From: Felipe Balbi <balbi@kernel.org>
To: Bin Liu <b-liu@ti.com>
Cc: Roger Quadros <rogerq@ti.com>, linux-usb@vger.kernel.org
Subject: Re: [PATCH] usb: dwc3: turn off VBUS when leaving host mode
Date: Tue, 10 Dec 2019 13:50:58 +0200 [thread overview]
Message-ID: <875ziol7q5.fsf@gmail.com> (raw)
In-Reply-To: <20191209171522.GA26131@uda0271908>
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Hi,
Bin Liu <b-liu@ti.com> writes:
>> >>> VBUS should be turned off when leaving the host mode.
>> >>> Set GCTL_PRTCAP to device mode in teardown to de-assert DRVVBUS pin to
>> >>> turn off VBUS power.
>> >>>
>> >>> Fixes: 5f94adfeed97 ("usb: dwc3: core: refactor mode initialization to its own function")
>> >>> Signed-off-by: Bin Liu <b-liu@ti.com>
>> >>> ---
>> >>> drivers/usb/dwc3/core.c | 1 +
>> >>> 1 file changed, 1 insertion(+)
>> >>>
>> >>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>> >>> index 97d6ae3c4df2..76ac9cd54e64 100644
>> >>> --- a/drivers/usb/dwc3/core.c
>> >>> +++ b/drivers/usb/dwc3/core.c
>> >>> @@ -1201,6 +1201,7 @@ static void dwc3_core_exit_mode(struct dwc3 *dwc)
>> >>> break;
>> >>> case USB_DR_MODE_HOST:
>> >>> dwc3_host_exit(dwc);
>> >>> + dwc3_set_prtcap(dwc, DWC3_GCTL_PRTCAP_DEVICE);
>> >>
>> >> seems like this should be done as part of dwc3_host_exit()
>> >>
>> >
>> > That wouldn't work well with OTG case as dwc3_host_exit(dwc) is
>> > called when switching roles and we don't want PRTCAP
>> > to change from DWC3_GCTL_PRTCAP_OTG.
>>
>> if (port != OTG)
>> set_prtcap(DEVICE)
>
> During init, the PRTCAP is set in dwc3_core_init_mode() besides
> dwc3_{host,gadget,drd}_init(). So for tearing down setting it in
> dwc3_core_exit_mode() would make the code logic symmetric and easy to
> understand.
Fair enough, makes sense.
> Also it turns out that setting PRTCAP is required for OTG mode too to
But, then, how do we go back to OTG?
> de-assert DRVVBUS. If left GCTL[PRTCAP] to OTG, grounding the ID pin
> would make the controller to assert DRVVBUS without any software
> involved. So the fix should be the following. Please let me know you
> comments.
But that's expected, no? If port is OTG, then it must obey ID pin rules
specified by OTG. IIRC, dwc3 is OTG 2.x compliant, at least the version
TI uses.
--
balbi
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next prev parent reply other threads:[~2019-12-10 11:50 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-13 14:15 [PATCH] usb: dwc3: turn off VBUS when leaving host mode Bin Liu
2019-11-14 8:48 ` Roger Quadros
2019-11-14 14:16 ` Bin Liu
2019-11-18 7:07 ` Felipe Balbi
2019-11-18 9:51 ` Roger Quadros
2019-12-02 7:41 ` Felipe Balbi
2019-12-09 17:15 ` Bin Liu
2019-12-10 11:50 ` Felipe Balbi [this message]
2019-12-10 13:48 ` Bin Liu
2019-12-11 14:41 ` Felipe Balbi
2019-12-11 16:10 ` [PATCH v2] " Bin Liu
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