From df8592973cca9095c385b1f81dd6c0acee076fe0 Mon Sep 17 00:00:00 2001 From: RD Babiera Date: Tue, 10 Mar 2026 20:41:05 +0000 Subject: [PATCH] usb: typec: altmode/displayport: set displayport signaling rate in configure message BugLink: https://bugs.launchpad.net/bugs/2141225 dp_altmode_configure sets the signaling rate to the current configuration's rate and then shifts the value to the Select Configuration bitfield. On the initial configuration, dp->data.conf is 0 to begin with, so the signaling rate field is never set, which leads to some DisplayPort Alt Mode partners sending NAK to the Configure message. Set the signaling rate to the capabilities supported by both the port and the port partner. If the cable supports DisplayPort Alt Mode, then include its capabilities as well. Fixes: a17fae8fc38e ("usb: typec: Add Displayport Alternate Mode 2.1 Support") Cc: stable Signed-off-by: RD Babiera Acked-by: Heikki Krogerus Link: https://patch.msgid.link/20260310204106.3939862-2-rdbabiera@google.com Signed-off-by: Greg Kroah-Hartman (cherry picked from commit e8557acfa079a54b59a21f447c82a31aec7717df) Signed-off-by: Chia-Lin Kao (AceLan) --- drivers/usb/typec/altmodes/displayport.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) diff --git a/drivers/usb/typec/altmodes/displayport.c b/drivers/usb/typec/altmodes/displayport.c index 6462705604510..3edc9dc86b25b 100644 --- a/drivers/usb/typec/altmodes/displayport.c +++ b/drivers/usb/typec/altmodes/displayport.c @@ -100,9 +100,14 @@ static int dp_altmode_configure(struct dp_altmode *dp, u8 con) { u8 pin_assign = 0; u32 conf; + u32 signal; /* DP Signalling */ - conf = (dp->data.conf & DP_CONF_SIGNALLING_MASK) >> DP_CONF_SIGNALLING_SHIFT; + signal = DP_CAP_DP_SIGNALLING(dp->port->vdo) & DP_CAP_DP_SIGNALLING(dp->alt->vdo); + if (dp->plug_prime) + signal &= DP_CAP_DP_SIGNALLING(dp->plug_prime->vdo); + + conf = signal << DP_CONF_SIGNALLING_SHIFT; switch (con) { case DP_STATUS_CON_DISABLED: -- 2.53.0