| Message ID | 20230901001518.25403-1-quic_wcheng@quicinc.com (mailing list archive) |
|---|---|
| State | Superseded |
| Headers | show |
| Series | [v2] usb: host: xhci: Avoid XHCI resume delay if SSUSB device is not present | expand |
On 1.9.2023 3.15, Wesley Cheng wrote: > There is a 120ms delay implemented for allowing the XHCI host controller to > detect a U3 wakeup pulse. The intention is to wait for the device to retry > the wakeup event if the USB3 PORTSC doesn't reflect the RESUME link status > by the time it is checked. As per the USB3 specification: > > tU3WakeupRetryDelay ("Table 7-12. LTSSM State Transition Timeouts") > > This would allow the XHCI resume sequence to determine if the root hub > needs to be also resumed. However, in case there is no device connected, > or if there is only a HSUSB device connected, this delay would still affect > the overall resume timing. > > Since this delay is solely for detecting U3 wake events (USB3 specific) > then ignore this delay for the disconnected case and the HSUSB connected > only case. Thanks, makes sense > > Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com> > --- > drivers/usb/host/xhci.c | 26 +++++++++++++++++++++++++- > 1 file changed, 25 insertions(+), 1 deletion(-) > > diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c > index e1b1b64a0723..640db6a4e686 100644 > --- a/drivers/usb/host/xhci.c > +++ b/drivers/usb/host/xhci.c > @@ -805,6 +805,24 @@ static void xhci_disable_hub_port_wake(struct xhci_hcd *xhci, > spin_unlock_irqrestore(&xhci->lock, flags); > } > > +static bool xhci_usb3_dev_connected(struct xhci_hcd *xhci) > +{ > + struct xhci_port **ports; > + int port_index; > + u32 portsc; > + > + port_index = xhci->usb3_rhub.num_ports; > + ports = xhci->usb3_rhub.ports; > + > + while (port_index--) { > + portsc = readl(ports[port_index]->addr); > + if (portsc & (portsc & PORT_CONNECT)) > + return true; > + } > + > + return false; > +} > + This is one way, but we can probably avoid re-reading all the usb3 portsc registers by checking if any bit is set in either: // bitfield, set if xhci usb3 port neatly set to U3 with a hub request xhci->usb3_rhub.bus_state.suspended_ports // bitfield, set if xhci usb3 port is forced to U3 during xhci suspend. xhci->usb3_rhub.bus_state.bus_suspended But haven't checked this works in all corner cases. Thanks Mathias
Hi Mathias, On 9/11/2023 6:50 AM, Mathias Nyman wrote: > On 1.9.2023 3.15, Wesley Cheng wrote: >> There is a 120ms delay implemented for allowing the XHCI host >> controller to >> detect a U3 wakeup pulse. The intention is to wait for the device to >> retry >> the wakeup event if the USB3 PORTSC doesn't reflect the RESUME link >> status >> by the time it is checked. As per the USB3 specification: >> >> tU3WakeupRetryDelay ("Table 7-12. LTSSM State Transition Timeouts") >> >> This would allow the XHCI resume sequence to determine if the root hub >> needs to be also resumed. However, in case there is no device connected, >> or if there is only a HSUSB device connected, this delay would still >> affect >> the overall resume timing. >> >> Since this delay is solely for detecting U3 wake events (USB3 specific) >> then ignore this delay for the disconnected case and the HSUSB connected >> only case. > > Thanks, makes sense > >> >> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com> >> --- >> drivers/usb/host/xhci.c | 26 +++++++++++++++++++++++++- >> 1 file changed, 25 insertions(+), 1 deletion(-) >> >> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c >> index e1b1b64a0723..640db6a4e686 100644 >> --- a/drivers/usb/host/xhci.c >> +++ b/drivers/usb/host/xhci.c >> @@ -805,6 +805,24 @@ static void xhci_disable_hub_port_wake(struct >> xhci_hcd *xhci, >> spin_unlock_irqrestore(&xhci->lock, flags); >> } >> +static bool xhci_usb3_dev_connected(struct xhci_hcd *xhci) >> +{ >> + struct xhci_port **ports; >> + int port_index; >> + u32 portsc; >> + >> + port_index = xhci->usb3_rhub.num_ports; >> + ports = xhci->usb3_rhub.ports; >> + >> + while (port_index--) { >> + portsc = readl(ports[port_index]->addr); >> + if (portsc & (portsc & PORT_CONNECT)) >> + return true; >> + } >> + >> + return false; >> +} >> + > > This is one way, but we can probably avoid re-reading all the usb3 > portsc registers > by checking if any bit is set in either: > > // bitfield, set if xhci usb3 port neatly set to U3 with a hub request > xhci->usb3_rhub.bus_state.suspended_ports > > // bitfield, set if xhci usb3 port is forced to U3 during xhci suspend. > xhci->usb3_rhub.bus_state.bus_suspended > > But haven't checked this works in all corner cases. > Thanks for the suggestion. I think I also looked at seeing if we could use the suspended_ports param, and it was missing one of the use cases we had. I haven't thought on combining it with the bus_suspend param also to see if it could work. Let me give it a try, and I'll get back to you. Thanks Wesley Cheng
