Messages in this thread | | | Date | Mon, 18 Sep 2023 07:22:41 -0700 | From | Guenter Roeck <> | Subject | Re: [PATCH] usb:typec:tcpm:support double Rp to Vbus cable as sink |
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On 9/18/23 03:31, Heikki Krogerus wrote: > 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@allwinnertech.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. >
Look at the conditions. Reordered, we end up with (tcpm_cc_is_sink((port)->cc1) && !tcpm_cc_is_sink((port)->cc2)) || (tcpm_cc_is_sink((port)->cc1) && tcpm_cc_is_sink((port)->cc2)) which simplifies to tcpm_cc_is_sink((port)->cc1) making the complete expression tcpm_cc_is_sink((port)->cc1) || (tcpm_cc_is_sink((port)->cc2) && !tcpm_cc_is_sink((port)->cc1)) which simplifies further to tcpm_cc_is_sink((port)->cc1) || tcpm_cc_is_sink((port)->cc2)
The simplified expression doesn't conflict with other detections, so I am ok with it. It might be worthwhile adding a comment to the code, though, explaining the reason.
Guenter
> thanks, >
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