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usb: typec: altmodes/displayport: Fix configure initial pin assignment

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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>
This commit is contained in:
RD Babiera 2023-03-29 21:51:59 +00:00 committed by Greg Kroah-Hartman
parent f417d3fea3
commit 38c00a22d6
1 changed files with 5 additions and 1 deletions
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6
drivers/usb/typec/altmodes/displayport.c
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@ -100,8 +100,12 @@ static int dp_altmode_configure(struct dp_altmode *dp, u8 con)
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;