Hi Mathias, On 9/11/2023 5:15 PM, Wesley Cheng wrote: > Hi Mathias, > > On 9/11/2023 6:50 AM, Mathias Nyman wrote: >> On 1.9.2023 3.15, Wesley Cheng wrote: >>> There is a 120ms delay implemented for allowing the XHCI host >>> controller to >>> detect a U3 wakeup pulse. The intention is to wait for the device to >>> retry >>> the wakeup event if the USB3 PORTSC doesn't reflect the RESUME link >>> status >>> by the time it is checked. As per the USB3 specification: >>> >>> tU3WakeupRetryDelay ("Table 7-12. LTSSM State Transition Timeouts") >>> >>> This would allow the XHCI resume sequence to determine if the root hub >>> needs to be also resumed. However, in case there is no device >>> connected, >>> or if there is only a HSUSB device connected, this delay would still >>> affect >>> the overall resume timing. >>> >>> Since this delay is solely for detecting U3 wake events (USB3 specific) >>> then ignore this delay for the disconnected case and the HSUSB connected >>> only case. >> >> Thanks, makes sense >> >>> >>> Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com> >>> --- >>> drivers/usb/host/xhci.c | 26 +++++++++++++++++++++++++- >>> 1 file changed, 25 insertions(+), 1 deletion(-) >>> >>> diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c >>> index e1b1b64a0723..640db6a4e686 100644 >>> --- a/drivers/usb/host/xhci.c >>> +++ b/drivers/usb/host/xhci.c >>> @@ -805,6 +805,24 @@ static void xhci_disable_hub_port_wake(struct >>> xhci_hcd *xhci, >>> spin_unlock_irqrestore(&xhci->lock, flags); >>> } >>> +static bool xhci_usb3_dev_connected(struct xhci_hcd *xhci) >>> +{ >>> + struct xhci_port **ports; >>> + int port_index; >>> + u32 portsc; >>> + >>> + port_index = xhci->usb3_rhub.num_ports; >>> + ports = xhci->usb3_rhub.ports; >>> + >>> + while (port_index--) { >>> + portsc = readl(ports[port_index]->addr); >>> + if (portsc & (portsc & PORT_CONNECT)) >>> + return true; >>> + } >>> + >>> + return false; >>> +} >>> + >> >> This is one way, but we can probably avoid re-reading all the usb3 >> portsc registers >> by checking if any bit is set in either: >> >> // bitfield, set if xhci usb3 port neatly set to U3 with a hub request >> xhci->usb3_rhub.bus_state.suspended_ports >> >> // bitfield, set if xhci usb3 port is forced to U3 during xhci suspend. >> xhci->usb3_rhub.bus_state.bus_suspended >> >> But haven't checked this works in all corner cases. >> > Thanks for the suggestion. I think I also looked at seeing if we could > use the suspended_ports param, and it was missing one of the use cases > we had. I haven't thought on combining it with the bus_suspend param > also to see if it could work. Let me give it a try, and I'll get back > to you. > So in one of our normal use cases, which is to use an USB OTG adapter with our devices, we can have this connected with no device. In this situation, the XHCI HCD and root hub are enumerated, and is in a state where nothing is connected to the port. I added a print to the xhci_resume() path to check the status of "suspended_ports" and "bus_suspended" and they seem to reflect the same status as when there is something connected (to a device that supports autosuspend). Here's some pointers I've found on why these parameters may not work: 1. bus_suspended is only set (for the bus) if we reach the bus_suspend() callback from USB HCD if the link is still in U0. If USB autosuspend is enabled, then the suspending of the root hub udev, would have caused a call to suspend the port (usb_port_suspend()), and that would set "suspended_ports" and placed the link in U3 already. 2. "suspended_ports" can't differentiate if a device is connected or not after plugging in a USB3 device that has autosuspend enabled. It looks like on device disconnection, the suspended_ports isn't cleared for that port number. It is only cleared during the resume path where a get port status is queried: static void xhci_get_usb3_port_status(struct xhci_port *port, u32 *status, u32 portsc) { ... /* USB3 specific wPortStatus bits */ if (portsc & PORT_POWER) { *status |= USB_SS_PORT_STAT_POWER; /* link state handling */ if (link_state == XDEV_U0) bus_state->suspended_ports &= ~(1 << portnum); } IMO, this seems kind of weird, because the PLS shows that the port is in the RxDetect state, so it technically isn't suspended. If you think we should clear suspended_ports on disconnect, then I think we can also change the logic to rely on it for avoiding the unnecessary delay in xhci_resume(). Thanks Wesley Cheng
