Re: [PATCH 1/3] [RFC] pci: add new method for register PCI hosts

Tomasz Nowicki
2016-05-02T07:35:58Z

On 04/30/2016 01:01 AM, Arnd Bergmann wrote:
> This patch makes the existing 'pci_host_bridge' structure a proper device
> that is usable by PCI host drivers in a more standard way. In addition
> to the existing pci_scan_bus, pci_scan_root_bus, pci_scan_root_bus_msi,
> and pci_create_root_bus interfaces, this unfortunately means having to
> add yet another interface doing basically the same thing, and add some
> extra code in the initial step.
>
> However, this time it's more likely to be extensible enough that we
> won't have to do another one again in the future, and we should be
> able to reduce code much more as a result.
>
> The main idea is to pull the allocation of 'struct pci_host_bridge' out
> of the registration, and let individual host drivers and architecture
> code fill the members before calling the registration function.
>
> There are a number of things we can do based on this:
>
> * Use a single memory allocation for the driver-specific structure
> and the generic PCI host bridge
> * consolidate the contents of driver specific structures by moving
> them into pci_host_bridge
> * Add a consistent interface for removing a PCI host bridge again
> when unloading a host driver module
> * Replace the architecture specific __weak pcibios_* functions with
> callbacks in a pci_host_bridge device
> * Move common boilerplate code from host drivers into the generic
> function, based on contents of the structure
> * Extend pci_host_bridge with additional members when needed without
> having to add arguments to pci_scan_*.
> * Move members of struct pci_bus into pci_host_bridge to avoid
> having lots of identical copies.
>
> As mentioned in a previous email, one open question is whether we want
> to export a function for allocating a pci_host_bridge device in
> combination with the per-device structure or let the driver itself
> call kzalloc.
>
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
> ---
> drivers/pci/probe.c | 100 ++++++++++++++++++++++++++++++----------------------
> include/linux/pci.h | 7 +++-
> 2 files changed, 63 insertions(+), 44 deletions(-)
>
> diff --git a/drivers/pci/probe.c b/drivers/pci/probe.c
> index ae7daeb83e21..fe9d9221b11e 100644
> --- a/drivers/pci/probe.c
> +++ b/drivers/pci/probe.c
> @@ -520,19 +520,6 @@ static void pci_release_host_bridge_dev(struct device *dev)
> kfree(bridge);
> }
>
> -static struct pci_host_bridge *pci_alloc_host_bridge(struct pci_bus *b)
> -{
> - struct pci_host_bridge *bridge;
> -
> - bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
> - if (!bridge)
> - return NULL;
> -
> - INIT_LIST_HEAD(&bridge->windows);
> - bridge->bus = b;
> - return bridge;
> -}
> -
> static const unsigned char pcix_bus_speed[] = {
> PCI_SPEED_UNKNOWN, /* 0 */
> PCI_SPEED_66MHz_PCIX, /* 1 */
> @@ -2108,51 +2095,47 @@ void __weak pcibios_remove_bus(struct pci_bus *bus)
> {
> }
>
> -struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> - struct pci_ops *ops, void *sysdata, struct list_head *resources)
> +int pci_register_host(struct pci_host_bridge *bridge)
> {
> int error;
> - struct pci_host_bridge *bridge;
> struct pci_bus *b, *b2;
> struct resource_entry *window, *n;
> + LIST_HEAD(resources);
> struct resource *res;
> resource_size_t offset;
> char bus_addr[64];
> char *fmt;
> + struct device *parent = bridge->dev.parent;
>
> b = pci_alloc_bus(NULL);
> if (!b)
> - return NULL;
> + return -ENOMEM;
> + bridge->bus = b;
>
> - b->sysdata = sysdata;
> - b->ops = ops;
> - b->number = b->busn_res.start = bus;
> + /* temporarily move resources off the list */
> + list_splice_init(&bridge->windows, &resources);
> + b->sysdata = bridge->sysdata;
> + b->msi = bridge->msi;
> + b->ops = bridge->ops;
> + b->number = b->busn_res.start = bridge->busnr;
> pci_bus_assign_domain_nr(b, parent);

Have you considered to move domain assigning out of here? Domain is
common for every bus under host bridge, hence it could go into the
pci_host_bridge structure. Then I would vote for extra host bridge
allocation call which would assign standard things like this.

