linux-kernel - Re: Need help on Linux PCIe

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Message-ID: <CAD6G_RR=toq_6tCav6Y9=EprK9LC3YfGO=scvWpcGfDpWwJbRA@mail.gmail.com>
Date:	Wed, 4 Dec 2013 11:50:26 +0530
From:	Jagan Teki <jagannadh.teki@...il.com>
To:	Bjorn Helgaas <bhelgaas@...gle.com>
Cc:	"linux-pci@...r.kernel.org" <linux-pci@...r.kernel.org>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: Need help on Linux PCIe

Thanks for your quick response.
Please find my comments below.

On Tue, Dec 3, 2013 at 11:09 PM, Bjorn Helgaas <bhelgaas@...gle.com> wrote:
> On Tue, Dec 3, 2013 at 4:24 AM, Jagan Teki <jagannadh.teki@...il.com> wrote:
>> Hi,
>>
>> I have few question on Linux PCIe subsystem, I am trying to understand
>> the PCIe on ARM platform.
>> 1. Compared to PCI, PCIe have an extra port functionalists/services
>> which is implemented drivers/pci/pcie/* is it true?
>
> Yes.
>
>> 2. PCIe root complex is same as Host controller drivers in linux drivers/host/*
>
> Yes.
>
>> 3. As individual endpoint drivers are registered to pci_core as
>> pci_driver_register, then what is the common call for registering
>> individual HC driver to pci-core?
>
> The host controller-PCI core interface is not as mature as the
> pci_register_driver() interface.  The basic interface is
> pci_scan_root_bus().  If you skim through the drivers in
> drivers/pci/host/* and drivers/acpi/pci_root.c, the interface to the
> PCI core will be fairly obvious.  And you'll learn what the existing
> practices are in case you need to add or modify something.

OK.

I understand the flow as below - please correct if am wrong.

>From low level (hw) - HC driver has a platform registration using
platform_driver_register() to lower layer
and then pci_scan_root_bus() --> pci_common_init_dev() registration to
upper layer as PCI - BIOS and then ends.

>From upper level (app) - each endpoint driver has
pci_driver_register() call to PCI Core for lower level and then the
upper
level registration is based on endpoint().

What is the connection here for PCI-BIOS and PCI-Core here, does these
are two different entities means there is no common call for these?
I see for ARM - "arch/arm/kernel/bios32.c" is PCI-BIOS is it correct?
does we have separate BIOS codes for architectures?

-- 
Thanks,
Jagan.
--------
Jagannadha Sutradharudu Teki,
E: jagannadh.teki@...il.com, P: +91-9676773388
Engineer - System Software Hacker
U-boot - SPI Custodian and Zynq APSOC
Ln: http://www.linkedin.com/in/jaganteki
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