linux-kernel - [PATCH 5.15 075/107] usb: typec: altmodes/displayport: correct pin assignment for UFP receptacles

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Message-Id: <20220906132824.980232602@linuxfoundation.org>
Date:   Tue,  6 Sep 2022 15:30:56 +0200
From:   Greg Kroah-Hartman <gregkh@...uxfoundation.org>
To:     linux-kernel@...r.kernel.org
Cc:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        stable@...r.kernel.org, Guillaume Ranquet <granquet@...libre.com>,
        Heikki Krogerus <heikki.krogerus@...ux.intel.com>,
        Pablo Sun <pablo.sun@...iatek.com>,
        Macpaul Lin <macpaul.lin@...iatek.com>
Subject: [PATCH 5.15 075/107] usb: typec: altmodes/displayport: correct pin assignment for UFP receptacles

From: Pablo Sun <pablo.sun@...iatek.com>

commit c1e5c2f0cb8a22ec2e14af92afc7006491bebabb upstream.

Fix incorrect pin assignment values when connecting to a monitor with
Type-C receptacle instead of a plug.

According to specification, an UFP_D receptacle's pin assignment
should came from the UFP_D pin assignments field (bit 23:16), while
an UFP_D plug's assignments are described in the DFP_D pin assignments
(bit 15:8) during Mode Discovery.

For example the LG 27 UL850-W is a monitor with Type-C receptacle.
The monitor responds to MODE DISCOVERY command with following
DisplayPort Capability flag:

        dp->alt->vdo=0x140045

The existing logic only take cares of UPF_D plug case,
and would take the bit 15:8 for this 0x140045 case.

This results in an non-existing pin assignment 0x0 in
dp_altmode_configure.

To fix this problem a new set of macros are introduced
to take plug/receptacle differences into consideration.

Fixes: 0e3bb7d6894d ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: stable@...r.kernel.org
Co-developed-by: Pablo Sun <pablo.sun@...iatek.com>
Co-developed-by: Macpaul Lin <macpaul.lin@...iatek.com>
Reviewed-by: Guillaume Ranquet <granquet@...libre.com>
Reviewed-by: Heikki Krogerus <heikki.krogerus@...ux.intel.com>
Signed-off-by: Pablo Sun <pablo.sun@...iatek.com>
Signed-off-by: Macpaul Lin <macpaul.lin@...iatek.com>
Link: https://lore.kernel.org/r/20220804034803.19486-1-macpaul.lin@mediatek.com
Signed-off-by: Greg Kroah-Hartman <gregkh@...uxfoundation.org>
---
 drivers/usb/typec/altmodes/displayport.c |    4 ++--
 include/linux/usb/typec_dp.h             |    5 +++++
 2 files changed, 7 insertions(+), 2 deletions(-)

--- a/drivers/usb/typec/altmodes/displayport.c
+++ b/drivers/usb/typec/altmodes/displayport.c
@@ -88,8 +88,8 @@ static int dp_altmode_configure(struct d
 	case DP_STATUS_CON_UFP_D:
 	case DP_STATUS_CON_BOTH: /* NOTE: First acting as DP source */
 		conf |= DP_CONF_UFP_U_AS_UFP_D;
-		pin_assign = DP_CAP_DFP_D_PIN_ASSIGN(dp->alt->vdo) &
-			     DP_CAP_UFP_D_PIN_ASSIGN(dp->port->vdo);
+		pin_assign = DP_CAP_PIN_ASSIGN_UFP_D(dp->alt->vdo) &
+				 DP_CAP_PIN_ASSIGN_DFP_D(dp->port->vdo);
 		break;
 	default:
 		break;
--- a/include/linux/usb/typec_dp.h
+++ b/include/linux/usb/typec_dp.h
@@ -73,6 +73,11 @@ enum {
 #define DP_CAP_USB			BIT(7)
 #define DP_CAP_DFP_D_PIN_ASSIGN(_cap_)	(((_cap_) & GENMASK(15, 8)) >> 8)
 #define DP_CAP_UFP_D_PIN_ASSIGN(_cap_)	(((_cap_) & GENMASK(23, 16)) >> 16)
+/* Get pin assignment taking plug & receptacle into consideration */
+#define DP_CAP_PIN_ASSIGN_UFP_D(_cap_) ((_cap_ & DP_CAP_RECEPTACLE) ? \
+			DP_CAP_UFP_D_PIN_ASSIGN(_cap_) : DP_CAP_DFP_D_PIN_ASSIGN(_cap_))
+#define DP_CAP_PIN_ASSIGN_DFP_D(_cap_) ((_cap_ & DP_CAP_RECEPTACLE) ? \
+			DP_CAP_DFP_D_PIN_ASSIGN(_cap_) : DP_CAP_UFP_D_PIN_ASSIGN(_cap_))
 
 /* DisplayPort Status Update VDO bits */
 #define DP_STATUS_CONNECTION(_status_)	((_status_) & 3)