gk7205v200_otg: settle the USB role before xHCI probes (#147)
The OTG profile could not see USB devices in host mode. On a board with a UVC webcam on the USB tail, `lsusb` showed only the two root hubs, while the same board running a plain lite image enumerated the webcam normally. The controller was in the host role and the host controller was running -- mode file "host", xhci-hcd bound, USBCMD 0x5, PORTSC1 port-power set -- and the port still never reported a connect (PORTSC1 0x00000280, CCS clear). dr_mode = "otg" makes dwc3_core_init() program GCTL.PRTCAPDIR = OTG(3), and dwc3_core_init_mode() registers xhci-hcd on top of that. This 4.9 dwc3 has no working OTG role-detection block, so xHCI probes, resets the controller and brings up its root hubs while the core is in a role it cannot drive. The port is then dead for the life of that probe. S72usbmode's `usb-mode host` did not repair it and could not: writing the debugfs mode file reaches dwc3_set_mode(), which flips GCTL.PRTCAPDIR and nothing else, leaving the already-probed xHCI with the port state machine it built in OTG. It also skipped the bind, because xhci-hcd was already bound. Fix it where the ordering is: patch dwc3_core_init() to program PRTCAPDIR = HOST for the OTG case, so xHCI probes into a role the core can drive. dwc3_gadget_init() only registers a UDC and does not care, and `usb-mode device` re-aims the controller itself when it takes the port. usb-mode's host path also learns to re-probe an xHCI that was bound in some other role, which is what makes a newer rootfs recover on an older kernel.
This commit is contained in:
OpenIPC AI team
@@ -2,12 +2,13 @@
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#
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# Force a concrete USB role at boot.
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#
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# This is NOT optional on this board. The device tree sets dr_mode = "otg" so
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# that dwc3 registers both an xHCI host and a UDC, which is what makes runtime
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# role switching possible. But dwc3_core_init() then leaves
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# GCTL.PRTCAPDIR = OTG(3), and this 4.9 dwc3 has no working OTG role-detection
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# block -- nothing ever moves it off OTG on its own. Left alone the controller
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# sits in a role it cannot drive and USB works in neither direction.
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# The device tree sets dr_mode = "otg" so that dwc3 registers both an xHCI host
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# and a UDC, which is what makes runtime role switching possible. The role
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# itself is settled in the kernel: all-patches 0018 programs
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# GCTL.PRTCAPDIR = HOST before the xHCI host is registered, because a host that
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# probes while the core is still in OTG(3) comes up unable to drive the port --
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# it runs, powers the port, and never reports a connect. So the board boots as
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# a host, and this script exists to apply a persisted "device" choice on top.
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#
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# Runs after S70vendor so the vendor modules are up first.
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@@ -99,18 +99,15 @@ to_device() {
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need_debugfs
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if X=$(xhci_device) && [ -e "/sys/bus/platform/drivers/xhci-hcd/$X" ]; then
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# Coming straight from boot the controller is still in its power-on
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# GCTL.PRTCAPDIR = OTG(3) (see the header note: nothing moves it off
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# OTG on its own). xhci-hcd binds and registers both buses on top of
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# that anyway, but it is not actually driving the port -- so unbinding
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# directly from OTG asks xhci_halt() to halt a host that was never
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# really running, and it times out:
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# Unbind only from the host role. Asking xhci_halt() to halt a
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# controller whose GCTL.PRTCAPDIR is not HOST means halting a host
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# that was never really running, and it times out:
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# xhci-hcd.0.auto: Host not halted after 16000 microseconds.
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# xhci-hcd.0.auto: Host controller not halted, aborting reset.
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# Leaving the controller un-halted is precisely the live-DMA-engine
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# state this unbind exists to avoid. Flip to host first so the already
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# bound xHCI is genuinely running, and the unbind then halts cleanly.
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# A switch from host is already in that state, so only boot pays for it.
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# Leaving it un-halted is precisely the live-DMA-engine state this
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# unbind exists to avoid. Since all-patches 0018 the core is already
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# in the host role whenever xHCI is bound, so this flip is a no-op; it
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# stays as the cheap guarantee that the unbind below halts cleanly.
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[ "$(cat "$MODE_FILE")" = host ] || echo host > "$MODE_FILE"
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echo "usb-mode: unbinding host controller $X"
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@@ -141,11 +138,32 @@ to_host() {
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teardown_gadget
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# Remember which role we are leaving: it decides whether an already-bound
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# host stack has to be re-probed. See below.
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was=$(cat "$MODE_FILE")
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echo host > "$MODE_FILE"
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if X=$(xhci_device) && [ ! -e "/sys/bus/platform/drivers/xhci-hcd/$X" ]; then
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echo "usb-mode: rebinding host controller $X"
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echo "$X" > /sys/bus/platform/drivers/xhci-hcd/bind
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if X=$(xhci_device); then
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if [ ! -e "/sys/bus/platform/drivers/xhci-hcd/$X" ]; then
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echo "usb-mode: rebinding host controller $X"
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echo "$X" > /sys/bus/platform/drivers/xhci-hcd/bind
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elif [ "$was" != host ]; then
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# Bound, but bound while the core was in another role: it
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# probed, reset the controller and brought up its root hubs
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# against a port it was not driving, and it will never report a
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# connect -- the port powers up and stays at CCS = 0, so lsusb
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# shows nothing but the root hubs however many devices are
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# plugged in. Writing MODE_FILE only flips GCTL.PRTCAPDIR; it
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# does not re-initialise a live xHCI. Making it probe again is
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# what actually brings the port up.
