linux-kernel - Re: [PATCH v2 4/4] usb: dwc3: Workaround for super-speed host on dra7 in dual-role mode

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Message-ID: <88b3eb2d-feb7-fd34-2f83-12bee6970779@codeaurora.org>
Date:   Fri, 24 Feb 2017 08:38:34 +0530
From:   Vivek Gautam <vivek.gautam@...eaurora.org>
To:     Peter Chen <hzpeterchen@...il.com>
Cc:     Roger Quadros <rogerq@...com>, balbi@...nel.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 4/4] usb: dwc3: Workaround for super-speed host on dra7
 in dual-role mode



On 02/24/2017 06:27 AM, Peter Chen wrote:
> On Thu, Feb 23, 2017 at 02:04:50PM +0530, Vivek Gautam wrote:
>>
>> On 02/16/2017 06:36 PM, Roger Quadros wrote:
>>> dra7 OTG core limits the host controller to USB2.0 (high-speed) mode
>>> when we're operating in dual-role.
>>>
>>> We work around that by bypassing the OTG core and reading the
>>> extcon framework directly for ID/VBUS events.
>>>
>>> Signed-off-by: Roger Quadros <rogerq@...com>
>>> ---
>>>   Documentation/devicetree/bindings/usb/dwc3.txt |   2 +
>>>   drivers/usb/dwc3/core.c                        | 169 ++++++++++++++++++++++++-
>>>   drivers/usb/dwc3/core.h                        |   5 +
>>>   3 files changed, 170 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/Documentation/devicetree/bindings/usb/dwc3.txt b/Documentation/devicetree/bindings/usb/dwc3.txt
>>> index e3e6983..9955c0d 100644
>>> --- a/Documentation/devicetree/bindings/usb/dwc3.txt
>>> +++ b/Documentation/devicetree/bindings/usb/dwc3.txt
>>> @@ -53,6 +53,8 @@ Optional properties:
>>>    - snps,quirk-frame-length-adjustment: Value for GFLADJ_30MHZ field of GFLADJ
>>>   	register for post-silicon frame length adjustment when the
>>>   	fladj_30mhz_sdbnd signal is invalid or incorrect.
>>> + - extcon: phandle to the USB connector extcon device. If present, extcon
>>> +	device will be used to get USB cable events instead of OTG controller.
>>>    - <DEPRECATED> tx-fifo-resize: determines if the FIFO *has* to be reallocated.
>>> diff --git a/drivers/usb/dwc3/core.c b/drivers/usb/dwc3/core.c
>>> index 619fa7c..b02d911 100644
>>> --- a/drivers/usb/dwc3/core.c
>>> +++ b/drivers/usb/dwc3/core.c
>> [snip]
>>
>>> @@ -1587,6 +1727,14 @@ static int dwc3_probe(struct platform_device *pdev)
>>>   	dwc3_get_properties(dwc);
>>> +	if (dev->of_node) {
>>> +		if (of_property_read_bool(dev->of_node, "extcon"))
>>> +			dwc->edev = extcon_get_edev_by_phandle(dev, 0);
>> Don't we want separate edev's for vbus and id ?
>> One can have separate pins connected to them and in that case
>> we can't get the events out of one pin only.
>>
> Current extcon-usb-gpio driver supports id and vbus at the same time,
> that means there are two optional gpios under one extcon node.
>

Right, and we would want to leverage that by providing couple
of phandles for vbus and id, and requesting the two in driver.


Regards
Vivek

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