From: wangyijing@huawei•com (Yijing Wang)
To: linux-arm-kernel@lists•infradead.org
Subject: [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr
Date: Tue, 9 Sep 2014 13:54:21 +0800 [thread overview]
Message-ID: <540E960D.7080408@huawei.com> (raw)
In-Reply-To: <20140908155931.GP27864@e106497-lin.cambridge.arm.com>
>>> on new requests. This function gets called quite a lot and I'm trying not to
>>> make it too heavy weight.
>>
>> Generally, nothing should be accessing the same DT value frequently.
>> It should get cached somewhere.
>>
>
> The problem appears for DTs that don't have the pci-domain info. Then the cached
> value is left at the default non-valid value and attempts to rescan the DT will
> be made every time the function is called.
>
>> I don't really understand how domains are used so it's hard to provide
>> a recommendation here. Do domains even belong in the DT?
>
> ACPI calls them segments and the way Bjorn explained it to me at some moment was
> that it was an attempt to split up a bus in different groups (or alternatively,
> merge a few busses together). To be honest I haven't seen systems where the domain
> is anything other than zero, but JasonG (or maybe Benjamin) were floating an
> idea of using the domain number to identify physical slots.
PCI domain(or named segment) is provided by firmware, in ACPI system, we evaluated it
by method "_SEG". in IA64 with ACPI, PCI hostbridge driver retrieves the domain from ACPI,
if it's absent, the default domain is zero. So I wonder why in DTS, if it's absent, we get
a auto increment domain value.
PCI get domain by ACPI "_SEG" in IA64(drivers/acpi/pci_root.c)
......
status = acpi_evaluate_integer(handle, METHOD_NAME__SEG, NULL,
&segment);
if (ACPI_FAILURE(status) && status != AE_NOT_FOUND) {
dev_err(&device->dev, "can't evaluate _SEG\n");
result = -ENODEV;
goto end;
}
.......
Thanks!
Yijing.
>
>> This function
>> is just a weird mixture of data retrieval and allocation. I think you
>> need to separate it into 2 functions.
>
> It is meant to do allocation with the retrieval being a short-cut (or fine
> control if you want).
>
> I need to think a bit more for a better solution.
>
> Best regards,
> Liviu
>
>>
>> Rob
>>
>
--
Thanks!
Yijing
next prev parent reply other threads:[~2014-09-09 5:54 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-09-08 13:54 [PATCH v10 00/10] Support for creating generic PCI host bridges from DT Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 01/10] Fix ioport_map() for !CONFIG_GENERIC_IOMAP cases Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 02/10] PCI: Introduce helper functions to deal with PCI I/O ranges Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 03/10] ARM: Define PCI_IOBASE as the base of virtual PCI IO space Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 04/10] PCI: OF: Fix the conversion of IO ranges into IO resources Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 05/10] PCI: Create pci_host_bridge before its associated bus in pci_create_root_bus Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 06/10] PCI: Introduce generic domain handling for PCI busses Liviu Dudau
2014-09-08 14:03 ` Catalin Marinas
2014-09-08 14:05 ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 07/10] OF: Introduce helper function for getting PCI domain_nr Liviu Dudau
2014-09-08 14:27 ` Rob Herring
2014-09-08 14:54 ` Liviu Dudau
2014-09-08 15:27 ` Rob Herring
2014-09-08 15:59 ` Liviu Dudau
2014-09-08 16:39 ` Jason Gunthorpe
2014-09-09 5:54 ` Yijing Wang [this message]
2014-09-09 8:46 ` Liviu Dudau
2014-09-09 9:16 ` Arnd Bergmann
2014-09-09 11:20 ` Catalin Marinas
2014-09-10 18:19 ` Arnd Bergmann
2014-09-11 14:11 ` Phil Edworthy
2014-09-11 14:49 ` Arnd Bergmann
2014-09-09 14:17 ` Bjorn Helgaas
2014-09-09 9:30 ` Yijing Wang
2014-09-09 14:11 ` Liviu Dudau
2014-09-10 1:44 ` Yijing Wang
2014-09-09 14:26 ` Bjorn Helgaas
2014-09-09 15:41 ` Jason Gunthorpe
2014-09-10 2:44 ` Rob Herring
2014-09-10 16:32 ` Jason Gunthorpe
2014-09-10 1:55 ` Yijing Wang
2014-09-10 13:04 ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 08/10] OF: PCI: Add support for parsing PCI host bridge resources from DT Liviu Dudau
2014-09-09 13:35 ` Lorenzo Pieralisi
2014-09-10 14:22 ` Liviu Dudau
2014-09-10 15:10 ` Lorenzo Pieralisi
2014-09-10 15:32 ` Liviu Dudau
2014-09-10 16:37 ` Lorenzo Pieralisi
2014-09-10 16:53 ` Liviu Dudau
2014-09-10 17:06 ` Lorenzo Pieralisi
2014-09-08 13:54 ` [PATCH v10 09/10] PCI: Assign unassigned bus resources in pci_scan_root_bus() Liviu Dudau
2014-09-12 10:13 ` Suravee Suthikulpanit
2014-09-12 10:34 ` Liviu Dudau
2014-09-08 13:54 ` [PATCH v10 10/10] PCI: Introduce pci_remap_iospace() for remapping PCI I/O bus resources into CPU space Liviu Dudau
2014-09-08 16:07 ` [PATCH v10 00/10] Support for creating generic PCI host bridges from DT Liviu Dudau
2014-09-12 8:25 ` Suravee Suthikulpanit
2014-09-12 9:30 ` Liviu Dudau
2014-09-12 10:00 ` Suravee Suthikulpanit
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