From: RD Babiera rdbabiera@google.com
commit eddebe39602efe631b83ff8d03f26eba12cfd760 upstream.
While determining the initial pin assignment to be sent in the configure message, using the DP_PIN_ASSIGN_DP_ONLY_MASK mask causes the DFP_U to send both Pin Assignment C and E when both are supported by the DFP_U and UFP_U. The spec (Table 5-7 DFP_U Pin Assignment Selection Mandates, VESA DisplayPort Alt Mode Standard v2.0) indicates that the DFP_U never selects Pin Assignment E when Pin Assignment C is offered.
Update the DP_PIN_ASSIGN_DP_ONLY_MASK conditional to intially select only Pin Assignment C if it is available.
Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode") Cc: stable@vger.kernel.org Signed-off-by: RD Babiera rdbabiera@google.com Reviewed-by: Heikki Krogerus heikki.krogerus@linux.intel.com Link: https://lore.kernel.org/r/20230329215159.2046932-1-rdbabiera@google.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/usb/typec/altmodes/displayport.c | 6 +++++- 1 file changed, 5 insertions(+), 1 deletion(-)
--- a/drivers/usb/typec/altmodes/displayport.c +++ b/drivers/usb/typec/altmodes/displayport.c @@ -100,8 +100,12 @@ static int dp_altmode_configure(struct d if (dp->data.status & DP_STATUS_PREFER_MULTI_FUNC && pin_assign & DP_PIN_ASSIGN_MULTI_FUNC_MASK) pin_assign &= DP_PIN_ASSIGN_MULTI_FUNC_MASK; - else if (pin_assign & DP_PIN_ASSIGN_DP_ONLY_MASK) + else if (pin_assign & DP_PIN_ASSIGN_DP_ONLY_MASK) { pin_assign &= DP_PIN_ASSIGN_DP_ONLY_MASK; + /* Default to pin assign C if available */ + if (pin_assign & BIT(DP_PIN_ASSIGN_C)) + pin_assign = BIT(DP_PIN_ASSIGN_C); + }
if (!pin_assign) return -EINVAL;