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 <[email protected]>
> ---
> 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
Hi Greg,
This patch is a bug fix for the following patch which was introduced in 5.11.
commit f321a02caebdd0c56e167610cda2fa148cd96e8b
Author: Badhri Jagan Sridharan <[email protected]>
Date: Wed Oct 28 23:31:35 2020 -0700
usb: typec: tcpm: Implement enabling Auto Discharge disconnect support
TCPCI spec allows TCPC hardware to autonomously discharge the vbus
capacitance upon disconnect. The expectation is that the TCPM enables
AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
then automously discharges vbus when the vbus falls below a certain
threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.
Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
is also used a flag to move TCPCI based TCPC implementations into
Attached.Snk/Attached.Src state as mentioned in
Figure 4-15. TCPC State Diagram before a Connection of the
USB Type-C Port Controller Interface Specification.
In such TCPC implementations, setting AutoDischargeDisconnect would
prevent TCPC into entering "Connection_Invalid" state as well.
Signed-off-by: Badhri Jagan Sridharan <[email protected]>
Reviewed-by: Heikki Krogerus <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>
Thanks,
Badhri
On Thu, Feb 18, 2021 at 2:10 AM Greg Kroah-Hartman
<[email protected]> wrote:
>
> 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 <[email protected]>
> > ---
> > 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
On Thu, Feb 18, 2021 at 02:38:45AM -0800, Badhri Jagan Sridharan wrote:
> Hi Greg,
>
> This patch is a bug fix for the following patch which was introduced in 5.11.
>
> commit f321a02caebdd0c56e167610cda2fa148cd96e8b
> Author: Badhri Jagan Sridharan <[email protected]>
> Date: Wed Oct 28 23:31:35 2020 -0700
>
> usb: typec: tcpm: Implement enabling Auto Discharge disconnect support
>
> TCPCI spec allows TCPC hardware to autonomously discharge the vbus
> capacitance upon disconnect. The expectation is that the TCPM enables
> AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
> then automously discharges vbus when the vbus falls below a certain
> threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.
>
> Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
> is also used a flag to move TCPCI based TCPC implementations into
> Attached.Snk/Attached.Src state as mentioned in
> Figure 4-15. TCPC State Diagram before a Connection of the
> USB Type-C Port Controller Interface Specification.
> In such TCPC implementations, setting AutoDischargeDisconnect would
> prevent TCPC into entering "Connection_Invalid" state as well.
>
> Signed-off-by: Badhri Jagan Sridharan <[email protected]>
> Reviewed-by: Heikki Krogerus <[email protected]>
> Link: https://lore.kernel.org/r/[email protected]
> Signed-off-by: Greg Kroah-Hartman <[email protected]>
Great, then can you resend the patch and add a proper Fixes: tag, along
with a cc: stable as well?
thanks,
greg k-h
Done. Just sent out the following patch and CCed [email protected] as well.
[PATCH v2] usb: typec: tcpm: Wait for vbus discharge to VSAFE0V before toggling
Thanks,
Badhri
On Thu, Feb 18, 2021 at 2:42 AM Greg Kroah-Hartman
<[email protected]> wrote:
>
> On Thu, Feb 18, 2021 at 02:38:45AM -0800, Badhri Jagan Sridharan wrote:
> > Hi Greg,
> >
> > This patch is a bug fix for the following patch which was introduced in 5.11.
> >
> > commit f321a02caebdd0c56e167610cda2fa148cd96e8b
> > Author: Badhri Jagan Sridharan <[email protected]>
> > Date: Wed Oct 28 23:31:35 2020 -0700
> >
> > usb: typec: tcpm: Implement enabling Auto Discharge disconnect support
> >
> > TCPCI spec allows TCPC hardware to autonomously discharge the vbus
> > capacitance upon disconnect. The expectation is that the TCPM enables
> > AutoDischargeDisconnect while entering SNK/SRC_ATTACHED states. Hardware
> > then automously discharges vbus when the vbus falls below a certain
> > threshold i.e. VBUS_SINK_DISCONNECT_THRESHOLD.
> >
> > Apart from enabling the vbus discharge circuit, AutoDischargeDisconnect
> > is also used a flag to move TCPCI based TCPC implementations into
> > Attached.Snk/Attached.Src state as mentioned in
> > Figure 4-15. TCPC State Diagram before a Connection of the
> > USB Type-C Port Controller Interface Specification.
> > In such TCPC implementations, setting AutoDischargeDisconnect would
> > prevent TCPC into entering "Connection_Invalid" state as well.
> >
> > Signed-off-by: Badhri Jagan Sridharan <[email protected]>
> > Reviewed-by: Heikki Krogerus <[email protected]>
> > Link: https://lore.kernel.org/r/[email protected]
> > Signed-off-by: Greg Kroah-Hartman <[email protected]>
>
> Great, then can you resend the patch and add a proper Fixes: tag, along
> with a cc: stable as well?
>
> thanks,
>
> greg k-h