diff options
| -rw-r--r-- | drivers/usb/core/hub.c | 211 | ||||
| -rw-r--r-- | include/linux/usb.h | 37 |
2 files changed, 247 insertions, 1 deletions
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index 100e08f8a027..5219507bf227 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -189,9 +189,216 @@ static int usb_device_supports_lpm(struct usb_device *udev) return 1; return 0; } + + /* All USB 3.0 must support LPM, but we need their max exit latency + * information from the SuperSpeed Extended Capabilities BOS descriptor. + */ + if (!udev->bos->ss_cap) { + dev_warn(&udev->dev, "No LPM exit latency info found. " + "Power management will be impacted.\n"); + return 0; + } + if (udev->parent->lpm_capable) + return 1; + + dev_warn(&udev->dev, "Parent hub missing LPM exit latency info. " + "Power management will be impacted.\n"); return 0; } +/* + * Set the Maximum Exit Latency (MEL) for the host to initiate a transition from + * either U1 or U2. + */ +static void usb_set_lpm_mel(struct usb_device *udev, + struct usb3_lpm_parameters *udev_lpm_params, + unsigned int udev_exit_latency, + struct usb_hub *hub, + struct usb3_lpm_parameters *hub_lpm_params, + unsigned int hub_exit_latency) +{ + unsigned int total_mel; + unsigned int device_mel; + unsigned int hub_mel; + + /* + * Calculate the time it takes to transition all links from the roothub + * to the parent hub into U0. The parent hub must then decode the + * packet (hub header decode latency) to figure out which port it was + * bound for. + * + * The Hub Header decode latency is expressed in 0.1us intervals (0x1 + * means 0.1us). Multiply that by 100 to get nanoseconds. + */ + total_mel = hub_lpm_params->mel + + (hub->descriptor->u.ss.bHubHdrDecLat * 100); + + /* + * How long will it take to transition the downstream hub's port into + * U0? The greater of either the hub exit latency or the device exit + * latency. + * + * The BOS U1/U2 exit latencies are expressed in 1us intervals. + * Multiply that by 1000 to get nanoseconds. + */ + device_mel = udev_exit_latency * 1000; + hub_mel = hub_exit_latency * 1000; + if (device_mel > hub_mel) + total_mel += device_mel; + else + total_mel += hub_mel; + + udev_lpm_params->mel = total_mel; +} + +/* + * Set the maximum Device to Host Exit Latency (PEL) for the device to initiate + * a transition from either U1 or U2. + */ +static void usb_set_lpm_pel(struct usb_device *udev, + struct usb3_lpm_parameters *udev_lpm_params, + unsigned int udev_exit_latency, + struct usb_hub *hub, + struct usb3_lpm_parameters *hub_lpm_params, + unsigned int hub_exit_latency, + unsigned int port_to_port_exit_latency) +{ + unsigned int first_link_pel; + unsigned int hub_pel; + + /* + * First, the device sends an LFPS to transition the link between the + * device and the parent hub into U0. The exit latency is the bigger of + * the device exit latency or the hub exit latency. + */ + if (udev_exit_latency > hub_exit_latency) + first_link_pel = udev_exit_latency * 1000; + else + first_link_pel = hub_exit_latency * 1000; + + /* + * When the hub starts to receive the LFPS, there is a slight delay for + * it to figure out that one of the ports is sending an LFPS. Then it + * will forward the LFPS to its upstream link. The exit latency is the + * delay, plus the PEL that we calculated for this hub. + */ + hub_pel = port_to_port_exit_latency * 1000 + hub_lpm_params->pel; + + /* + * According to figure C-7 in the USB 3.0 spec, the PEL for this device + * is the greater of the two exit latencies. + */ + if (first_link_pel > hub_pel) + udev_lpm_params->pel = first_link_pel; + else + udev_lpm_params->pel = hub_pel; +} + +/* + * Set the System Exit Latency (SEL) to indicate the total worst-case time from + * when a device initiates a transition to U0, until when it will receive the + * first packet from the host controller. + * + * Section C.1.5.1 describes the four components to this: + * - t1: device PEL + * - t2: time for the ERDY to make it from the device to the host. + * - t3: a host-specific delay to process the ERDY. + * - t4: time for the packet to make it from the host to the device. + * + * t3 is specific to both the xHCI host and the platform the host is integrated + * into. The Intel HW folks have said it's negligible, FIXME if a different + * vendor says otherwise. + */ +static void usb_set_lpm_sel(struct usb_device *udev, + struct usb3_lpm_parameters *udev_lpm_params) +{ + struct usb_device *parent; + unsigned int num_hubs; + unsigned int total_sel; + + /* t1 = device PEL */ + total_sel = udev_lpm_params->pel; + /* How many external hubs are in between the device & the root port. */ + for (parent = udev->parent, num_hubs = 0; parent->parent; + parent = parent->parent) + num_hubs++; + /* t2 = 2.1us + 250ns * (num_hubs - 1) */ + if (num_hubs > 0) + total_sel += 2100 + 250 * (num_hubs - 1); + + /* t4 = 250ns * num_hubs */ + total_sel += 250 * num_hubs; + + udev_lpm_params->sel = total_sel; +} + +static void usb_set_lpm_parameters(struct usb_device *udev) +{ + struct usb_hub *hub; + unsigned int port_to_port_delay; + unsigned int udev_u1_del; + unsigned int udev_u2_del; + unsigned int hub_u1_del; + unsigned int hub_u2_del; + + if (!udev->lpm_capable || udev->speed != USB_SPEED_SUPER) + return; + + hub = hdev_to_hub(udev->parent); + /* It doesn't take time to transition the roothub into U0, since it + * doesn't have an upstream link. + */ + if (!hub) + return; + + udev_u1_del = udev->bos->ss_cap->bU1devExitLat; + udev_u2_del = udev->bos->ss_cap->bU2DevExitLat; + hub_u1_del = udev->parent->bos->ss_cap->bU1devExitLat; + hub_u2_del = udev->parent->bos->ss_cap->bU2DevExitLat; + + usb_set_lpm_mel(udev, &udev->u1_params, udev_u1_del, + hub, &udev->parent->u1_params, hub_u1_del); + + usb_set_lpm_mel(udev, &udev->u2_params, udev_u2_del, + hub, &udev->parent->u2_params, hub_u2_del); + + /* + * Appendix C, section C.2.2.2, says that there is a slight delay from + * when the parent hub notices the downstream port is trying to + * transition to U0 to when the hub initiates a U0 transition on its + * upstream port. The section says the delays are tPort2PortU1EL and + * tPort2PortU2EL, but it doesn't define what they are. + * + * The hub chapter, sections 10.4.2.4 and 10.4.2.5 seem to be talking + * about the same delays. Use the maximum delay calculations from those + * sections. For U1, it's tHubPort2PortExitLat, which is 1us max. For + * U2, it's tHubPort2PortExitLat + U2DevExitLat - U1DevExitLat. I + * assume the device exit latencies they are talking about are the hub + * exit latencies. + * + * What do we do if the U2 exit latency is less than the U1 exit + * latency? It's possible, although not likely... + */ + port_to_port_delay = 1; + + usb_set_lpm_pel(udev, &udev->u1_params, udev_u1_del, + hub, &udev->parent->u1_params, hub_u1_del, + port_to_port_delay); + + if (hub_u2_del > hub_u1_del) + port_to_port_delay = 1 + hub_u2_del - hub_u1_del; + else + port_to_port_delay = 1 + hub_u1_del; + + usb_set_lpm_pel(udev, &udev->u2_params, udev_u2_del, + hub, &udev->parent->u2_params, hub_u2_del, + port_to_port_delay); + + /* Now that we've got PEL, calculate SEL. */ + usb_set_lpm_sel(udev, &udev->u1_params); + usb_set_lpm_sel(udev, &udev->u2_params); +} + /* USB 2.0 spec Section 11.24.4.5 */ static int get_hub_descriptor(struct usb_device *hdev, void *data) { @@ -3226,8 +3433,10 @@ hub_port_init (struct usb_hub *hub, struct usb_device *udev, int port1, if (udev->wusb == 0 && le16_to_cpu(udev->descriptor.bcdUSB) >= 0x0201) { retval = usb_get_bos_descriptor(udev); - if (!retval) + if (!retval) { udev->lpm_capable = usb_device_supports_lpm(udev); + usb_set_lpm_parameters(udev); + } } retval = 0; diff --git a/include/linux/usb.h b/include/linux/usb.h index 14933451d21d..e6c815590fdd 100644 --- a/include/linux/usb.h +++ b/include/linux/usb.h @@ -378,6 +378,39 @@ enum usb_device_removable { USB_DEVICE_FIXED, }; +/* + * USB 3.0 Link Power Management (LPM) parameters. + * + * PEL and SEL are USB 3.0 Link PM latencies for device-initiated LPM exit. + * MEL is the USB 3.0 Link PM latency for host-initiated LPM exit. + * All three are stored in nanoseconds. + */ +struct usb3_lpm_parameters { + /* + * Maximum exit latency (MEL) for the host to send a packet to the + * device (either a Ping for isoc endpoints, or a data packet for + * interrupt endpoints), the hubs to decode the packet, and for all hubs + * in the path to transition the links to U0. + */ + unsigned int mel; + /* + * Maximum exit latency for a device-initiated LPM transition to bring + * all links into U0. Abbreviated as "PEL" in section 9.4.12 of the USB + * 3.0 spec, with no explanation of what "P" stands for. "Path"? + */ + unsigned int pel; + + /* + * The System Exit Latency (SEL) includes PEL, and three other + * latencies. After a device initiates a U0 transition, it will take + * some time from when the device sends the ERDY to when it will finally + * receive the data packet. Basically, SEL should be the worse-case + * latency from when a device starts initiating a U0 transition to when + * it will get data. + */ + unsigned int sel; +}; + /** * struct usb_device - kernel's representation of a USB device * @devnum: device number; address on a USB bus @@ -435,6 +468,8 @@ enum usb_device_removable { * specific data for the device. * @slot_id: Slot ID assigned by xHCI * @removable: Device can be physically removed from this port + * @u1_params: exit latencies for U1 (USB 3.0 LPM). + * @u2_params: exit latencies for U2 (USB 3.0 LPM). * * Notes: * Usbcore drivers should not set usbdev->state directly. Instead use @@ -507,6 +542,8 @@ struct usb_device { struct wusb_dev *wusb_dev; int slot_id; enum usb_device_removable removable; + struct usb3_lpm_parameters u1_params; + struct usb3_lpm_parameters u2_params; }; #define to_usb_device(d) container_of(d, struct usb_device, dev) |