Re: [PATCH v1] usb: typec: tcpm: Wait for vbus discharge to VSAFE0V before toggling

[Greg Kroah-Hartman <gregkh@linuxfoundation.org>]

On Thu, Feb 18, 2021 at 02:02:43AM -0800, Badhri Jagan Sridharan wrote:
> When vbus auto discharge is enabled, TCPM can sometimes be faster than
> the TCPC i.e. TCPM can go ahead and move the port to unattached state
> (involves disabling vbus auto discharge) before TCPC could effectively
> discharge vbus to VSAFE0V. This leaves vbus with residual charge and
> increases the decay time which prevents tsafe0v from being met.
> This change introduces a new state VBUS_DISCHARGE where the TCPM waits
> for a maximum of tSafe0V(max) for vbus to discharge to VSAFE0V before
> transitioning to unattached state and re-enable toggling. If vbus
> discharges to vsafe0v sooner, then, transition to unattached state
> happens right away.
> 
> Also, while in SNK_READY, when auto discharge is enabled, drive
> disconnect based on vbus turning off instead of Rp disappearing on
> CC pins. Rp disappearing on CC pins is almost instanteous compared
> to vbus decay.
> 
> Signed-off-by: Badhri Jagan Sridharan <badhri@google.com>
> ---
>  drivers/usb/typec/tcpm/tcpm.c | 60 +++++++++++++++++++++++++++++++----
>  1 file changed, 53 insertions(+), 7 deletions(-)

As this seems to be a bugfix, what commit does it fix?  Should it go to
stable kernels?  If so, how far back?

And as this is the merge window, I can't do anything with this until
5.12-rc1 is out, so be prepared for the delay...

thanks,

greg k-h