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

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Date:   Mon, 18 Sep 2023 20:48:44 +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 18-09-23 07:55 pm, Heikki Krogerus wrote:
> On Sat, Sep 16, 2023 at 01:58:30PM +0530, Prashanth K wrote:
>>
>>
>> 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)
> 
> Okay. It would be really interesting to know why is it failing.
> But let's just go with this for now.
> 
> thanks,
> 

Agreed, I'm not really sure why its failing, because its in happening 
the lower layers. Anyways thanks for the comments and review!

Regards,