linux-kernel - Re: [PATCH v7 4/6] pci: Introduce a domain number for pci_host

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Date:	Thu, 10 Apr 2014 15:53:04 +0100
From:	Liviu Dudau <Liviu.Dudau@....com>
To:	Arnd Bergmann <arnd@...db.de>
Cc:	Bjorn Helgaas <bhelgaas@...gle.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	linux-pci <linux-pci@...r.kernel.org>,
	Catalin Marinas <Catalin.Marinas@....com>,
	Will Deacon <Will.Deacon@....com>,
	linaro-kernel <linaro-kernel@...ts.linaro.org>,
	LKML <linux-kernel@...r.kernel.org>,
	"devicetree@...r.kernel.org" <devicetree@...r.kernel.org>,
	LAKML <linux-arm-kernel@...ts.infradead.org>,
	Tanmay Inamdar <tinamdar@....com>,
	Grant Likely <grant.likely@...retlab.ca>
Subject: Re: [PATCH v7 4/6] pci: Introduce a domain number for
 pci_host_bridge.

On Thu, Apr 10, 2014 at 03:07:44PM +0100, Arnd Bergmann wrote:
> On Thursday 10 April 2014 07:50:52 Bjorn Helgaas wrote:
> > On Thu, Apr 10, 2014 at 2:00 AM, Arnd Bergmann <arnd@...db.de> wrote:
> > > On Wednesday 09 April 2014 21:48:14 Bjorn Helgaas wrote:
> > >> On Wed, Apr 9, 2014 at 7:27 PM, Liviu Dudau <liviu@...au.co.uk> wrote:
> > >> > On Wed, Apr 09, 2014 at 08:02:41AM -0600, Bjorn Helgaas wrote:
> > >> >> >>   struct pci_host_bridge {
> > >> >> >>     int domain;
> > >> >> >>     int node;
> > >> >> >>     struct device *dev;
> > >> >> >>     struct pci_ops *ops;
> > >> >> >>     struct list_head resources;
> > >> >> >>     void *sysdata;
> > >> >> >>     struct pci_bus *bus;  /* filled in by core, not by arch */
> > >> >> >>     ... /* other existing contents managed by core */
> > >> >> >>   };
> > >> >> >>
> > >> >> >>   struct pci_bus *pci_scan_host_bridge(struct pci_host_bridge *bridge);
> > >> >> >
> > 
> > I'm not sure I'm following you; you mean the arch-specific sysdata
> > structure would contain a pointer to struct pci_host_bridge?
> > 
> > I have to admit that I'm not up on how other subsystems handle this
> > sort of abstraction.  Do you have any pointers to good examples that I
> > can study?
> 
> What I mean is like this:
> 
> /* generic structure */
> struct pci_host_bridge {
>         int domain;
>         int node;
>         struct device *dev;
>         struct pci_ops *ops; 
>         struct list_head resources;
>         struct pci_bus *bus;  /* filled in by core, not by arch */
>         ... /* other existing contents managed by core */
> };
> 
> /* arm specific structure */
> struct pci_sys_data {
>         char            io_res_name[12];
>                                         /* Bridge swizzling                     */
>         u8              (*swizzle)(struct pci_dev *, u8 *);
>                                         /* IRQ mapping                          */
>         int             (*map_irq)(const struct pci_dev *, u8, u8);
>                                         /* Resource alignement requirements     */
>         void            (*add_bus)(struct pci_bus *bus);
>         void            (*remove_bus)(struct pci_bus *bus);
>         void            *private_data;  /* platform controller private data     */
> 
> 	/* not a pointer: */
> 	struct pci_host_bridge bridge;
> };
> static inline struct pci_sys_data *to_pci_sys_data(struct pci_host_bridge *bridge)
> {
> 	return container_of(bridge, struct pci_sys_data, bridge);
> }
> 
> /* arm specific, driver specific structure */
> struct tegra_pcie {
>         void __iomem *pads;
>         void __iomem *afi;
> 
>         struct clk *pex_clk;
>         struct clk *afi_clk;
>         struct clk *pll_e;
>         struct clk *cml_clk;
> 
>         struct tegra_msi msi;
> 
>         struct list_head ports;
>         unsigned int num_ports;
> 
> 	struct pci_sys_data sysdata;
> };
> static inline struct tegra_pcie *to_tegra_pcie(struct pci_sys_data *sysdata)
> {
> 	return container_of(sysdata, struct tegra_pcie, sysdata);
> }
> 
> This mirrors how we treat devices: a pci_device has an embedded device,
> and so on, in other subsystems we can have multiple layers.
> 
> In this example, the tegra pcie driver then allocates its own tegra_pcie
> structure, fills out the fields it needs, and registers it with the
> ARM architecture code, passing just the pci_sys_data pointer. That function
> in turn passes a pointer to the embedded pci_host_bridge down to the
> generic code. Ideally we should try to eliminate the architecture specific
> portion here, but that is a later step.

So Arnd seems to agree with me: we should try to get out of architecture specific
pci_sys_data and link the host bridge driver straight into the PCI core. The
core then can call into arch code via pcibios_*() functions.

Arnd, am I reading correctly into what you are saying?

Liviu

> 
> 	Arnd
> --
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> 
> 

-- 
====================
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| but they're not |
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