Message-ID: <6f188a87-f209-b637-27d6-13dba45906d9@rock-chips.com>
Date:   Mon, 20 Mar 2023 14:28:17 +0800
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Subject: Re: [PATCH 4/4] usb: typec: tcpm: fix source caps may lost after soft
 reset
To:     Guenter Roeck <linux@roeck-us.net>
Cc:     heikki.krogerus@linux.intel.com, gregkh@linuxfoundation.org,
        heiko@sntech.de, linux-usb@vger.kernel.org,
        linux-kernel@vger.kernel.org, linux-rockchip@lists.infradead.org,
        huangtao@rock-chips.com, william.wu@rock-chips.com,
        jianwei.zheng@rock-chips.com, yubing.zhang@rock-chips.com,
        wmc@rock-chips.com
References: <20230313025843.17162-1-frank.wang@rock-chips.com>
 <20230313025843.17162-5-frank.wang@rock-chips.com>
 <f5650fa4-db16-b1e4-f5b4-917fbcabb415@roeck-us.net>
 <867179bc-a21f-5479-f27f-2e17fc5a9a01@rock-chips.com>
 <7038030f-1d7a-4c91-a255-bec73847b7c9@roeck-us.net>
Content-Language: en-US
From:   Frank Wang <frank.wang@rock-chips.com>
In-Reply-To: <7038030f-1d7a-4c91-a255-bec73847b7c9@roeck-us.net>
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Precedence: bulk

Hi Guenter,

On 2023/3/20 11:35, Guenter Roeck wrote:
> On Mon, Mar 20, 2023 at 10:38:35AM +0800, Frank Wang wrote:
>> Hi Guenter,
>>
>> On 2023/3/17 20:58, Guenter Roeck wrote:
>>> On 3/12/23 19:58, Frank Wang wrote:
>>>> Invoke set_pd_rx() may flush the RX FIFO of PD controller, so do
>>>> set_pd_rx() before sending Soft Reset in case Source caps may be flushed
>>>> at debounce time between SOFT_RESET_SEND and SNK_WAIT_CAPABILITIES
>>>> state.
>>>>
>>> Isn't that a problem of the fusb302 driver that it flushes its buffers
>>> unconditionally when its set_pd_rx() callback is called ?
>>>
>>> Guenter
>>>
>> The story goes like this,  the fusb302 notified SOFT_RESET completion to
>> TCPM and began to receive the Source Caps automatically,
>> TCPM got completion from fusb302 and changed state to SNK_WAIT_CAPABILITIES
>> and invoked set_pd_rx() callback. However, the
>> fusb302 or TCPM's worker may be not scheduled in time, set_pd_rx() would be
>> performed after the Source Caps packets had received
>> into fusb302's FIFO, even after the GoodCRC (Source Caps) had be replied.
>>
> Yes, but the fusb302 driver clears its fifo in the set_pd_rx() callback.
> I see that as a problem in the fusb302 driver( it could clear its fifo when
> it notifies the TCPM that soft reset is complete, for example), and I am
> hesitant to work around that problem in the tcpm code.
>
> Guenter

Okay, I shall abandon this from the series.

BR.
Frank

>> So make forward set_pd_rx() process before PD_CTRL_SOFT_RESET sent at
>> SOFT_RESET_SEND state can cleanup the context in our side
>> and ensure the right PD commucation. I am not sure whether it is sensible?
>>
>> BR.
>> Frank
>>
>>>> Without this patch, in PD charger stress test, the FUSB302 driver may
>>>> occur the following exceptions in power negotiation stage.
>>>>
>>>> [ ...]
>>>> [ 4.512252] fusb302_irq_intn
>>>> [ 4.512260] AMS SOFT_RESET_AMS finished
>>>> [ 4.512269] state change SOFT_RESET_SEND ->SNK_WAIT_CAPABILITIES
>>>> [rev3 NONE_AMS]
>>>> [ 4.514511] pd := on
>>>> [ 4.514516] pending state change SNK_WAIT_CAPABILITIES
>>>> ->HARD_RESET_SEND @ 310 ms [rev3 NONE_AMS]
>>>> [ 4.515428] IRQ: 0x51, a: 0x00, b: 0x01, status0: 0x93
>>>> [ 4.515431] IRQ: BC_LVL, handler pending
>>>> [ 4.515435] IRQ: PD sent good CRC
>>>> [ 4.516434] PD message header: 0
>>>> [ 4.516437] PD message len: 0
>>>> [ 4.516444] PD RX, header: 0x0 [1]
>>>>
>>>> Signed-off-by: Frank Wang <frank.wang@rock-chips.com>
>>>> ---
>>>>    drivers/usb/typec/tcpm/tcpm.c | 11 +++++++----
>>>>    1 file changed, 7 insertions(+), 4 deletions(-)
>>>>
>>>> diff --git a/drivers/usb/typec/tcpm/tcpm.c
>>>> b/drivers/usb/typec/tcpm/tcpm.c
>>>> index 9e583060e64fc..ba6bf71838eed 100644
>>>> --- a/drivers/usb/typec/tcpm/tcpm.c
>>>> +++ b/drivers/usb/typec/tcpm/tcpm.c
>>>> @@ -4321,10 +4321,12 @@ static void run_state_machine(struct
>>>> tcpm_port *port)
>>>>            tcpm_set_state(port, unattached_state(port), 0);
>>>>            break;
>>>>        case SNK_WAIT_CAPABILITIES:
>>>> -        ret = port->tcpc->set_pd_rx(port->tcpc, true);
>>>> -        if (ret < 0) {
>>>> -            tcpm_set_state(port, SNK_READY, 0);
>>>> -            break;
>>>> +        if (port->prev_state != SOFT_RESET_SEND) {
>>>> +            ret = port->tcpc->set_pd_rx(port->tcpc, true);
>>>> +            if (ret < 0) {
>>>> +                tcpm_set_state(port, SNK_READY, 0);
>>>> +                break;
>>>> +            }
>>>>            }
>>>>            /*
>>>>             * If VBUS has never been low, and we time out waiting
>>>> @@ -4603,6 +4605,7 @@ static void run_state_machine(struct tcpm_port
>>>> *port)
>>>>        case SOFT_RESET_SEND:
>>>>            port->message_id = 0;
>>>>            port->rx_msgid = -1;
>>>> +        port->tcpc->set_pd_rx(port->tcpc, true);
>>>>            if (tcpm_pd_send_control(port, PD_CTRL_SOFT_RESET))
>>>>                tcpm_set_state_cond(port, hard_reset_state(port), 0);
>>>>            else

-- 
底层平台部 王明成（Frank Wang）
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