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Commit 08f27a24 authored by Pablo Sun's avatar Pablo Sun Committed by Greg Kroah-Hartman
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usb: typec: altmodes/displayport: correct pin assignment for UFP receptacles 



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: 0e3bb7d6 ("usb: typec: Add driver for DisplayPort alternate mode")
Cc: stable@vger.kernel.org
Co-developed-by: default avatarPablo Sun <pablo.sun@mediatek.com>
Co-developed-by: default avatarMacpaul Lin <macpaul.lin@mediatek.com>
Reviewed-by: default avatarGuillaume Ranquet <granquet@baylibre.com>
Reviewed-by: default avatarHeikki Krogerus <heikki.krogerus@linux.intel.com>
Signed-off-by: default avatarPablo Sun <pablo.sun@mediatek.com>
Signed-off-by: default avatarMacpaul Lin <macpaul.lin@mediatek.com>
Link: https://lore.kernel.org/r/20220804034803.19486-1-macpaul.lin@mediatek.com


Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 1abdc68b

drivers/usb/typec/altmodes/displayport.c

+2 −2
Original line number Diff line number Diff line
@@ -87,8 +87,8 @@ static int dp_altmode_configure(struct dp_altmode *dp, u8 con) 
	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;

include/linux/usb/typec_dp.h

+5 −0
Original line number Diff line number Diff line
@@ -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)