linux-kernel - Re: [RESEND v2] usb:typec:tcpm:support double Rp to Vbus cable as sink

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Message-ID: <82429728-7158-ed85-975e-55739de217cb@roeck-us.net>
Date:   Thu, 21 Sep 2023 13:39:46 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Michael Wu <michael@...winnertech.com>,
        heikki.krogerus@...ux.intel.com, gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND v2] usb:typec:tcpm:support double Rp to Vbus cable as
 sink

On 9/19/23 23:30, 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>

Reviewed-by: Guenter Roeck <linux@...ck-us.net>

> ---
> v1 -> v2: Simplify expression and add a comment to the code.
> 
>   drivers/usb/typec/tcpm/tcpm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> Signed-off-by: Michael Wu <michael@...winnertech.com>
> ---
>   drivers/usb/typec/tcpm/tcpm.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
> 
> diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
> index d962f67c95ae6..6e843c511b856 100644
> --- a/drivers/usb/typec/tcpm/tcpm.c
> +++ b/drivers/usb/typec/tcpm/tcpm.c
> @@ -517,9 +517,9 @@ static const char * const pd_rev[] = {
>   	((cc) == TYPEC_CC_RP_DEF || (cc) == TYPEC_CC_RP_1_5 || \
>   	 (cc) == TYPEC_CC_RP_3_0)
>   
> +/* As long as cc is pulled up, we can consider it as sink. */
>   #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)->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)