linux-kernel - Re: [PATCH v10 00/10] Support for creating generic PCI host bridges from DT

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Message-ID: <5412ADE9.2050708@amd.com>
Date:	Fri, 12 Sep 2014 03:25:13 -0500
From:	Suravee Suthikulpanit <suravee.suthikulpanit@....com>
To:	Liviu Dudau <Liviu.Dudau@....com>,
	Bjorn Helgaas <bhelgaas@...gle.com>,
	Arnd Bergmann <arnd@...db.de>,
	Rob Herring <robh+dt@...nel.org>,
	"Jason Gunthorpe" <jgunthorpe@...idianresearch.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Catalin Marinas <catalin.marinas@....com>,
	"Will Deacon" <Will.Deacon@....com>,
	Russell King <linux@....linux.org.uk>,
	linux-pci <linux-pci@...r.kernel.org>,
	Linus Walleij <linus.walleij@...aro.org>
CC:	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>,
	Sinan Kaya <okaya@...eaurora.org>,
	Jingoo Han <jg1.han@...sung.com>,
	Kukjin Kim <kgene.kim@...sung.com>,
	linux-arch <linux-arch@...r.kernel.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"Device Tree ML" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>
Subject: Re: [PATCH v10 00/10] Support for creating generic PCI host bridges
 from DT

On 9/8/2014 8:54 AM, Liviu Dudau wrote:
> This is my version 10 of the attempt at adding support for generic PCI host
> bridge controllers that make use of device tree information to
> configure themselves. This version reverses v9's attempt to create one function
> to drive the whole process of extracting the host bridge ranges, setup the
> host bridge driver and then scan the root bus behind the host bridge. While it
> would've been quite user friendly, I agree that it would've caused a lot of pain
> in the future.
>
> I would like to get ACKs for the remaining patches as I would like to integrate
> this into -next in the following week.
>
> This version marks an implementation break with the previous versions as
> of_create_pci_host_bridge() is now gone. It gets replaced by
> of_pci_get_host_bridge_resources() that only parses the DT and extracts the
> relevant ranges and converts them to resources. The updated host bridge drivers
> will have to follow the guidelines in this example code:
>
> static int foohb_probe(struct platform_device *pdev)
> {
> 	struct device_node *dn = pdev->dev.of_node;
> 	struct foohb_drv *drv;
> 	resource_size_t io_base = 0;  /* phys address for start of IO */
> 	struct pci_bus *bus;
> 	int err = 0;
> 	LIST_HEAD(res);
>
> 	.....
> 	err = of_pci_get_host_bridge_resources(dn, 0, 255, &res, &io_base);
> 	if (err)
> 		goto err_handling;
> 	err = foohb_setup(drv, ...., &res, &io_base);
> 	if (err)
> 		goto err_handling;

My understanding is that the "foohb_setup" above is supposed to be equivalent
to the "int (*setup)(struct pci_host_bridge *, resource_size_t)" in V9 that was
passed in as an argument of "of_create_pci_hot_bridge()".

The problem I have is I need an intermediate step between "pci_create_root_bus()"
and "pci_scan_child_bus()" in order to update the information such as the "pci_bus->msi"
before this is propagate down to the child bus during the "pci_scan_child_bus"
which is also called in the pci_scan_root_bus() function.

Does this mean that I should not be calling the pci_scan_root_bus(), and tries to
re-implement the same logic in my driver?

Thanks,

Suravee

> 	.....
> 	pci_add_flags(....);
> 	bus = pci_scan_root_bus(&pdev->dev, 0, &foohb_ops, drv, &res);
> 	if (!bus)
> 		goto err_handling;
> 	....
> 	return 0;
>
> err_handling:
> 	......
> 	return err;
> }
>


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