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: <20170224005703.GA8340@b29397-desktop>
Date:   Fri, 24 Feb 2017 08:57:03 +0800
From:   Peter Chen <hzpeterchen@...il.com>
To:     Vivek Gautam <vivek.gautam@...eaurora.org>
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 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.

-- 

Best Regards,
Peter Chen