On 27.04.2016 04:45, Bjorn Helgaas wrote:

[question for Rafael below]

On Fri, Apr 15, 2016 at 07:06:36PM +0200, Tomasz Nowicki wrote:

quoted

Currently we have two platforms (x86 & ia64) capable of PCI ACPI host
bridge initialization. They both use arch-specific sysdata to pass down
parent device reference and both rely on NULL parent in pci_create_root_bus()
to validate sysdata content.

It looks hacky and prevents us from getting some firmware specific
info for PCI host controller based on its acpi_device structure
in generic pci_create_root_bus() function. However, we overcome that
blocker by passing down parent device via pci_create_root_bus parameter
(as the ACPI device type). Then we use ACPI_COMPANION_SET in core code
for ACPI boot method only. ACPI_COMPANION_SET is safe to run for all
cases DT, ACPI and DT&ACPI.

Since now PCI core code is setting ACPI companion device for us,
x86 & ia64 specific ACPI companion device setting turns out to be dead now.
We can get rid of it, including related companion reference from
PCI sysdata structure. Aslo, PCI_CONTROLLER macro cannot return valid
companion device anymore. Therefore we need to convert its usage to
ACPI_COMPANION.

Suggested-by: Lorenzo Pieralisi <redacted>
Signed-off-by: Tomasz Nowicki <redacted>
Reviewed-by: Lorenzo Pieralisi <redacted>
Tested-by: Duc Dang <redacted>
Tested-by: Dongdong Liu <redacted>
Tested-by: Hanjun Guo <redacted>
Tested-by: Graeme Gregory <redacted>
Tested-by: Sinan Kaya <redacted>
---
  arch/ia64/hp/common/sba_iommu.c    |  2 +-
  arch/ia64/include/asm/pci.h        |  1 -
  arch/ia64/pci/pci.c                | 16 ----------------
  arch/ia64/sn/kernel/io_acpi_init.c |  4 ++--
  arch/x86/include/asm/pci.h         |  3 ---
  arch/x86/pci/acpi.c                | 17 -----------------
  drivers/acpi/pci_root.c            |  7 ++++++-
  drivers/pci/probe.c                |  2 ++
  8 files changed, 11 insertions(+), 41 deletions(-)

diff --git a/arch/ia64/hp/common/sba_iommu.c b/arch/ia64/hp/common/sba_iommu.c
index a6d6190..78e4444 100644
--- a/arch/ia64/hp/common/sba_iommu.c
+++ b/arch/ia64/hp/common/sba_iommu.c

@@ -1981,7 +1981,7 @@ sba_connect_bus(struct pci_bus *bus)
  	if (PCI_CONTROLLER(bus)->iommu)
  		return;

-	handle = acpi_device_handle(PCI_CONTROLLER(bus)->companion);
+	handle = acpi_device_handle(ACPI_COMPANION(bus->bridge));
  	if (!handle)
  		return;

diff --git a/arch/ia64/include/asm/pci.h b/arch/ia64/include/asm/pci.h
index c0835b0..12423f4 100644
--- a/arch/ia64/include/asm/pci.h
+++ b/arch/ia64/include/asm/pci.h

@@ -63,7 +63,6 @@ extern int pci_mmap_legacy_page_range(struct pci_bus *bus,
  #define pci_legacy_write platform_pci_legacy_write

  struct pci_controller {
-	struct acpi_device *companion;
  	void *iommu;
  	int segment;
  	int node;		/* nearest node with memory or NUMA_NO_NODE for global allocation */

diff --git a/arch/ia64/pci/pci.c b/arch/ia64/pci/pci.c
index 8f6ac2f..978d6af 100644
--- a/arch/ia64/pci/pci.c
+++ b/arch/ia64/pci/pci.c

@@ -301,28 +301,12 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
  	}

  	info->controller.segment = root->segment;
-	info->controller.companion = device;
  	info->controller.node = acpi_get_node(device->handle);
  	INIT_LIST_HEAD(&info->io_resources);
  	return acpi_pci_root_create(root, &pci_acpi_root_ops,
  				    &info->common, &info->controller);
  }

-int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
-{
-	/*
-	 * We pass NULL as parent to pci_create_root_bus(), so if it is not NULL
-	 * here, pci_create_root_bus() has been called by someone else and
-	 * sysdata is likely to be different from what we expect.  Let it go in
-	 * that case.
-	 */
-	if (!bridge->dev.parent) {
-		struct pci_controller *controller = bridge->bus->sysdata;
-		ACPI_COMPANION_SET(&bridge->dev, controller->companion);
-	}
-	return 0;
-}
-
  void pcibios_fixup_device_resources(struct pci_dev *dev)
  {
  	int idx;

diff --git a/arch/ia64/sn/kernel/io_acpi_init.c b/arch/ia64/sn/kernel/io_acpi_init.c
index 231234c..e454492 100644
--- a/arch/ia64/sn/kernel/io_acpi_init.c
+++ b/arch/ia64/sn/kernel/io_acpi_init.c