> - b2 = pci_find_bus(pci_domain_nr(b), bus);
> + b2 = pci_find_bus(pci_domain_nr(b), bridge->busnr);
> if (b2) {
> /* If we already got to this bus through a different bridge, ignore it */
> dev_dbg(&b2->dev, "bus already known\n");
> + error = -EEXIST;
> goto err_out;
> }
>
> - bridge = pci_alloc_host_bridge(b);
> - if (!bridge)
> - goto err_out;
> -
> - bridge->dev.parent = parent;
> - bridge->dev.release = pci_release_host_bridge_dev;
> - dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bus);
> + dev_set_name(&bridge->dev, "pci%04x:%02x", pci_domain_nr(b), bridge->busnr);
> error = pcibios_root_bridge_prepare(bridge);
> - if (error) {
> - kfree(bridge);
> + if (error)
> goto err_out;
> - }
>
> error = device_register(&bridge->dev);
> - if (error) {
> + if (error)
> put_device(&bridge->dev);
> - goto err_out;
> - }
> +
> b->bridge = get_device(&bridge->dev);
> device_enable_async_suspend(b->bridge);
> pci_set_bus_of_node(b);
> @@ -2163,7 +2146,7 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
>
> b->dev.class = &pcibus_class;
> b->dev.parent = b->bridge;
> - dev_set_name(&b->dev, "%04x:%02x", pci_domain_nr(b), bus);
> + dev_set_name(&b->dev, "%04x:%02x", pci_domain_nr(b), bridge->busnr);
> error = device_register(&b->dev);
> if (error)
> goto class_dev_reg_err;
> @@ -2179,12 +2162,12 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> printk(KERN_INFO "PCI host bridge to bus %s\n", dev_name(&b->dev));
>
> /* Add initial resources to the bus */
> - resource_list_for_each_entry_safe(window, n, resources) {
> + resource_list_for_each_entry_safe(window, n, &resources) {
> list_move_tail(&window->node, &bridge->windows);
> res = window->res;
> offset = window->offset;
> if (res->flags & IORESOURCE_BUS)
> - pci_bus_insert_busn_res(b, bus, res->end);
> + pci_bus_insert_busn_res(b, bridge->busnr, res->end);
> else
> pci_bus_add_resource(b, res, 0);
> if (offset) {
> @@ -2204,16 +2187,16 @@ struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> list_add_tail(&b->node, &pci_root_buses);
> up_write(&pci_bus_sem);
>
> - return b;
> + return 0;
>
> class_dev_reg_err:
> put_device(&bridge->dev);
> device_unregister(&bridge->dev);
> err_out:
> kfree(b);
> - return NULL;
> + return error;
> }
> -EXPORT_SYMBOL_GPL(pci_create_root_bus);
> +EXPORT_SYMBOL_GPL(pci_register_host);
>
> int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int bus_max)
> {
> @@ -2278,6 +2261,39 @@ void pci_bus_release_busn_res(struct pci_bus *b)
> res, ret ? "can not be" : "is");
> }
>
> +static struct pci_bus * pci_create_root_bus_msi(struct device *parent,
> + int bus, struct pci_ops *ops, void *sysdata,
> + struct list_head *resources, struct msi_controller *msi)
> +{
> + struct pci_host_bridge *bridge = kzalloc(sizeof(*bridge), GFP_KERNEL);
> + int ret;
> +
> + if (!bridge)
> + return NULL;
> +
> + bridge->dev.parent = parent;
> + bridge->dev.release = pci_release_host_bridge_dev;
> + bridge->busnr = bus;
> + bridge->ops = ops;
> + bridge->sysdata = sysdata;
> + bridge->msi = msi;
> + list_splice_init(resources, &bridge->windows);
> +
> + ret = pci_register_host(bridge);
> + if (ret)
> + return NULL;
> +
> + return bridge->bus;
> +}
> +
> +struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> + struct pci_ops *ops, void *sysdata, struct list_head *resources)
> +{
> + return pci_create_root_bus_msi(parent, bus, ops, sysdata, resources,
> + NULL);
> +}
> +EXPORT_SYMBOL_GPL(pci_create_root_bus);
> +
> struct pci_bus *pci_scan_root_bus_msi(struct device *parent, int bus,
> struct pci_ops *ops, void *sysdata,
> struct list_head *resources, struct msi_controller *msi)
> @@ -2293,12 +2309,10 @@ struct pci_bus *pci_scan_root_bus_msi(struct device *parent, int bus,
> break;
> }
>
> - b = pci_create_root_bus(parent, bus, ops, sysdata, resources);
> + b = pci_create_root_bus_msi(parent, bus, ops, sysdata, resources, msi);
> if (!b)
> return NULL;
>
> - b->msi = msi;
> -
> if (!found) {
> dev_info(&b->dev,
> "No busn resource found for root bus, will use [bus %02x-ff]\n",
> diff --git a/include/linux/pci.h b/include/linux/pci.h
> index 81f070a47ee7..8bb5dff617a1 100644
> --- a/include/linux/pci.h
> +++ b/include/linux/pci.h
> @@ -400,10 +400,14 @@ static inline int pci_channel_offline(struct pci_dev *pdev)
>
> struct pci_host_bridge {
> struct device dev;
> - struct pci_bus *bus; /* root bus */
> + struct pci_ops *ops;
> + void *sysdata;
> + int busnr;
> + struct pci_bus *bus; /* points to root */
> struct list_head windows; /* resource_entry */
> void (*release_fn)(struct pci_host_bridge *);
> void *release_data;
> + struct msi_controller *msi;
> unsigned int ignore_reset_delay:1; /* for entire hierarchy */
> /* Resource alignment requirements */
> resource_size_t (*align_resource)(struct pci_dev *dev,
> @@ -812,6 +816,7 @@ struct pci_bus *pci_scan_bus(int bus, struct pci_ops *ops, void *sysdata);
> struct pci_bus *pci_create_root_bus(struct device *parent, int bus,
> struct pci_ops *ops, void *sysdata,
> struct list_head *resources);
> +int pci_register_host(struct pci_host_bridge *bridge);
> int pci_bus_insert_busn_res(struct pci_bus *b, int bus, int busmax);
> int pci_bus_update_busn_res_end(struct pci_bus *b, int busmax);
> void pci_bus_release_busn_res(struct pci_bus *b);