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usb: typec: altmode/displayport: set displayport signaling rate in configure message

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 <stable@kernel.org>
Signed-off-by: RD Babiera <rdbabiera@google.com>
Acked-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://patch.msgid.link/20260310204106.3939862-2-rdbabiera@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

authored by

RD Babiera and committed by
Greg Kroah-Hartman e8557acf 17ab4d40

+6 -1
+6 -1
drivers/usb/typec/altmodes/displayport.c
··· 100 100 { 101 101 u8 pin_assign = 0; 102 102 u32 conf; 103 + u32 signal; 103 104 104 105 /* DP Signalling */ 105 - conf = (dp->data.conf & DP_CONF_SIGNALLING_MASK) >> DP_CONF_SIGNALLING_SHIFT; 106 + signal = DP_CAP_DP_SIGNALLING(dp->port->vdo) & DP_CAP_DP_SIGNALLING(dp->alt->vdo); 107 + if (dp->plug_prime) 108 + signal &= DP_CAP_DP_SIGNALLING(dp->plug_prime->vdo); 109 + 110 + conf = signal << DP_CONF_SIGNALLING_SHIFT; 106 111 107 112 switch (con) { 108 113 case DP_STATUS_CON_DISABLED: