linux-kernel - Re: usb: typec: ucsi: Clear EVENT_PENDING bit if ucsi_send

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Date:   Sat, 16 Sep 2023 13:58:30 +0530
From:   Prashanth K <quic_prashk@...cinc.com>
To:     Heikki Krogerus <heikki.krogerus@...ux.intel.com>
CC:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        <linux-usb@...r.kernel.org>, <linux-kernel@...r.kernel.org>,
        "# 5 . 16" <stable@...r.kernel.org>
Subject: Re: usb: typec: ucsi: Clear EVENT_PENDING bit if ucsi_send_command
 fails



On 15-09-23 07:27 pm, Heikki Krogerus wrote:
> Hi Prashanth,
> 
> On Fri, Sep 15, 2023 at 07:10:25PM +0530, Prashanth K wrote:
>> On 15-09-23 06:02 pm, Heikki Krogerus wrote:
>>> On Tue, Sep 12, 2023 at 04:37:47PM +0530, Prashanth K wrote:
>>>>
>>>>
>>>> On 11-09-23 06:19 pm, Heikki Krogerus wrote:
>>>>> On Mon, Sep 11, 2023 at 02:34:15PM +0530, Prashanth K wrote:
>>>>>> Currently if ucsi_send_command() fails, then we bail out without
>>>>>> clearing EVENT_PENDING flag. So when the next connector change
>>>>>> event comes, ucsi_connector_change() won't queue the con->work,
>>>>>> because of which none of the new events will be processed.
>>>>>>
>>>>>> Fix this by clearing EVENT_PENDING flag if ucsi_send_command()
>>>>>> fails.
>>>>>>
>>>>>> Cc: <stable@...r.kernel.org> # 5.16
>>>>>> Fixes: 512df95b9432 ("usb: typec: ucsi: Better fix for missing unplug events issue")
>>>>>> Signed-off-by: Prashanth K <quic_prashk@...cinc.com>
>>>>>> ---
>>>>>>     drivers/usb/typec/ucsi/ucsi.c | 1 +
>>>>>>     1 file changed, 1 insertion(+)
>>>>>>
>>>>>> diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
>>>>>> index c6dfe3d..509c67c 100644
>>>>>> --- a/drivers/usb/typec/ucsi/ucsi.c
>>>>>> +++ b/drivers/usb/typec/ucsi/ucsi.c
>>>>>> @@ -884,6 +884,7 @@ static void ucsi_handle_connector_change(struct work_struct *work)
>>>>>>     	if (ret < 0) {
>>>>>>     		dev_err(ucsi->dev, "%s: GET_CONNECTOR_STATUS failed (%d)\n",
>>>>>>     			__func__, ret);
>>>>>> +		clear_bit(EVENT_PENDING, &con->ucsi->flags);
>>>>>>     		goto out_unlock;
>>>>>>     	}
>>>>>
>>>>> I think it would be better to just move that label (out_unlock) above
>>>>> the point where clear_bit() is already called instead of separately
>>>>> calling it like that. That way the Connector Change Event will
>>>>> also get acknowledged.
>>>> Do we really need to ACK in this case since we didn't process the current
>>>> connector change event
>>>
>>> You won't get the next event before the first one was ACK'd, right?
>>>
>>
>> The spec says that we need to ACK if we received AND processed a CCI
>>
>> "4.5.4 Acknowledge Command Completion and/or Change Indication (R)
>> This command is used to acknowledge to the PPM that the OPM received and
>> processed a Command Completion and/or a Connector Change Indication."
>>
>> And here in this case, we have received, but not processed the event.
>> So I'm not really sure what to do here in this case. If we don't send an
>> ACK, then would the PPM think that OPM is not responding and reset it?
>> OR would it resend the previous event again since we didn't ACK?
> 
> Every PPM behaves differently.
> 
> Did you actually see that happening - GET_CONNECTOR_STATUS failed? Can
> you reproduce it?
> 

Yea we actually hit the issue once where GET_CONNECTOR_STATUS failed and 
subsequent events didn't get queued since EVENT_PENDING wasn't cleared. 
Its not easily reproducible (<1%) though.

[4948:kworker/0:3]UCSI: ucsi_qti_glink_write: timed out
[4948:kworker/0:3]ucsi_glink soc:qcom,pmic_glink:qcom,ucsi: 
ucsi_handle_connector_change: GET_CONNECTOR_STATUS failed (-110)

Regards,
Prashanth K