Hi On 13.9.2023 0.51, Wesley Cheng wrote: > Hi Mathias, > >>> This is one way, but we can probably avoid re-reading all the usb3 portsc registers >>> by checking if any bit is set in either: >>> >>> // bitfield, set if xhci usb3 port neatly set to U3 with a hub request >>> xhci->usb3_rhub.bus_state.suspended_ports >>> >>> // bitfield, set if xhci usb3 port is forced to U3 during xhci suspend. >>> xhci->usb3_rhub.bus_state.bus_suspended >>> >>> But haven't checked this works in all corner cases. >>> >> Thanks for the suggestion. I think I also looked at seeing if we could use the suspended_ports param, and it was missing one of the use cases we had. I haven't thought on combining it with the bus_suspend param also to see if it could work. Let me give it a try, and I'll get back to you. >> > > So in one of our normal use cases, which is to use an USB OTG adapter with our devices, we can have this connected with no device. In this situation, the XHCI HCD and root hub are enumerated, and is in a state where nothing is connected to the port. I added a print to the xhci_resume() path to check the status of "suspended_ports" and "bus_suspended" and they seem to reflect the same status as when there is something connected (to a device that supports autosuspend). Here's some pointers I've found on why these parameters may not work: > > 1. bus_suspended is only set (for the bus) if we reach the bus_suspend() callback from USB HCD if the link is still in U0. If USB autosuspend is enabled, then the suspending of the root hub udev, would have caused a call to suspend the port (usb_port_suspend()), and that would set "suspended_ports" and placed the link in U3 already. > > 2. "suspended_ports" can't differentiate if a device is connected or not after plugging in a USB3 device that has autosuspend enabled. It looks like on device disconnection, the suspended_ports isn't cleared for that port number. It is only cleared during the resume path where a get port status is queried: > > static void xhci_get_usb3_port_status(struct xhci_port *port, u32 *status, > u32 portsc) > { > ... > /* USB3 specific wPortStatus bits */ > if (portsc & PORT_POWER) { > *status |= USB_SS_PORT_STAT_POWER; > /* link state handling */ > if (link_state == XDEV_U0) > bus_state->suspended_ports &= ~(1 << portnum); > } > > IMO, this seems kind of weird, because the PLS shows that the port is in the RxDetect state, so it technically isn't suspended. If you think we should clear suspended_ports on disconnect, then I think we can also change the logic to rely on it for avoiding the unnecessary delay in xhci_resume(). I think you found a bug. We should clear suspended_ports bit if link state in portsc is anything other than U3, Resume or Recovery. Not doing so might cause USB_PORT_STAT_C_SUSPEND bit to be set incorrectly in a USB2 get port status request. So we want something like: if (suspended_ports bit is set) { if (U3 || Resume || Recovery) { don't touch anything } else { clear suspended_port bit if ((U2 || U0) && USB2) set bus_state->port_c_suspend bit } I'll look into it -Mathias
Hi Mathias, On 9/13/2023 7:21 AM, Mathias Nyman wrote: > Hi > > On 13.9.2023 0.51, Wesley Cheng wrote: >> Hi Mathias, >> >>>> This is one way, but we can probably avoid re-reading all the usb3 >>>> portsc registers >>>> by checking if any bit is set in either: >>>> >>>> // bitfield, set if xhci usb3 port neatly set to U3 with a hub >>>> request >>>> xhci->usb3_rhub.bus_state.suspended_ports >>>> >>>> // bitfield, set if xhci usb3 port is forced to U3 during xhci suspend. >>>> xhci->usb3_rhub.bus_state.bus_suspended >>>> >>>> But haven't checked this works in all corner cases. >>>> >>> Thanks for the suggestion. I think I also looked at seeing if we >>> could use the suspended_ports param, and it was missing one of the >>> use cases we had. I haven't thought on combining it with the >>> bus_suspend param also to see if it could work. Let me give it a >>> try, and I'll get back to you. >>> >> >> So in one of our normal use cases, which is to use an USB OTG adapter >> with our devices, we can have this connected with no device. In this >> situation, the XHCI HCD and root hub are enumerated, and is in a state >> where nothing is connected to the port. I added a print to the >> xhci_resume() path to check the status of "suspended_ports" and >> "bus_suspended" and they seem to reflect the same status as when there >> is something connected (to a device that supports autosuspend). >> Here's some pointers I've found