Messages in this thread | | | Subject | Re: [PATCH V6 02/13] pci, acpi: Provide generic way to assign bus domain number. | From | Tomasz Nowicki <> | Date | Mon, 2 May 2016 14:43:56 +0200 |
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On 04/27/2016 01:17 PM, Lorenzo Pieralisi wrote: > On Tue, Apr 26, 2016 at 09:26:49PM -0500, Bjorn Helgaas wrote: >> On Fri, Apr 15, 2016 at 07:06:37PM +0200, Tomasz Nowicki wrote: [...] >> >> +int acpi_pci_bus_domain_nr(struct device *parent) >> +{ >> + struct acpi_device *acpi_dev = to_acpi_device(parent); >> + unsigned long long segment = 0; >> + acpi_status status; >> + >> + /* >> + * If _SEG method does not exist, following ACPI spec (6.5.6) >> + * all PCI buses belong to domain 0. >> + */ >> + status = acpi_evaluate_integer(acpi_dev->handle, METHOD_NAME__SEG, NULL, >> + &segment); >> We already have code in acpi_pci_root_add() to evaluate _SEG. We >> don't want to evaluate it *twice*, do we? >> >> I was sort of expecting that if you added it here, we'd remove the >> existing call, but it looks like you're keeping both? > We can't remove the existing call, since it is used on X86 and IA64 > to store the segment number that, in the process, is used in their > pci_domain_nr() arch specific callback to retrieve the domain nr. > > On ARM64, that selects PCI_DOMAINS_GENERIC, we have to find a way > to retrieve the domain number that is not arch dependent, since > this is generic code, we can't rely on any bus->sysdata format (unless > we do something like JC did below), therefore the only way is to call > the _SEG method *again* here, which also forced Tomasz to go through > the ACPI_COMPANION setting song and dance and pass the parent pointer > to pci_create_root_bus() (see patch 1), which BTW is a source of > trouble on its own as you noticed. What trouble in patch 1 do you mean? I may miss something.
I agree that patch 1 is not necessary if we decide to use sysdata or rework root bus scanning to move domain to host bridge. Nevertheless, patch 1 is still a cleanup IMO.
Thanks, Tomasz
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