Re: [PATCH] usb: typec: tcpm: always rediscover when swapping DR

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On 8/17/21 2:36 AM, Heikki Krogerus wrote:
On Fri, Aug 13, 2021 at 12:31:31PM +0800, Icenowy Zheng wrote:
Currently, TCPM code omits discover when swapping to gadget, and assume
that no altmodes are available when swapping from gadget. However, we do
send discover when we get attached as gadget -- this leads to modes to be
discovered twice when attached as gadget and then swap to host.

Always re-send discover when swapping DR, regardless of what change is
being made; and because of this, the assumption that no altmodes are
registered with gadget role is broken, and altmodes de-registeration is
always needed now.

Signed-off-by: Icenowy Zheng <icenowy@xxxxxxx>
---
  drivers/usb/typec/tcpm/tcpm.c | 9 ++++-----
  1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index b9bb63d749ec..ab6d0d51ee1c 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -4495,15 +4495,14 @@ static void run_state_machine(struct tcpm_port *port)
  		tcpm_set_state(port, ready_state(port), 0);
  		break;
  	case DR_SWAP_CHANGE_DR:
-		if (port->data_role == TYPEC_HOST) {
-			tcpm_unregister_altmodes(port);
+		tcpm_unregister_altmodes(port);
+		if (port->data_role == TYPEC_HOST)
  			tcpm_set_roles(port, true, port->pwr_role,
  				       TYPEC_DEVICE);
-		} else {
+		else
  			tcpm_set_roles(port, true, port->pwr_role,
  				       TYPEC_HOST);
-			port->send_discover = true;
-		}
+		port->send_discover = true;
  		tcpm_ams_finish(port);
  		tcpm_set_state(port, ready_state(port), 0);
  		break;

Why is it necessary to do discovery with data role swap in general?

thanks,


Additional question: There are two patches pending related to DR_SWAP
and discovery. Are they both needed, or do they both solve the same
problem ?

Thanks,
Guenter



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