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

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Date:   Fri, 15 Sep 2023 19:10:25 +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 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?

Regards,
Prashanth K