kernel.org/ ) posted by Bjorn which in turn was an attempted split work
> of the single V6 patch ( https://lore.kernel.org/linux-
> pci/20240418174043.3750240-1-vidyas@nvidia.com/ ) posted by me.
> 
> Vidya Sagar (4):
>   PCI: Move PRESERVE_BOOT_CONFIG _DSM evaluation to
>     pci_register_host_bridge()
>   PCI: of: Add of_pci_preserve_config() for per-host bridge support
>   PCI: Unify ACPI and DT 'preserve config' support
>   PCI: Use preserve_config in place of pci_flags
> 
>  drivers/acpi/pci_root.c                  | 12 ------
>  drivers/pci/controller/pci-host-common.c |  4 --
>  drivers/pci/of.c                         | 54 +++++++++++++++++++-----
>  drivers/pci/pci-acpi.c                   | 22 ++++++++++
>  drivers/pci/pci.h                        | 12 ++++++
>  drivers/pci/probe.c                      | 34 ++++++++++-----
>  6 files changed, 101 insertions(+), 37 deletions(-)
> 
> --
> 2.25.1