linux-kernel - Re: [PATCH v2 3/4] usb: typec: tcpci: clear the fault status bit

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Date:   Thu, 4 May 2023 16:27:08 +0200
From:   Marco Felsch <m.felsch@...gutronix.de>
To:     Guenter Roeck <linux@...ck-us.net>
Cc:     andreas@...al.se, jun.li@....com,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        Rob Herring <robh+dt@...nel.org>,
        Krzysztof Kozlowski <krzysztof.kozlowski+dt@...aro.org>,
        Bjorn Andersson <andersson@...nel.org>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Shawn Guo <shawnguo@...nel.org>,
        Sascha Hauer <s.hauer@...gutronix.de>,
        Pengutronix Kernel Team <kernel@...gutronix.de>,
        Fabio Estevam <festevam@...il.com>,
        NXP Linux Team <linux-imx@....com>,
        linux-usb@...r.kernel.org, devicetree@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org
Subject: Re: [PATCH v2 3/4] usb: typec: tcpci: clear the fault status bit

On 23-05-04, Guenter Roeck wrote:
> On 5/4/23 06:46, Marco Felsch wrote:
> > According the "USB Type-C Port Controller Interface Specification v2.0"
> > the TCPC sets the fault status register bit-7
> > (AllRegistersResetToDefault) once the registers have been reseted to
> 
> cleared ? set ?

Sry. I don't get this.

> > their default values.
> > 
> > This triggers an alert(-irq) on PTN5110 devices albeit we do mask the
> > fault-irq. Fix this gernally by writing a one to the correspondig
> 
> generically ?

Sure, thanks.

> corresponding

Of course!

> > bit-7.
> > 
> > Signed-off-by: Marco Felsch <m.felsch@...gutronix.de>
> > ---
> >   drivers/usb/typec/tcpm/tcpci.c | 5 +++++
> >   include/linux/usb/tcpci.h      | 1 +
> >   2 files changed, 6 insertions(+)
> > 
> > diff --git a/drivers/usb/typec/tcpm/tcpci.c b/drivers/usb/typec/tcpm/tcpci.c
> > index 8da23240afbe..15632d023e4c 100644
> > --- a/drivers/usb/typec/tcpm/tcpci.c
> > +++ b/drivers/usb/typec/tcpm/tcpci.c
> > @@ -602,6 +602,11 @@ static int tcpci_init(struct tcpc_dev *tcpc)
> >   	if (time_after(jiffies, timeout))
> >   		return -ETIMEDOUT;
> > +	regmap_read(tcpci->regmap, TCPC_FAULT_STATUS, &reg);
> 
> Needs error check.

I will add this.

> Also, I am not sure if this is the correct place for this code. The alert
> status is cleared after vendor initialization. Should the same be done
> here ?

According the spec the bit must be cleared before the TCPC_ALERT is
cleared. Of course the vendor-init can (re-)trigger the bit, therefore
we should move behind the vendor init and right before the TCPC_ALERT
clear.

> Also, why not just write the bit unconditionally, similar
> to TCPC_ALERT ?

Thought about this too.. I will change it in the v3.

Thanks for the feedback,
  Marco

> 
> Thanks,
> Guenter
> 
> > +	if (reg & TCPC_FAULT_STATUS_ALL_REG_RST_TO_DEFAULT)
> > +		tcpci_write16(tcpci, TCPC_FAULT_STATUS,
> > +			      TCPC_FAULT_STATUS_ALL_REG_RST_TO_DEFAULT);
> > +
> >   	/* Handle vendor init */
> >   	if (tcpci->data->init) {
> >   		ret = tcpci->data->init(tcpci, tcpci->data);
> > diff --git a/include/linux/usb/tcpci.h b/include/linux/usb/tcpci.h
> > index 85e95a3251d3..83376473ac76 100644
> > --- a/include/linux/usb/tcpci.h
> > +++ b/include/linux/usb/tcpci.h
> > @@ -103,6 +103,7 @@
> >   #define TCPC_POWER_STATUS_SINKING_VBUS	BIT(0)
> >   #define TCPC_FAULT_STATUS		0x1f
> > +#define TCPC_FAULT_STATUS_ALL_REG_RST_TO_DEFAULT BIT(7)
> >   #define TCPC_ALERT_EXTENDED		0x21
> > 
> 
>