Re: [PATCH V6 01/13] pci, acpi, x86, ia64: Move ACPI host bridge device companion assignment to core code.

Rafael J. Wysocki
2016-05-09T22:18:59Z

On Wednesday, May 04, 2016 10:10:58 AM Tomasz Nowicki wrote:
> 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:
> >> 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 <lorenzo.pieralisi@arm.com>
> >> Signed-off-by: Tomasz Nowicki <tn@semihalf.com>
> >> Reviewed-by: Lorenzo Pieralisi <lorenzo.pieralisi@arm.com>
> >> Tested-by: Duc Dang <dhdang@apm.com>
> >> Tested-by: Dongdong Liu <liudongdong3@huawei.com>
> >> Tested-by: Hanjun Guo <hanjun.guo@linaro.org>
> >> Tested-by: Graeme Gregory <graeme.gregory@linaro.org>
> >> Tested-by: Sinan Kaya <okaya@codeaurora.org>
> >> ---
> >> 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?

Yes, I do.

Anything struct acpi_device doesn't represent a real device. It represents
a firmware object that can be associated with a device. IOW, nothing under
LNXSYSTM\:00/ should ever be used as the parent or sibling etc with respect to
anything outside of that directory. In fact, the entire LNXSYSTM\:00/ should
be located under /sys/firmware/acpi/ and it was a mistake to put it under
/sys/devices/.

One immediate consequence of the above change, AFAICS, would be that the whole
PCI hierarchy would now hang under /sys/devices/LNXSYSTM\:00/LNXSYBUS\:00/PNP0A08\:00/
which would not make any sense whatever, because
/sys/devices/LNXSYSTM\:00/LNXSYBUS\:00/PNP0A08\:00/physical_node already points to
/sys/devices/pci0000\:00/.

IOW, both PNP0A08\:00/ and pci0000\:00/ already represent the same thing, ie. the
host bridge.

If you want to have a parent for pci0000\:00/, you need a physical_node for
LNXSYBUS\:00 and point to that as the parent from pci0000\:00/. That at least
will lead to a sysfs hierarchy that makes sense, although it may break user
space tools I suppose (which may be assuming that pci0000\:00/ will always be
present directly under /sys/devices/).

Thanks,
Rafael