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

From: Mika Westerberg
Date: Tue Oct 01 2019 - 07:38:47 EST


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@xxxxxxxxxxxxxxx>
---
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