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Message-ID: <1621835511.26501.14.camel@mhfsdcap03>
Date: Mon, 24 May 2021 13:51:51 +0800
From: Chunfeng Yun <chunfeng.yun@...iatek.com>
To: Thierry Reding <treding@...dia.com>
CC: Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Liam Girdwood <lgirdwood@...il.com>,
Mark Brown <broonie@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>,
Paul Cercueil <paul@...pouillou.net>,
Lee Jones <lee.jones@...aro.org>, <linux-usb@...r.kernel.org>,
<linux-kernel@...r.kernel.org>,
<linux-arm-kernel@...ts.infradead.org>,
<linux-mediatek@...ts.infradead.org>
Subject: Re: [PATCH v2 3/3] Revert "usb: common: usb-conn-gpio: Make VBUS
supply optional"
On Fri, 2021-05-21 at 15:20 +0200, Thierry Reding wrote:
> On Wed, May 19, 2021 at 02:39:46PM +0800, Chunfeng Yun wrote:
> > Vbus is already an optional supply, if the vbus-supply is not
> > provided in DTS, will use a dummy regulator,
>
> That statement is not entirely correct. The dummy regulator is
> substituted only if the supply is in fact not optional. The idea behind
> that is to allow DTS files that don't specify all required regulators to
> get away with it, based on the assumption that the supply is one of
> those always-on supplies that are often not described in DTS.
Yes, you are right.
But from the point of result, it indeed can help to handle the absent
regulator.
>
> > the warning log is as below:
> > "supply vbus not found, using dummy regulator"
>
> And the reason why we get that warning is to point out that the DTS has
> a bug and that it should be fixed (by adding a proper regulator to take
> the place of the dummy).
>
> > This reverts commit 4ddf1ac79e5f082451cd549283d2eb7559ab6ca9.
>
> But if you read the description of that commit, the purpose of that
> patch was in fact to make the supply completely optional in the case
> where we already have the VBUS supply specified for the USB port that
> the connector is parented to.
Could you please give an example you mentioned?
It seems prefer to provide vbus supply in connector instead of port
according to dt-binding
Thanks
>
> So in that case the DTS doesn't have the bug because the VBUS supply is
> already specified for the USB port and therefore it doesn't have to be
> specified in the USB connector again. In fact, specifying it twice can
> lead to a situation where the USB port may not be able to switch the
> VBUS supply on or off because the setting might conflict with that of
> the USB connector.
>
> So unless there's a real reason why this is needed, I don't think this
> should be applied.
>
> Thierry
>
> > Cc: Thierry Reding <treding@...dia.com>
> > Signed-off-by: Chunfeng Yun <chunfeng.yun@...iatek.com>
> > ---
> > v2: remove unused variable "need_vbus"
> > ---
> > drivers/usb/common/usb-conn-gpio.c | 30 ++++++------------------------
> > 1 file changed, 6 insertions(+), 24 deletions(-)
> >
> > diff --git a/drivers/usb/common/usb-conn-gpio.c b/drivers/usb/common/usb-conn-gpio.c
> > index dfbbc4f51ed6..65d89140cd19 100644
> > --- a/drivers/usb/common/usb-conn-gpio.c
> > +++ b/drivers/usb/common/usb-conn-gpio.c
> > @@ -91,14 +91,14 @@ static void usb_conn_detect_cable(struct work_struct *work)
> > return;
> > }
> >
> > - if (info->last_role == USB_ROLE_HOST && info->vbus)
> > + if (info->last_role == USB_ROLE_HOST)
> > regulator_disable(info->vbus);
> >
> > ret = usb_role_switch_set_role(info->role_sw, role);
> > if (ret)
> > dev_err(info->dev, "failed to set role: %d\n", ret);
> >
> > - if (role == USB_ROLE_HOST && info->vbus) {
> > + if (role == USB_ROLE_HOST) {
> > ret = regulator_enable(info->vbus);
> > if (ret)
> > dev_err(info->dev, "enable vbus regulator failed\n");
> > @@ -106,9 +106,8 @@ static void usb_conn_detect_cable(struct work_struct *work)
> >
> > info->last_role = role;
> >
> > - if (info->vbus)
> > - dev_dbg(info->dev, "vbus regulator is %s\n",
> > - regulator_is_enabled(info->vbus) ? "enabled" : "disabled");
> > + dev_dbg(info->dev, "vbus regulator is %s\n",
> > + regulator_is_enabled(info->vbus) ? "enabled" : "disabled");
> >
> > power_supply_changed(info->charger);
> > }
> > @@ -175,7 +174,6 @@ static int usb_conn_probe(struct platform_device *pdev)
> > {
> > struct device *dev = &pdev->dev;
> > struct usb_conn_info *info;
> > - bool need_vbus = true;
> > int ret = 0;
> >
> > info = devm_kzalloc(dev, sizeof(*info), GFP_KERNEL);
> > @@ -205,23 +203,7 @@ static int usb_conn_probe(struct platform_device *pdev)
> >
> > INIT_DELAYED_WORK(&info->dw_det, usb_conn_detect_cable);
> >
> > - /*
> > - * If the USB connector is a child of a USB port and that port already provides the VBUS
> > - * supply, there's no need for the USB connector to provide it again.
> > - */
> > - if (dev->parent && dev->parent->of_node) {
> > - if (of_find_property(dev->parent->of_node, "vbus-supply", NULL))
> > - need_vbus = false;
> > - }
> > -
> > - if (!need_vbus) {
> > - info->vbus = devm_regulator_get_optional(dev, "vbus");
> > - if (PTR_ERR(info->vbus) == -ENODEV)
> > - info->vbus = NULL;
> > - } else {
> > - info->vbus = devm_regulator_get(dev, "vbus");
> > - }
> > -
> > + info->vbus = devm_regulator_get(dev, "vbus");
> > if (IS_ERR(info->vbus)) {
> > ret = PTR_ERR(info->vbus);
> > return dev_err_probe(dev, ret, "failed to get vbus :%d\n", ret);
> > @@ -288,7 +270,7 @@ static int usb_conn_remove(struct platform_device *pdev)
> >
> > cancel_delayed_work_sync(&info->dw_det);
> >
> > - if (info->last_role == USB_ROLE_HOST && info->vbus)
> > + if (info->last_role == USB_ROLE_HOST)
> > regulator_disable(info->vbus);
> >
> > usb_role_switch_put(info->role_sw);
> > --
> > 2.18.0
> >
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