[RFC PATCH 12/22] thunderbolt: Add Display Port CM handshake for Titan Ridge devices

From: Mika Westerberg <mika.westerberg@linux.intel.com>
To: linux-usb@vger.kernel.org
Cc: Andreas Noever <andreas.noever@gmail.com>,
	Michael Jamet <michael.jamet@intel.com>,
	Mika Westerberg <mika.westerberg@linux.intel.com>,
	Yehezkel Bernat <YehezkelShB@gmail.com>,
	Rajmohan Mani <rajmohan.mani@intel.com>,
	Nicholas Johnson <nicholas.johnson-opensource@outlook.com.au>,
	Lukas Wunner <lukas@wunner.de>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	Alan Stern <stern@rowland.harvard.edu>,
	Mario.Limonciello@dell.com,
	Anthony Wong <anthony.wong@canonical.com>,
	linux-kernel@vger.kernel.org
Subject: [RFC PATCH 12/22] thunderbolt: Add Display Port CM handshake for Titan Ridge devices
Date: Tue,  1 Oct 2019 14:38:20 +0300	[thread overview]
Message-ID: <20191001113830.13028-13-mika.westerberg@linux.intel.com> (raw)
In-Reply-To: <20191001113830.13028-1-mika.westerberg@linux.intel.com>

Titan Ridge devices and newer need an additional connection manager
handshake in order to do proper Display Port tunneling so implement it
here.

Signed-off-by: Mika Westerberg <mika.westerberg@linux.intel.com>
---
 drivers/thunderbolt/tb_regs.h |  3 +++
 drivers/thunderbolt/tunnel.c  | 44 +++++++++++++++++++++++++++++++++++
 2 files changed, 47 insertions(+)

diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 3a39490a954b..8d11b4a2d552 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -252,6 +252,9 @@ struct tb_regs_port_header {
 #define ADP_DP_CS_3_HDPC			BIT(9)
 #define DP_LOCAL_CAP				0x04
 #define DP_REMOTE_CAP				0x05
+#define DP_STATUS_CTRL				0x06
+#define DP_STATUS_CTRL_CMHS			BIT(25)
+#define DP_STATUS_CTRL_UF			BIT(26)
 
 /* PCIe adapter registers */
 #define ADP_PCIE_CS_0				0x00
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 3353396e0806..369800110e5e 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -6,6 +6,7 @@
  * Copyright (C) 2019, Intel Corporation
  */
 
+#include <linux/delay.h>
 #include <linux/slab.h>
 #include <linux/list.h>
 
@@ -242,6 +243,41 @@ struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
 	return tunnel;
 }
 
+static int tb_dp_cm_handshake(struct tb_port *in, struct tb_port *out)
+{
+	int timeout = 10;
+	u32 val;
+	int ret;
+
+	/* Both ends need to support this */
+	if (!tb_switch_is_tr(in->sw) || !tb_switch_is_tr(out->sw))
+		return 0;
+
+	ret = tb_port_read(out, &val, TB_CFG_PORT,
+			   out->cap_adap + DP_STATUS_CTRL, 1);
+	if (ret)
+		return ret;
+
+	val |= DP_STATUS_CTRL_UF | DP_STATUS_CTRL_CMHS;
+
+	ret = tb_port_write(out, &val, TB_CFG_PORT,
+			    out->cap_adap + DP_STATUS_CTRL, 1);
+	if (ret)
+		return ret;
+
+	do {
+		ret = tb_port_read(out, &val, TB_CFG_PORT,
+				   out->cap_adap + DP_STATUS_CTRL, 1);
+		if (ret)
+			return ret;
+		if (!(val & DP_STATUS_CTRL_CMHS))
+			return 0;
+		usleep_range(10, 100);
+	} while (timeout--);
+
+	return -ETIMEDOUT;
+}
+
 static int tb_dp_xchg_caps(struct tb_tunnel *tunnel)
 {
 	struct tb_port *out = tunnel->dst_port;
@@ -256,6 +292,14 @@ static int tb_dp_xchg_caps(struct tb_tunnel *tunnel)
 	if (in->sw->generation < 2 || out->sw->generation < 2)
 		return 0;
 
+	/*
+	 * Perform connection manager handshake between IN and OUT ports
+	 * before capabilities exchange can take place.
+	 */
+	ret = tb_dp_cm_handshake(in, out);
+	if (ret)
+		return ret;
+
 	/* Read both DP_LOCAL_CAP registers */
 	ret = tb_port_read(in, &in_dp_cap, TB_CFG_PORT,
 			   in->cap_adap + DP_LOCAL_CAP, 1);
-- 
2.23.0

