Re: [PATCH v9 07/30] PCI: Add default bus resource in pci_host_bridge

[Bjorn Helgaas]

On Fri, Apr 03, 2015 at 05:25:41PM +0800, Yijing Wang wrote:
> If there is no busn resource provided for pci_scan_root_bus(),
> we would insert a default bus resource (root_bus_number, 255)
> in root bus, and update the max bus number we found after
> pci_scan_child_bus(). We also need to hold the default bus
> resource in pci_host_bridge, then we could identify whether
> the new pci host bridge conflict with existing one.
> 
> Signed-off-by: Yijing Wang <wangyijing@xxxxxxxxxx>
> ---
>  drivers/pci/host-bridge.c |   20 ++++++++++++++++++++
>  drivers/pci/probe.c       |   26 ++++++++++----------------
>  include/linux/pci.h       |    2 ++
>  3 files changed, 32 insertions(+), 16 deletions(-)
> 
> diff --git a/drivers/pci/host-bridge.c b/drivers/pci/host-bridge.c
> index 7d52a0a..ecc1a7c 100644
> --- a/drivers/pci/host-bridge.c
> +++ b/drivers/pci/host-bridge.c
> @@ -19,6 +19,25 @@ static void pci_release_host_bridge_dev(struct device *dev)
>  	kfree(bridge);
>  }
>  
> +static void pci_host_update_busn_res(
> +		struct pci_host_bridge *host, int bus,
> +		struct list_head *resources)
> +{
> +	struct resource_entry *window;
> +
> +	resource_list_for_each_entry(window, resources)
> +		if (window->res->flags & IORESOURCE_BUS)
> +			return;
> +
> +	pr_info(
> +	 "No busn resource found for pci%04x:%02x, will use [bus %02x-ff]\n",
> +		host->domain, bus, bus);
> +	host->busn_res.flags = IORESOURCE_BUS;
> +	host->busn_res.start = bus;
> +	host->busn_res.end = 255;
> +	pci_add_resource(resources, &host->busn_res);
> +}
> +
>  struct pci_host_bridge *pci_create_host_bridge(
>  		struct device *parent, int domain, int bus,
>  		struct list_head *resources)
> @@ -33,6 +52,7 @@ struct pci_host_bridge *pci_create_host_bridge(
>  
>  	host->dev.parent = parent;
>  	INIT_LIST_HEAD(&host->windows);
> +	pci_host_update_busn_res(host, bus, resources);
>  	resource_list_for_each_entry_safe(window, n, resources)
>  		list_move_tail(&window->node, &host->windows);
>  	/*
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index 9bc4784..d5a12d9 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -2022,6 +2022,12 @@ int pci_bus_update_busn_res_end(struct pci_bus *b, int bus_max)
>  	return ret;
>  }
>  
> +static void pci_host_update_busn_res_end(
> +		struct pci_host_bridge *host, int max)
> +{
> +	host->busn_res.end = max;
> +}
> +
>  void pci_bus_release_busn_res(struct pci_bus *b)
>  {
>  	struct resource *res = &b->busn_res;
> @@ -2040,32 +2046,20 @@ static struct pci_bus *__pci_scan_root_bus(int bus,
>  		struct pci_host_bridge *host, struct pci_ops *ops,
>  		void *sysdata)
>  {
> -	struct resource_entry *window;
> -	bool found = false;
>  	struct pci_bus *b;
>  	int max;
>  
> -	resource_list_for_each_entry(window, &host->windows)
> -		if (window->res->flags & IORESOURCE_BUS) {
> -			found = true;
> -			break;
> -		}
> -
>  	b = __pci_create_root_bus(bus, host, ops, sysdata);
>  	if (!b)
>  		return NULL;
>  
> -	if (!found) {
> -		dev_info(&b->dev,
> -		 "No busn resource found for root bus, will use [bus %02x-ff]\n",
> -			bus);
> -		pci_bus_insert_busn_res(b, bus, 255);
> -	}
> -
>  	max = pci_scan_child_bus(b);
>  
> -	if (!found)
> +	/* If default busn resource used, update the max bus number */
> +	if (host->busn_res.flags & IORESOURCE_BUS) {
> +		pci_host_update_busn_res_end(host, max);
>  		pci_bus_update_busn_res_end(b, max);
> +	}
>  
>  	return b;
>  }
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 1542df8..f189dfb 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -404,6 +404,8 @@ struct pci_host_bridge {
>  	int domain;
>  	struct device dev;
>  	struct pci_bus *bus;		/* root bus */
> +	/* we use default bus resource if no bus resource provided */
> +	struct resource busn_res;

I don't understand the need for another busn_res here.  The host bridge bus
range should be identical to the root bus range.  Having two copies will
confuse things.

And apparently this host->busn_res is only filled in if the arch doesn't
provide a busn resource?

To check for conflicts between host bridges, can you iterate through the
existing ones and check the range of their root buses?

>  	struct list_head windows;	/* resource_entry */
>  	void (*release_fn)(struct pci_host_bridge *);
>  	void *release_data;
> -- 
> 1.7.1
> 
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