diff options
| -rw-r--r-- | drivers/pci/p2pdma.c | 73 |
1 files changed, 38 insertions, 35 deletions
diff --git a/drivers/pci/p2pdma.c b/drivers/pci/p2pdma.c index 196382630363..a860137fac89 100644 --- a/drivers/pci/p2pdma.c +++ b/drivers/pci/p2pdma.c @@ -354,7 +354,7 @@ static bool host_bridge_whitelist(struct pci_dev *a, struct pci_dev *b) } static enum pci_p2pdma_map_type -__upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client, +__calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, int *dist, bool *acs_redirects, struct seq_buf *acs_list) { struct pci_dev *a = provider, *b = client, *bb; @@ -433,52 +433,55 @@ static unsigned long map_types_idx(struct pci_dev *client) } /* - * Find the distance through the nearest common upstream bridge between - * two PCI devices. + * Calculate the P2PDMA mapping type and distance between two PCI devices. * - * If the two devices are the same device then 0 will be returned. + * If the two devices are the same PCI function, return + * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 0. * - * If there are two virtual functions of the same device behind the same - * bridge port then 2 will be returned (one step down to the PCIe switch, - * then one step back to the same device). + * If they are two functions of the same device, return + * PCI_P2PDMA_MAP_BUS_ADDR and a distance of 2 (one hop up to the bridge, + * then one hop back down to another function of the same device). * - * In the case where two devices are connected to the same PCIe switch, the - * value 4 will be returned. This corresponds to the following PCI tree: + * In the case where two devices are connected to the same PCIe switch, + * return a distance of 4. This corresponds to the following PCI tree: * * -+ Root Port * \+ Switch Upstream Port - * +-+ Switch Downstream Port + * +-+ Switch Downstream Port 0 * + \- Device A - * \-+ Switch Downstream Port + * \-+ Switch Downstream Port 1 * \- Device B * - * The distance is 4 because we traverse from Device A through the downstream - * port of the switch, to the common upstream port, back up to the second - * downstream port and then to Device B. + * The distance is 4 because we traverse from Device A to Downstream Port 0 + * to the common Switch Upstream Port, back down to Downstream Port 1 and + * then to Device B. The mapping type returned depends on the ACS + * redirection setting of the ports along the path. * - * Any two devices that cannot communicate using p2pdma will return - * PCI_P2PDMA_MAP_NOT_SUPPORTED. + * If ACS redirect is set on any port in the path, traffic between the + * devices will go through the host bridge, so return + * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE; otherwise return + * PCI_P2PDMA_MAP_BUS_ADDR. * * Any two devices that have a data path that goes through the host bridge - * will consult a whitelist. If the host bridges are on the whitelist, - * this function will return PCI_P2PDMA_MAP_THRU_HOST_BRIDGE. - * - * If either bridge is not on the whitelist this function returns + * will consult a whitelist. If the host bridge is in the whitelist, return + * PCI_P2PDMA_MAP_THRU_HOST_BRIDGE with the distance set to the number of + * ports per above. If the device is not in the whitelist, return * PCI_P2PDMA_MAP_NOT_SUPPORTED. * - * If a bridge which has any ACS redirection bits set is in the path, - * acs_redirects will be set to true. In this case, a list of all infringing - * bridge addresses will be populated in acs_list (assuming it's non-null) - * for printk purposes. + * If any ACS redirect bits are set, then acs_redirects boolean will be set + * to true and their PCI device names will be appended to the acs_list + * seq_buf. This seq_buf is used to print a warning informing the user how + * to disable ACS using a command line parameter. (See + * calc_map_type_and_dist_warn() below) */ static enum pci_p2pdma_map_type -upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client, +calc_map_type_and_dist(struct pci_dev *provider, struct pci_dev *client, int *dist, bool *acs_redirects, struct seq_buf *acs_list) { enum pci_p2pdma_map_type map_type; - map_type = __upstream_bridge_distance(provider, client, dist, - acs_redirects, acs_list); + map_type = __calc_map_type_and_dist(provider, client, dist, + acs_redirects, acs_list); if (map_type == PCI_P2PDMA_MAP_THRU_HOST_BRIDGE) { if (!cpu_supports_p2pdma() && @@ -494,8 +497,8 @@ upstream_bridge_distance(struct pci_dev *provider, struct pci_dev *client, } static enum pci_p2pdma_map_type -upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client, - int *dist) +calc_map_type_and_dist_warn(struct pci_dev *provider, struct pci_dev *client, + int *dist) { struct seq_buf acs_list; bool acs_redirects; @@ -505,8 +508,8 @@ upstream_bridge_distance_warn(struct pci_dev *provider, struct pci_dev *client, if (!acs_list.buffer) return -ENOMEM; - ret = upstream_bridge_distance(provider, client, dist, &acs_redirects, - &acs_list); + ret = calc_map_type_and_dist(provider, client, dist, &acs_redirects, + &acs_list); if (acs_redirects) { pci_warn(client, "ACS redirect is set between the client and provider (%s)\n", pci_name(provider)); @@ -565,11 +568,11 @@ int pci_p2pdma_distance_many(struct pci_dev *provider, struct device **clients, } if (verbose) - ret = upstream_bridge_distance_warn(provider, - pci_client, &distance); + ret = calc_map_type_and_dist_warn(provider, pci_client, + &distance); else - ret = upstream_bridge_distance(provider, pci_client, - &distance, NULL, NULL); + ret = calc_map_type_and_dist(provider, pci_client, + &distance, NULL, NULL); pci_dev_put(pci_client); |