From 2fa39159b6a9931d6fd82ecbe65357e0ad77e1a4 Mon Sep 17 00:00:00 2001 From: Shawn Lin Date: Mon, 14 Nov 2016 15:20:57 -0600 Subject: [PATCH 1/2] Documentation/devicetree: Add PCIe max-link-speed property Some of the host drivers have the requirement of knowing whether the EP would never train at some link speed at all. For instance, on some boards, the link won't train at 5 GT/s but the host driver still sacrifice some cycles to wait for the result of training at 5 GT/s as the host could actually support 5 GT/s. So we could parse this new property and make the host drivers be aware of these cases. Signed-off-by: Shawn Lin Signed-off-by: Bjorn Helgaas Acked-by: Rob Herring --- Documentation/devicetree/bindings/pci/pci.txt | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Documentation/devicetree/bindings/pci/pci.txt b/Documentation/devicetree/bindings/pci/pci.txt index 08dcfad09f8d..50f9e2ca5b13 100644 --- a/Documentation/devicetree/bindings/pci/pci.txt +++ b/Documentation/devicetree/bindings/pci/pci.txt @@ -18,3 +18,9 @@ driver implementation may support the following properties: host bridges in the system, otherwise potentially conflicting domain numbers may be assigned to root buses behind different host bridges. The domain number for each host bridge in the system must be unique. +- max-link-speed: + If present this property specifies PCI gen for link capability. Host + drivers could add this as a strategy to avoid unnecessary operation for + unsupported link speed, for instance, trying to do training for + unsupported link speed, etc. Must be '4' for gen4, '3' for gen3, '2' + for gen2, and '1' for gen1. Any other values are invalid. From 9a1dc3891255afd836f355b117fd6b975d0b1eb2 Mon Sep 17 00:00:00 2001 From: Shawn Lin Date: Mon, 14 Nov 2016 15:21:14 -0600 Subject: [PATCH 2/2] of/pci: Add of_pci_get_max_link_speed() to parse max-link-speed from DT This new helper function could be used by host drivers to get the limitaion of max link speed provided by DT. If the property isn't assigned or is invalid, it will return -EINVAL to the caller. Signed-off-by: Shawn Lin Signed-off-by: Bjorn Helgaas Acked-by: Rob Herring --- drivers/of/of_pci.c | 21 +++++++++++++++++++++ include/linux/of_pci.h | 7 +++++++ 2 files changed, 28 insertions(+) diff --git a/drivers/of/of_pci.c b/drivers/of/of_pci.c index b58be12ab277..0ee42c3e66a1 100644 --- a/drivers/of/of_pci.c +++ b/drivers/of/of_pci.c @@ -119,6 +119,27 @@ int of_get_pci_domain_nr(struct device_node *node) } EXPORT_SYMBOL_GPL(of_get_pci_domain_nr); +/** + * This function will try to find the limitation of link speed by finding + * a property called "max-link-speed" of the given device node. + * + * @node: device tree node with the max link speed information + * + * Returns the associated max link speed from DT, or a negative value if the + * required property is not found or is invalid. + */ +int of_pci_get_max_link_speed(struct device_node *node) +{ + u32 max_link_speed; + + if (of_property_read_u32(node, "max-link-speed", &max_link_speed) || + max_link_speed > 4) + return -EINVAL; + + return max_link_speed; +} +EXPORT_SYMBOL_GPL(of_pci_get_max_link_speed); + /** * of_pci_check_probe_only - Setup probe only mode if linux,pci-probe-only * is present and valid diff --git a/include/linux/of_pci.h b/include/linux/of_pci.h index 7fd5cfce9140..0e0974eceb80 100644 --- a/include/linux/of_pci.h +++ b/include/linux/of_pci.h @@ -16,6 +16,7 @@ int of_pci_get_devfn(struct device_node *np); int of_irq_parse_and_map_pci(const struct pci_dev *dev, u8 slot, u8 pin); int of_pci_parse_bus_range(struct device_node *node, struct resource *res); int of_get_pci_domain_nr(struct device_node *node); +int of_pci_get_max_link_speed(struct device_node *node); void of_pci_check_probe_only(void); int of_pci_map_rid(struct device_node *np, u32 rid, const char *map_name, const char *map_mask_name, @@ -62,6 +63,12 @@ static inline int of_pci_map_rid(struct device_node *np, u32 rid, return -EINVAL; } +static inline int +of_pci_get_max_link_speed(struct device_node *node) +{ + return -EINVAL; +} + static inline void of_pci_check_probe_only(void) { } #endif