linux-kernel - Re: [Linaro-acpi] [PATCH V1 10/11] pci, acpi: Provide generic way to assign bus domain number.

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Date:	Wed, 4 Nov 2015 11:04:58 +0100
From:	Tomasz Nowicki <tomasz.nowicki@...aro.org>
To:	Lorenzo Pieralisi <lorenzo.pieralisi@....com>,
	Tomasz Nowicki <tn@...ihalf.com>
Cc:	rjw@...ysocki.net, linux-kernel@...r.kernel.org, arnd@...db.de,
	linux-acpi@...r.kernel.org, linux-pci@...r.kernel.org,
	catalin.marinas@....com, linaro-acpi@...ts.linaro.org,
	will.deacon@....com, ddaney@...iumnetworks.com,
	Narinder.Dhillon@...iumnetworks.com, wangyijing@...wei.com,
	robert.richter@...iumnetworks.com, tglx@...utronix.de,
	bhelgaas@...gle.com, Liviu.Dudau@....com,
	jiang.liu@...ux.intel.com, linux-arm-kernel@...ts.infradead.org
Subject: Re: [Linaro-acpi] [PATCH V1 10/11] pci, acpi: Provide generic way to
 assign bus domain number.

On 03.11.2015 17:10, Lorenzo Pieralisi wrote:
> On Tue, Oct 27, 2015 at 05:38:41PM +0100, Tomasz Nowicki wrote:
>> Architectures which support PCI_DOMAINS_GENERIC (like ARM64)
>> cannot call pci_bus_assign_domain_nr along ACPI PCI host bridge
>> initialization since this function needs valid parent device reference
>> to be able to retrieve domain number (aka segment).
>>
>> We can omit that blocker and pass down host bridge device via
>> pci_create_root_bus parameter and then be able to evaluate _SEG method
>> being in pci_bus_assign_domain_nr.
>>
>> Note that _SEG method is optional, therefore _SEG absence means
>> that all PCI buses belong to domain 0.
>>
>> Signed-off-by: Tomasz Nowicki <tn@...ihalf.com>
>> ---
>>   drivers/acpi/pci_root.c |  2 +-
>>   drivers/pci/pci.c       | 32 +++++++++++++++++++++++++++-----
>>   2 files changed, 28 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/acpi/pci_root.c b/drivers/acpi/pci_root.c
>> index 850d7bf..e682dc6 100644
>> --- a/drivers/acpi/pci_root.c
>> +++ b/drivers/acpi/pci_root.c
>> @@ -839,7 +839,7 @@ 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);
>
> If I read x86 code correctly, they rely on the first argument to be
> NULL, I think you would break x86 by doing that, see:
>
> arch/x86/pci/acpi.c (pcibios_root_bridge_prepare())
>
> By the way, can't we move the code setting up the ACPI_COMPANION
> to core PCI code and stop relying on sysdata for that ?
>

Yes, that will break x86&ia64 but as you said it may be overcome with 
consolidation of ACPI_COMPANION into the core code.

Tomasz
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