linux-kernel - Re: [PATCH] usb:typec:tcpm:support double Rp to Vbus cable as sink

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Message-ID: <ZQgm/Lb4iZtWrWbs@kuha.fi.intel.com>
Date:   Mon, 18 Sep 2023 13:31:24 +0300
From:   Heikki Krogerus <heikki.krogerus@...ux.intel.com>
To:     Michael Wu <michael@...winnertech.com>
Cc:     linux@...ck-us.net, gregkh@...uxfoundation.org,
        linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] usb:typec:tcpm:support double Rp to Vbus cable as sink

On Thu, Sep 14, 2023 at 08:31:54AM +0800, Michael Wu wrote:
> The USB Type-C Cable and Connector Specification defines the wire
> connections for the USB Type-C to USB 2.0 Standard-A cable assembly
> (Release 2.2, Chapter 3.5.2).
> The Notes says that Pin A5 (CC) of the USB Type-C plug shall be connected
> to Vbus through a resister Rp.
> However, there is a large amount of such double Rp connected to Vbus
> non-standard cables which produced by UGREEN circulating on the market, and
> it can affects the normal operations of the state machine easily,
> especially to CC1 and CC2 be pulled up at the same time.
> In fact, we can regard those cables as sink to avoid abnormal state.
> 
> Message as follow:
> [   58.900212] VBUS on
> [   59.265433] CC1: 0 -> 3, CC2: 0 -> 3 [state TOGGLING, polarity 0, connected]
> [   62.623308] CC1: 3 -> 0, CC2: 3 -> 0 [state TOGGLING, polarity 0, disconnected]
> [   62.625006] VBUS off
> [   62.625012] VBUS VSAFE0V
> 
> Signed-off-by: Michael Wu <michael@...winnertech.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index d962f67c95ae6..beb7143128667 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -519,7 +519,8 @@ static const char * const pd_rev[] = {
>  
>  #define tcpm_port_is_sink(port) \
>  	((tcpm_cc_is_sink((port)->cc1) && !tcpm_cc_is_sink((port)->cc2)) || \
> -	 (tcpm_cc_is_sink((port)->cc2) && !tcpm_cc_is_sink((port)->cc1)))
> +	 (tcpm_cc_is_sink((port)->cc2) && !tcpm_cc_is_sink((port)->cc1)) || \
> +	 (tcpm_cc_is_sink((port)->cc1) && tcpm_cc_is_sink((port)->cc2)))
>  
>  #define tcpm_cc_is_source(cc) ((cc) == TYPEC_CC_RD)
>  #define tcpm_cc_is_audio(cc) ((cc) == TYPEC_CC_RA)

This look OK to me, but I would still like to wait for comments from
Guenter - just in case.

thanks,

-- 
heikki