on why these parameters may not work: >> >> 1. bus_suspended is only set (for the bus) if we reach the >> bus_suspend() callback from USB HCD if the link is still in U0. If >> USB autosuspend is enabled, then the suspending of the root hub udev, >> would have caused a call to suspend the port (usb_port_suspend()), and >> that would set "suspended_ports" and placed the link in U3 already. >> >> 2. "suspended_ports" can't differentiate if a device is connected or >> not after plugging in a USB3 device that has autosuspend enabled. It >> looks like on device disconnection, the suspended_ports isn't cleared >> for that port number. It is only cleared during the resume path where >> a get port status is queried: >> >> static void xhci_get_usb3_port_status(struct xhci_port *port, u32 >> *status, >> u32 portsc) >> { >> ... >> /* USB3 specific wPortStatus bits */ >> if (portsc & PORT_POWER) { >> *status |= USB_SS_PORT_STAT_POWER; >> /* link state handling */ >> if (link_state == XDEV_U0) >> bus_state->suspended_ports &= ~(1 << portnum); >> } >> >> IMO, this seems kind of weird, because the PLS shows that the port is >> in the RxDetect state, so it technically isn't suspended. If you >> think we should clear suspended_ports on disconnect, then I think we >> can also change the logic to rely on it for avoiding the unnecessary >> delay in xhci_resume(). > > I think you found a bug. > > We should clear suspended_ports bit if link state in portsc is anything > other than U3, Resume or Recovery. > > Not doing so might cause USB_PORT_STAT_C_SUSPEND bit to be set > incorrectly in a USB2 get port status request. > > So we want something like: > if (suspended_ports bit is set) { > if (U3 || Resume || Recovery) { > don't touch anything > } else { > clear suspended_port bit > if ((U2 || U0) && USB2) > set bus_state->port_c_suspend bit > } > > I'll look into it > Thanks, Mathias. Will take some time to take a look as well since I have a reliable set up that observes this issue. If you have any test code you might want to try, let me know! Thanks Wesley Cheng
diff --git a/drivers/usb/host/xhci.c b/drivers/usb/host/xhci.c index e1b1b64a0723..640db6a4e686 100644 --- a/drivers/usb/host/xhci.c +++ b/drivers/usb/host/xhci.c @@ -805,6 +805,24 @@ static void xhci_disable_hub_port_wake(struct xhci_hcd *xhci, spin_unlock_irqrestore(&xhci->lock, flags); } +static bool xhci_usb3_dev_connected(struct xhci_hcd *xhci) +{ + struct xhci_port **ports; + int port_index; + u32 portsc; + + port_index = xhci->usb3_rhub.num_ports; + ports = xhci->usb3_rhub.ports; + + while (port_index--) { + portsc = readl(ports[port_index]->addr); + if (portsc & (portsc & PORT_CONNECT)) + return true; + } + + return false; +} + static bool xhci_pending_portevent(struct xhci_hcd *xhci) { struct xhci_port **ports; @@ -968,6 +986,7 @@ int xhci_resume(struct xhci_hcd *xhci, pm_message_t msg) int retval = 0; bool comp_timer_running = false; bool pending_portevent = false; + bool usb3_connected = false; bool reinit_xhc = false; if (!hcd->state) @@ -1116,9 +1135,14 @@ int xhci_resume(struct xhci_hcd *xhci, pm_message_t msg) * Resume roothubs only if there are pending events. * USB 3 devices resend U3 LFPS wake after a 100ms delay if * the first wake signalling failed, give it that chance. + * Avoid this check if there are no devices connected to + * the SS root hub (i.e. HS device connected or no device + * connected) */ pending_portevent = xhci_pending_portevent(xhci); - if (!pending_portevent && msg.event == PM_EVENT_AUTO_RESUME) { + usb3_connected = xhci_usb3_dev_connected(xhci); + if (!pending_portevent && usb3_connected && + msg.event == PM_EVENT_AUTO_RESUME) { msleep(120); pending_portevent = xhci_pending_portevent(xhci); }
There is a 120ms delay implemented for allowing the XHCI host controller to detect a U3 wakeup pulse. The intention is to wait for the device to retry the wakeup event if the USB3 PORTSC doesn't reflect the RESUME link status by the time it is checked. As per the USB3 specification: tU3WakeupRetryDelay ("Table 7-12. LTSSM State Transition Timeouts") This would allow the XHCI resume sequence to determine if the root hub needs to be also resumed. However, in case there is no device connected, or if there is only a HSUSB device connected, this delay would still affect the overall resume timing. Since this delay is solely for detecting U3 wake events (USB3 specific) then ignore this delay for the disconnected case and the HSUSB connected only case. Signed-off-by: Wesley Cheng <quic_wcheng@quicinc.com> --- drivers/usb/host/xhci.c | 26 +++++++++++++++++++++++++- 1 file changed, 25 insertions(+), 1 deletion(-)