linux-kernel - Re: [PATCH 4/4] usb: typec: tcpm: fix source caps may lost after soft reset

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Message-ID: <f5650fa4-db16-b1e4-f5b4-917fbcabb415@roeck-us.net>
Date:   Fri, 17 Mar 2023 05:58:06 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Frank Wang <frank.wang@...k-chips.com>,
        heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org,
        heiko@...ech.de
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        linux-rockchip@...ts.infradead.org, huangtao@...k-chips.com,
        william.wu@...k-chips.com, jianwei.zheng@...k-chips.com,
        yubing.zhang@...k-chips.com, wmc@...k-chips.com
Subject: Re: [PATCH 4/4] usb: typec: tcpm: fix source caps may lost after soft
 reset

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

> 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@...k-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