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#
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# The kernel now settles the role before registering the host
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# (all-patches 0018), so this cannot trigger on a matching
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# kernel. It is here for a rootfs running on an older one.
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echo "usb-mode: re-probing host controller $X (was $was)"
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echo "$X" > /sys/bus/platform/drivers/xhci-hcd/unbind
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echo "$X" > /sys/bus/platform/drivers/xhci-hcd/bind
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fi
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fi
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echo host > "$STATE"
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+6
-4
@@ -18,11 +18,13 @@ same node (eps_directions, eps_map, snps,eps_new_init), which the vendor would
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only have added if device mode was exercised; and CONFIG_USB_DWC3_DUAL_ROLE is
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already enabled, so dwc3's gadget.o/ep0.o are already linked in.
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IMPORTANT: dr_mode = "otg" also makes dwc3_core_init() leave
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IMPORTANT: on its own, dr_mode = "otg" would also make dwc3_core_init() leave
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GCTL.PRTCAPDIR = OTG(3), and this 4.9 dwc3 has no working OTG role-detection
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block. A concrete role must be forced early in userspace -- see
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/etc/init.d/S72usbmode, which writes "host" at boot. Without it the controller
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sits in a role it cannot drive and USB does not work in either direction.
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block -- nothing would ever move it off OTG, and an xHCI host that probes in
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that state comes up unable to drive the port. Patch 0018 settles the role in
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the kernel instead, programming PRTCAPDIR = HOST before the host is
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registered, so the board boots usable as a host; /etc/init.d/S72usbmode then
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only has to apply a persisted "device" choice.
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This patch ships only in the gk7205v200_otg_generic device profile, so other
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gk7205v200 variants keep dr_mode = "host".
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+60
@@ -0,0 +1,60 @@
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From: OpenIPC
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Subject: [PATCH] usb: dwc3: start a dual-role part in the host role, not in OTG
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With dr_mode = "otg", dwc3_core_init() programs GCTL.PRTCAPDIR = OTG(3) and
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dwc3_core_init_mode() then registers the xHCI host on top of it. This 4.9 dwc3
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has no working OTG role-detection block, so nothing ever moves the controller
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off OTG on its own -- xhci-hcd probes, resets the controller and brings up its
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root hubs while the core is in a role it cannot drive.
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The result is a host controller that looks completely healthy and does nothing.
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Measured on gk7205v200 with a UVC webcam wired to the USB tail:
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USBCMD 0x00000005 R/S set, controller running
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PORTSC1 0x00000280 PP set, CCS clear -- no connect, ever
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lsusb only the two root hubs
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The port never reports the connect, so `lsusb` on the OTG image shows nothing
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attached while the same board on a dr_mode = "host" image enumerates the webcam
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normally. This is the bug users hit as "the OTG firmware does not see USB
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devices".
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Forcing the role from userspace afterwards does not repair it. Writing "host"
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to /sys/kernel/debug/<dwc3>/mode reaches dwc3_set_mode(), which flips
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GCTL.PRTCAPDIR and nothing else; the already-probed xHCI keeps the port state
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machine it initialised while the core was in OTG. Confirmed by experiment: the
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write leaves PORTSC1 at 0x00000280, and only unbinding and re-binding xhci-hcd
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-- i.e. making it probe again, with the core now in host role -- brings the
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port up (PORTSC1 0x0C000E63, device enumerated).
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So the role has to be concrete before the host stack is registered. Set
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PRTCAPDIR = HOST for the OTG case: dwc3_core_init() runs before
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dwc3_core_init_mode(), so xHCI probes into a role the core can drive.
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This costs the gadget nothing. dwc3_gadget_init() only registers a UDC, which
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does not care about PRTCAPDIR, and the device role is entered explicitly by
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`usb-mode device` (which flips PRTCAPDIR after unbinding the host). Booting in
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the host role is also what upstream settled on: __dwc3_set_mode() treats
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DWC3_GCTL_PRTCAP_OTG as "pick a role now" rather than as a state to sit in.
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--- a/drivers/usb/dwc3/core.c
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+++ b/drivers/usb/dwc3/core.c
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@@ -755,7 +755,17 @@
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dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_HOST);
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break;
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case USB_DR_MODE_OTG:
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- dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_OTG);
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+ /*
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+ * Deliberately HOST and not OTG: dwc3_core_init_mode() is
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+ * about to register xhci-hcd, and a host that probes while
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+ * the core sits in OTG comes up unable to drive the port --
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+ * it runs, powers the port and never sees a connect. Nothing
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+ * in this tree moves the core off OTG later, and flipping
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+ * PRTCAPDIR afterwards does not re-initialise the host, so
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+ * the role must be settled here. The gadget path re-aims the
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+ * controller itself when it takes the port.
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+ */
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+ dwc3_set_mode(dwc, DWC3_GCTL_PRTCAP_HOST);
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break;
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default:
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dev_warn(dwc->dev, "Unsupported mode %d\n", dwc->dr_mode);
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