This is a note to let you know that I've just added the patch titled
usb: hub: Disable USB 3 device initiated lpm if exit latency is too
to my usb git tree which can be found at git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/usb.git in the usb-linus branch.
The patch will show up in the next release of the linux-next tree (usually sometime within the next 24 hours during the week.)
The patch will hopefully also be merged in Linus's tree for the next -rc kernel release.
If you have any questions about this process, please let me know.
From 1b7f56fbc7a1b66967b6114d1b5f5a257c3abae6 Mon Sep 17 00:00:00 2001
From: Mathias Nyman mathias.nyman@linux.intel.com Date: Thu, 15 Jul 2021 18:01:22 +0300 Subject: usb: hub: Disable USB 3 device initiated lpm if exit latency is too high
The device initiated link power management U1/U2 states should not be enabled in case the system exit latency plus one bus interval (125us) is greater than the shortest service interval of any periodic endpoint.
This is the case for both U1 and U2 sytstem exit latencies and link states.
See USB 3.2 section 9.4.9 "Set Feature" for more details
Note, before this patch the host and device initiated U1/U2 lpm states were both enabled with lpm. After this patch it's possible to end up with only host inititated U1/U2 lpm in case the exit latencies won't allow device initiated lpm.
If this case we still want to set the udev->usb3_lpm_ux_enabled flag so that sysfs users can see the link may go to U1/U2.
Signed-off-by: Mathias Nyman mathias.nyman@linux.intel.com Cc: stable stable@vger.kernel.org Link: https://lore.kernel.org/r/20210715150122.1995966-2-mathias.nyman@linux.intel... Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/core/hub.c | 68 ++++++++++++++++++++++++++++++++++-------- 1 file changed, 56 insertions(+), 12 deletions(-)
diff --git a/drivers/usb/core/hub.c b/drivers/usb/core/hub.c index a35d0bedafa3..86658a81d284 100644 --- a/drivers/usb/core/hub.c +++ b/drivers/usb/core/hub.c @@ -4116,6 +4116,47 @@ static int usb_set_lpm_timeout(struct usb_device *udev, return 0; }
+/* + * Don't allow device intiated U1/U2 if the system exit latency + one bus + * interval is greater than the minimum service interval of any active + * periodic endpoint. See USB 3.2 section 9.4.9 + */ +static bool usb_device_may_initiate_lpm(struct usb_device *udev, + enum usb3_link_state state) +{ + unsigned int sel; /* us */ + int i, j; + + if (state == USB3_LPM_U1) + sel = DIV_ROUND_UP(udev->u1_params.sel, 1000); + else if (state == USB3_LPM_U2) + sel = DIV_ROUND_UP(udev->u2_params.sel, 1000); + else + return false; + + for (i = 0; i < udev->actconfig->desc.bNumInterfaces; i++) { + struct usb_interface *intf; + struct usb_endpoint_descriptor *desc; + unsigned int interval; + + intf = udev->actconfig->interface[i]; + if (!intf) + continue; + + for (j = 0; j < intf->cur_altsetting->desc.bNumEndpoints; j++) { + desc = &intf->cur_altsetting->endpoint[j].desc; + + if (usb_endpoint_xfer_int(desc) || + usb_endpoint_xfer_isoc(desc)) { + interval = (1 << (desc->bInterval - 1)) * 125; + if (sel + 125 > interval) + return false; + } + } + } + return true; +} + /* * Enable the hub-initiated U1/U2 idle timeouts, and enable device-initiated * U1/U2 entry. @@ -4188,20 +4229,23 @@ static void usb_enable_link_state(struct usb_hcd *hcd, struct usb_device *udev, * U1/U2_ENABLE */ if (udev->actconfig && - usb_set_device_initiated_lpm(udev, state, true) == 0) { - if (state == USB3_LPM_U1) - udev->usb3_lpm_u1_enabled = 1; - else if (state == USB3_LPM_U2) - udev->usb3_lpm_u2_enabled = 1; - } else { - /* Don't request U1/U2 entry if the device - * cannot transition to U1/U2. - */ - usb_set_lpm_timeout(udev, state, 0); - hcd->driver->disable_usb3_lpm_timeout(hcd, udev, state); + usb_device_may_initiate_lpm(udev, state)) { + if (usb_set_device_initiated_lpm(udev, state, true)) { + /* + * Request to enable device initiated U1/U2 failed, + * better to turn off lpm in this case. + */ + usb_set_lpm_timeout(udev, state, 0); + hcd->driver->disable_usb3_lpm_timeout(hcd, udev, state); + return; + } } -}
+ if (state == USB3_LPM_U1) + udev->usb3_lpm_u1_enabled = 1; + else if (state == USB3_LPM_U2) + udev->usb3_lpm_u2_enabled = 1; +} /* * Disable the hub-initiated U1/U2 idle timeouts, and disable device-initiated * U1/U2 entry.