linux-kernel - Re: [PATCH 1/2] usb typec: tcpci: mt6360: Add vsafe0v support and external vbus supply control

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Date:   Tue, 19 Jan 2021 16:21:08 +0800
From:   ChiYuan Huang <u0084500@...il.com>
To:     Chunfeng Yun <chunfeng.yun@...iatek.com>
Cc:     Guenter Roeck <linux@...ck-us.net>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        matthias.bgg@...il.com, Rob Herring <robh+dt@...nel.org>,
        Greg KH <gregkh@...uxfoundation.org>,
        Linux USB List <linux-usb@...r.kernel.org>,
        linux-arm-kernel@...ts.infradead.org,
        linux-mediatek@...ts.infradead.org,
        lkml <linux-kernel@...r.kernel.org>,
        cy_huang <cy_huang@...htek.com>, gene_chen@...htek.com,
        "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" 
        <devicetree@...r.kernel.org>
Subject: Re: [PATCH 1/2] usb typec: tcpci: mt6360: Add vsafe0v support and
 external vbus supply control

Chunfeng Yun <chunfeng.yun@...iatek.com> 於 2021年1月19日 週二 下午3:33寫道：
>
> On Sun, 2021-01-17 at 09:43 -0800, Guenter Roeck wrote:
> > On 1/15/21 6:13 AM, cy_huang wrote:
> > > From: ChiYuan Huang <cy_huang@...htek.com>
> > >
> > > MT6360 not support for TCPC command to control source and sink.
> >
> > does not
> >
> > > Uses external 5V vbus regulator as the vbus source control.
> > >
> > Use
> >
> > > Also adds the capability to report vsafe0v.
> > >
> > add
> >
> > So far this driver works without regulator. Unless I am missing something,
> > this patch makes regulator support mandatory, meaning existing code will fail.
> If don't provide vbus-supply in DTS, regulator framework will provide a
> dummy regulator, so the code will not fail.
 In the last reply, I will change from regulator_get to
regulator_get_exclusive, it will return -ENODEV.
The IS_ERR can catch this situation, no dummy regulator will be returned.

And assume no vbus 5v for source & snk attached, It will cause typec
state machine repeated from
drp -> src_attach_wait -> src_attached -> PD_T_PS_SOURCE_on timeout.
It will be stuck in the loop until snk detached.

> > I am not sure if that is appropriate/acceptable. Can we be sure that this will
> > work for existing users of this driver ?
>
> >
> > Thanks,
> > Guenter
> >
> > > Signed-off-by: ChiYuan Huang <cy_huang@...htek.com>
> > > ---
> > >  drivers/usb/typec/tcpm/tcpci_mt6360.c | 29 +++++++++++++++++++++++++++++
> > >  1 file changed, 29 insertions(+)
> > >
> > > diff --git a/drivers/usb/typec/tcpm/tcpci_mt6360.c b/drivers/usb/typec/tcpm/tcpci_mt6360.c
> > > index f1bd9e0..0edf4b6 100644
> > > --- a/drivers/usb/typec/tcpm/tcpci_mt6360.c
> > > +++ b/drivers/usb/typec/tcpm/tcpci_mt6360.c
> > > @@ -11,6 +11,7 @@
> > >  #include <linux/of.h>
> > >  #include <linux/platform_device.h>
> > >  #include <linux/regmap.h>
> > > +#include <linux/regulator/consumer.h>
> > >  #include <linux/usb/tcpm.h>
> > >
> > >  #include "tcpci.h"
> > > @@ -36,6 +37,7 @@ struct mt6360_tcpc_info {
> > >     struct tcpci_data tdata;
> > >     struct tcpci *tcpci;
> > >     struct device *dev;
> > > +   struct regulator *vbus;
> > >     int irq;
> > >  };
> > >
> > > @@ -51,6 +53,27 @@ static inline int mt6360_tcpc_write16(struct regmap *regmap,
> > >     return regmap_raw_write(regmap, reg, &val, sizeof(u16));
> > >  }
> > >
> > > +static int mt6360_tcpc_set_vbus(struct tcpci *tcpci, struct tcpci_data *data, bool src, bool snk)
> > > +{
> > > +   struct mt6360_tcpc_info *mti = container_of(data, struct mt6360_tcpc_info, tdata);
> > > +   int ret;
> > > +
> > > +   /* To correctly handle the already enabled vbus and disable its supply first */
> > > +   if (regulator_is_enabled(mti->vbus)) {
> > > +           ret = regulator_disable(mti->vbus);
> > > +           if (ret)
> > > +                   return ret;
> > > +   }
> >
> > Is it really a good idea to disable vbus if it happens to be already enabled
> > and there is (another ?) request to enable it ?
> >
> > > +
> > > +   if (src) {
> > > +           ret = regulator_enable(mti->vbus);
> > > +           if (ret)
> > > +                   return ret;
> > > +   }
> > > +
> > > +   return 0;
> > > +}
> > > +
> > >  static int mt6360_tcpc_init(struct tcpci *tcpci, struct tcpci_data *tdata)
> > >  {
> > >     struct regmap *regmap = tdata->regmap;
> > > @@ -138,7 +161,13 @@ static int mt6360_tcpc_probe(struct platform_device *pdev)
> > >     if (mti->irq < 0)
> > >             return mti->irq;
> > >
> > > +   mti->vbus = devm_regulator_get(&pdev->dev, "vbus");
> > > +   if (IS_ERR(mti->vbus))
> > > +           return PTR_ERR(mti->vbus);
> > > +
> > >     mti->tdata.init = mt6360_tcpc_init;
> > > +   mti->tdata.set_vbus = mt6360_tcpc_set_vbus;
> > > +   mti->tdata.vbus_vsafe0v = 1;
> > >     mti->tcpci = tcpci_register_port(&pdev->dev, &mti->tdata);
> > >     if (IS_ERR(mti->tcpci)) {
> > >             dev_err(&pdev->dev, "Failed to register tcpci port\n");
> > >
> >
>