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

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Message-ID: <670c3604-7287-ed7d-8e37-b0458ff28ca8@roeck-us.net>
Date:   Thu, 4 May 2023 08:27:31 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Marco Felsch <m.felsch@...gutronix.de>
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 5/4/23 07:27, Marco Felsch wrote:
> 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.
> 

instead of "reseted" which isn't really a word.

>>> 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
>>>
>>
>>