[PATCH 2/5] thunderbolt: Verify PCIe adapters in detect state before setup PCIe tunnel

[Gil Fine <gil.fine@linux.intel.com>]

USB4 Connection Manager guide suggests making sure PCIe downstream and PCIe
upstream adapter is in Detect state, before set up a PCIe tunnel.

Add this step by checking LTSSM field in ADP_PCIE_CS_0 to follow the CM
guide more closely.

Signed-off-by: Gil Fine <gil.fine@linux.intel.com>
---
 drivers/thunderbolt/tb.h      |  2 ++
 drivers/thunderbolt/tb_regs.h | 15 +++++++++++++++
 drivers/thunderbolt/tunnel.c  | 17 +++++++++++++++++
 drivers/thunderbolt/usb4.c    | 23 +++++++++++++++++++++++
 4 files changed, 57 insertions(+)

diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index c2ff2069eb20..dbbbd2bd63f3 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -1480,6 +1480,8 @@ int usb4_dp_port_allocate_bandwidth(struct tb_port *port, int bw);
 int usb4_dp_port_requested_bandwidth(struct tb_port *port);
 
 int usb4_pci_port_set_ext_encapsulation(struct tb_port *port, bool enable);
+int usb4_pci_port_check_ltssm_state(struct tb_port *port,
+				    enum tb_pcie_ltssm_state ltssm);
 
 static inline bool tb_is_usb4_port_device(const struct device *dev)
 {
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index c0bf136236e6..71bed02a6974 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -473,10 +473,25 @@ struct tb_regs_port_header {
 
 /* PCIe adapter registers */
 #define ADP_PCIE_CS_0				0x00
+#define ADP_PCIE_CS_0_LTSSM_MASK		GENMASK(28, 25)
 #define ADP_PCIE_CS_0_PE			BIT(31)
 #define ADP_PCIE_CS_1				0x01
 #define ADP_PCIE_CS_1_EE			BIT(0)
 
+enum tb_pcie_ltssm_state {
+	TB_PCIE_LTSSM_DETECT		= 0x0,
+	TB_PCIE_LTSSM_POLLING		= 0x1,
+	TB_PCIE_LTSSM_CONFIG		= 0x2,
+	TB_PCIE_LTSSM_CONFIG_IDLE	= 0x3,
+	TB_PCIE_LTSSM_RECOVERY		= 0x4,
+	TB_PCIE_LTSSM_RECOVERY_IDLE	= 0x5,
+	TB_PCIE_LTSSM_L0		= 0x6,
+	TB_PCIE_LTSSM_L1		= 0x7,
+	TB_PCIE_LTSSM_L2		= 0x8,
+	TB_PCIE_LTSSM_DISABLED		= 0x9,
+	TB_PCIE_LTSSM_HOT_RESET		= 0xa,
+};
+
 /* USB adapter registers */
 #define ADP_USB3_CS_0				0x00
 #define ADP_USB3_CS_0_V				BIT(30)
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 28c1e5c062f3..72beaf99765f 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -296,6 +296,22 @@ static inline void tb_tunnel_changed(struct tb_tunnel *tunnel)
 			tunnel->src_port, tunnel->dst_port);
 }
 
+static int tb_pci_pre_activate(struct tb_tunnel *tunnel)
+{
+	struct tb_port *down = tunnel->src_port;
+	struct tb_port *up = tunnel->dst_port;
+	int ret;
+
+	if (!tb_switch_is_usb4(down->sw) || !tb_switch_is_usb4(up->sw))
+		return 0;
+
+	ret = usb4_pci_port_check_ltssm_state(down, TB_PCIE_LTSSM_DETECT);
+	if (ret)
+		return ret;
+
+	return usb4_pci_port_check_ltssm_state(up, TB_PCIE_LTSSM_DETECT);
+}
+
 static int tb_pci_set_ext_encapsulation(struct tb_tunnel *tunnel, bool enable)
 {
 	struct tb_port *port = tb_upstream_port(tunnel->dst_port->sw);
@@ -511,6 +527,7 @@ struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
 	if (!tunnel)
 		return NULL;
 
+	tunnel->pre_activate = tb_pci_pre_activate;
 	tunnel->activate = tb_pci_activate;
 	tunnel->src_port = down;
 	tunnel->dst_port = up;
diff --git a/drivers/thunderbolt/usb4.c b/drivers/thunderbolt/usb4.c
index 403a46aa35e5..706c9bc796e2 100644
--- a/drivers/thunderbolt/usb4.c
+++ b/drivers/thunderbolt/usb4.c
@@ -3145,3 +3145,26 @@ int usb4_pci_port_set_ext_encapsulation(struct tb_port *port, bool enable)
 	return tb_port_write(port, &val, TB_CFG_PORT,
 			     port->cap_adap + ADP_PCIE_CS_1, 1);
 }
+
+/**
+ * usb4_pci_port_check_ltssm_state() - Checks the LTSSM state of PCIe adapter
+ * @port: PCIe adapter
+ * @ltssm: PCIe adapter LTSSM state as encoded in &enum tb_pcie_ltssm_state
+ *
+ * Return:
+ * * %0 - If LTSSM state of @port is as expected @state.
+ * * %-ETIMEDOUT - The @ltssm state was not reached within the given timeout.
+ * * Negative errno - Other failure occurred.
+ */
+int usb4_pci_port_check_ltssm_state(struct tb_port *port,
+				    enum tb_pcie_ltssm_state ltssm)
+{
+	u32 val = FIELD_PREP(ADP_PCIE_CS_0_LTSSM_MASK, ltssm);
+
+	if (!tb_port_is_pcie_down(port) && !tb_port_is_pcie_up(port))
+		return -EINVAL;
+
+	return usb4_port_wait_for_bit(port, port->cap_adap + ADP_PCIE_CS_0,
+				      ADP_PCIE_CS_0_LTSSM_MASK, val, 500,
+				      USB4_PORT_DELAY);
+}
-- 
2.43.0