On 2017-11-01 02:38, Peter Chen wrote: > On Tue, Oct 31, 2017 at 06:07:39PM +0100, Stefan Agner wrote: >> Hi Peter, >> >> I am currently trying to come up with a upstreamable solution for USB >> device/host switch for our NXP i.MX 7 CoM (Colibri iMX7). My colleague >> Sanchayan already posted on the mailing list in a earlier attempt for >> our Colibri VFxx modules (NXP Vybrid): >> http://www.spinics.net/lists/linux-usb/msg140810.html >> >> The situation is very similar: The device is not OTG capable, but just >> allows to use a Micro-USB connector as Host when using a OTG cable. VBUS >> is enabled in hardware depending on ID-Pin. We have a single 3.3V input >> to the module "usbc_det". Back then your advice was to wait for the DCD >> framework, however, reading up on the mailing list discussion it seems >> that this did not make it mainline in a form it would be easily usable >> with the Chipidea IP: >> https://patchwork.kernel.org/patch/9172269/ >> >> Downstream we currently use a custom "state machine" which directly >> calls ci_role_stop/start and usb_gadget_vbus_(dis)connect: >> http://git.toradex.com/cgit/linux-toradex.git/commit/drivers/usb/chipidea/core.c?h=toradex_4.1-2.0.x-imx-next&id=1f43d373946ee34ce0cfeb667a9aa48d6995bfea >> >> I tried to use the Chipidea OTG FSM and extcon. The device tree bindings >> state: >> > - extcon: phandles to external connector devices. First phandle should point to >> > external connector, which provide "USB" cable events, the second should point >> > to external connector device, which provide "USB-HOST" cable events. If one >> > of the external connector devices is not required, empty <0> phandle should >> > be specified. >> >> It sounds like any of the two extcon are optional, also in >> drivers/usb/chipidea/core.c a comment notes: "Each one of them is not >> mandatory" >> >> On Colibri iMX7 the usbc_det is also connected to USB_OTG1_VBUS, and it >> leads to a proper B Session Valid in OTGSC registers. >> >> So I tried specifying ID only (since VBUS is switched in hardware and >> can be detected through B Session Valid), but this seems not to be stuck >> in the OTG FSM (with an additional debug print in ci_otg_fsm_event): >> [ 264.327871] ci_otg_fsm_irq >> [ 264.333153] ci_hdrc ci_hdrc.0: ci_otg_fsm_event a_wait_vrise >> [ 264.347984] ci_cable_notifier, event 0 >> [ 264.354329] ci_otg_fsm_irq >> [ 265.360930] ci_hdrc ci_hdrc.0: remove, state 4 >> [ 265.367862] usb usb1: USB disconnect, device number 1 >> [ 265.380912] ci_hdrc ci_hdrc.0: USB bus 1 deregistered >> >> It seems to me that the CI OTG FSM is too complex for what I am trying >> to achieve. Any advice how I should go about it? >> > > Stefan, if you only search for solution for dual-role switch through > ID pin, you do not need OTG FSM. Just keep your vbus and ID value are > correct during every manual operation. Not sure I understand, it should switch automatically... -- Stefan -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
