linux-kernel - [PATCH 1/3] usb: typec: tcpm: Correct the responses in SVDM Version 2.0 DFP

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Message-Id: <20210527084419.4164369-2-kyletso@google.com>
Date:   Thu, 27 May 2021 16:44:17 +0800
From:   Kyle Tso <kyletso@...gle.com>
To:     linux@...ck-us.net, heikki.krogerus@...ux.intel.com,
        gregkh@...uxfoundation.org, robh+dt@...nel.org
Cc:     badhri@...gle.com, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org, devicetree@...r.kernel.org,
        Kyle Tso <kyletso@...gle.com>
Subject: [PATCH 1/3] usb: typec: tcpm: Correct the responses in SVDM Version
 2.0 DFP

In USB PD Spec Rev 3.1 Ver 1.0, section "6.12.5 Applicability of
Structured VDM Commands", DFP is allowed and recommended to respond to
Discovery Identity with ACK. And in section "6.4.4.2.5.1 Commands other
than Attention", NAK should be returned only when receiving Messages
with invalid fields, Messages in wrong situation, or unrecognize
Messages.

Still keep the original design for SVDM Version 1.0 for backward
compatibilities.

Fixes: 193a68011fdc ("staging: typec: tcpm: Respond to Discover Identity commands")
Signed-off-by: Kyle Tso <kyletso@...gle.com>
---
 drivers/usb/typec/tcpm/tcpm.c | 14 ++++++++++----
 1 file changed, 10 insertions(+), 4 deletions(-)

diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index 9ce8c9af4da5..a1bf0dc5babf 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -1547,19 +1547,25 @@ static int tcpm_pd_svdm(struct tcpm_port *port, struct typec_altmode *adev,
 			if (PD_VDO_VID(p[0]) != USB_SID_PD)
 				break;
 
-			if (PD_VDO_SVDM_VER(p[0]) < svdm_version)
+			if (PD_VDO_SVDM_VER(p[0]) < svdm_version) {
 				typec_partner_set_svdm_version(port->partner,
 							       PD_VDO_SVDM_VER(p[0]));
+				svdm_version = PD_VDO_SVDM_VER(p[0]);
+			}
 
 			tcpm_ams_start(port, DISCOVER_IDENTITY);
-			/* 6.4.4.3.1: Only respond as UFP (device) */
-			if (port->data_role == TYPEC_DEVICE &&
+			/*
+			 * PD2.0 Spec 6.10.3: respond with NAK as DFP (data host)
+			 * PD3.1 Spec 6.4.4.2.5.1: respond with NAK if "invalid field" or
+			 * "wrong configuation" or "Unrecognized"
+			 */
+			if ((port->data_role == TYPEC_DEVICE || svdm_version >= SVDM_VER_2_0) &&
 			    port->nr_snk_vdo) {
 				/*
 				 * Product Type DFP and Connector Type are not defined in SVDM
 				 * version 1.0 and shall be set to zero.
 				 */
-				if (typec_get_negotiated_svdm_version(typec) < SVDM_VER_2_0)
+				if (svdm_version < SVDM_VER_2_0)
 					response[1] = port->snk_vdo[0] & ~IDH_DFP_MASK
 						      & ~IDH_CONN_MASK;
 				else
-- 
2.31.1.818.g46aad6cb9e-goog