@@ -132,7 +132,7 @@ sn_get_bussoft_ptr(struct pci_bus *bus)
  	struct acpi_resource_vendor_typed *vendor;


-	handle = acpi_device_handle(PCI_CONTROLLER(bus)->companion);
+	handle = acpi_device_handle(ACPI_COMPANION(bus->bridge));
  	status = acpi_get_vendor_resource(handle, METHOD_NAME__CRS,
  					  &sn_uuid, &buffer);
  	if (ACPI_FAILURE(status)) {

@@ -360,7 +360,7 @@ sn_acpi_get_pcidev_info(struct pci_dev *dev, struct pcidev_info **pcidev_info,
  	acpi_status status;
  	struct acpi_buffer name_buffer = { ACPI_ALLOCATE_BUFFER, NULL };

-	rootbus_handle = acpi_device_handle(PCI_CONTROLLER(dev)->companion);
+	rootbus_handle = acpi_device_handle(ACPI_COMPANION(dev->bus->bridge));
          status = acpi_evaluate_integer(rootbus_handle, METHOD_NAME__SEG, NULL,
                                         &segment);
          if (ACPI_SUCCESS(status)) {

diff --git a/arch/x86/include/asm/pci.h b/arch/x86/include/asm/pci.h
index 9ab7507..24de07d 100644
--- a/arch/x86/include/asm/pci.h
+++ b/arch/x86/include/asm/pci.h

@@ -14,9 +14,6 @@
  struct pci_sysdata {
  	int		domain;		/* PCI domain */
  	int		node;		/* NUMA node */
-#ifdef CONFIG_ACPI
-	struct acpi_device *companion;	/* ACPI companion device */
-#endif
  #ifdef CONFIG_X86_64
  	void		*iommu;		/* IOMMU private data */
  #endif

diff --git a/arch/x86/pci/acpi.c b/arch/x86/pci/acpi.c
index 3cd6983..f4ca17a 100644
--- a/arch/x86/pci/acpi.c
+++ b/arch/x86/pci/acpi.c

@@ -340,7 +340,6 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
  		struct pci_sysdata sd = {
  			.domain = domain,
  			.node = node,
-			.companion = root->device
  		};

  		memcpy(bus->sysdata, &sd, sizeof(sd));

@@ -355,7 +354,6 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
  		else {
  			info->sd.domain = domain;
  			info->sd.node = node;
-			info->sd.companion = root->device;
  			bus = acpi_pci_root_create(root, &acpi_pci_root_ops,
  						   &info->common, &info->sd);
  		}

@@ -373,21 +371,6 @@ struct pci_bus *pci_acpi_scan_root(struct acpi_pci_root *root)
  	return bus;
  }

-int pcibios_root_bridge_prepare(struct pci_host_bridge *bridge)
-{
-	/*
-	 * We pass NULL as parent to pci_create_root_bus(), so if it is not NULL
-	 * here, pci_create_root_bus() has been called by someone else and
-	 * sysdata is likely to be different from what we expect.  Let it go in
-	 * that case.
-	 */
-	if (!bridge->dev.parent) {
-		struct pci_sysdata *sd = bridge->bus->sysdata;
-		ACPI_COMPANION_SET(&bridge->dev, sd->companion);
-	}
-	return 0;
-}
-
  int __init pci_acpi_init(void)
  {
  	struct pci_dev *dev = NULL;

diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
index ae3fe4e..4581e0e 100644
--- a/drivers/acpi/pci_root.c
+++ b/drivers/acpi/pci_root.c

@@ -564,6 +564,11 @@ static int acpi_pci_root_add(struct acpi_device *device,
  		}
  	}

+	/*
+	 * pci_create_root_bus() needs to detect the parent device type,
+	 * so initialize its companion data accordingly.
+	 */
+	ACPI_COMPANION_SET(&device->dev, device);
  	root->device = device;
  	root->segment = segment & 0xFFFF;
  	strcpy(acpi_device_name(device), ACPI_PCI_ROOT_DEVICE_NAME);

@@ -846,7 +851,7 @@ struct pci_bus *acpi_pci_root_create(struct acpi_pci_root *root,

  	pci_acpi_root_add_resources(info);
  	pci_add_resource(&info->resources, &root->secondary);
-	bus = pci_create_root_bus(NULL, busnum, ops->pci_ops,
+	bus = pci_create_root_bus(&device->dev, busnum, ops->pci_ops,
  				  sysdata, &info->resources);

"device" here is a struct acpi_device *.  Rafael, is that the right
thing to do?  I dimly recall proposing something similar long ago and
that it turned out to be a bad idea.

Joining Bjorn's question. Rafael, do you recall what was the issue here 
from the past?

Thanks,
Tomasz