[PATCH v4 30/36] thunderbolt: Add support for DMA tunnels

[Mika Westerberg]

In addition to PCIe and Display Port tunnels it is also possible to
create tunnels that forward DMA traffic from the host interface adapter
(NHI) to a NULL port that is connected to another domain through a
Thunderbolt cable. These tunnels can be used to carry software messages
such as networking packets.

To support this we introduce another tunnel type (TB_TUNNEL_DMA) that
supports paths from NHI to NULL port and back.

Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
---
 drivers/thunderbolt/path.c    | 22 +++++++--
 drivers/thunderbolt/switch.c  | 22 +++++++++
 drivers/thunderbolt/tb.h      |  4 ++
 drivers/thunderbolt/tb_regs.h |  3 ++
 drivers/thunderbolt/tunnel.c  | 93 ++++++++++++++++++++++++++++++++++-
 drivers/thunderbolt/tunnel.h  | 10 ++++
 6 files changed, 149 insertions(+), 5 deletions(-)

diff --git a/drivers/thunderbolt/path.c b/drivers/thunderbolt/path.c
index 3fc92881a197..e4c22f53ef4d 100644
--- a/drivers/thunderbolt/path.c
+++ b/drivers/thunderbolt/path.c
@@ -341,7 +341,8 @@ static void __tb_path_deallocate_nfc(struct tb_path *path, int first_hop)
 	}
 }
 
-static int __tb_path_deactivate_hop(struct tb_port *port, int hop_index)
+static int __tb_path_deactivate_hop(struct tb_port *port, int hop_index,
+				    bool clear_fc)
 {
 	struct tb_regs_hop hop;
 	ktime_t timeout;
@@ -369,8 +370,20 @@ static int __tb_path_deactivate_hop(struct tb_port *port, int hop_index)
 		if (ret)
 			return ret;
 
-		if (!hop.pending)
+		if (!hop.pending) {
+			if (clear_fc) {
+				/* Clear flow control */
+				hop.ingress_fc = 0;
+				hop.egress_fc = 0;
+				hop.ingress_shared_buffer = 0;
+				hop.egress_shared_buffer = 0;
+
+				return tb_port_write(port, &hop, TB_CFG_HOPS,
+						     2 * hop_index, 2);
+			}
+
 			return 0;
+		}
 
 		usleep_range(10, 20);
 	} while (ktime_before(ktime_get(), timeout));
@@ -384,7 +397,8 @@ static void __tb_path_deactivate_hops(struct tb_path *path, int first_hop)
 
 	for (i = first_hop; i < path->path_length; i++) {
 		res = __tb_path_deactivate_hop(path->hops[i].in_port,
-					       path->hops[i].in_hop_index);
+					       path->hops[i].in_hop_index,
+					       path->clear_fc);
 		if (res && res != -ENODEV)
 			tb_port_warn(path->hops[i].in_port,
 				     "hop deactivation failed for hop %d, index %d\n",
@@ -459,7 +473,7 @@ int tb_path_activate(struct tb_path *path)
 
 		/* If it is left active deactivate it first */
 		__tb_path_deactivate_hop(path->hops[i].in_port,
-				path->hops[i].in_hop_index);
+				path->hops[i].in_hop_index, path->clear_fc);
 
 		/* dword 0 */
 		hop.next_hop = path->hops[i].next_hop_index;
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 1de1afa24182..ecf53d986a5c 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -555,6 +555,28 @@ int tb_port_add_nfc_credits(struct tb_port *port, int credits)
 			     TB_CFG_PORT, 4, 1);
 }
 
+/**
+ * tb_port_set_initial_credits() - Set initial port link credits allocated
+ * @port: Port to set the initial credits
+ * @credits: Number of credits to to allocate
+ *
+ * Set initial credits value to be used for ingress shared buffering.
+ */
+int tb_port_set_initial_credits(struct tb_port *port, u32 credits)
+{
+	u32 data;
+	int ret;
+
+	ret = tb_port_read(port, &data, TB_CFG_PORT, 5, 1);
+	if (ret)
+		return ret;
+
+	data &= ~TB_PORT_LCA_MASK;
+	data |= (credits << TB_PORT_LCA_SHIFT) & TB_PORT_LCA_MASK;
+
+	return tb_port_write(port, &data, TB_CFG_PORT, 5, 1);
+}
+
 /**
  * tb_port_clear_counter() - clear a counter in TB_CFG_COUNTER
  *
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 89b5d18f6035..119a00837992 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -207,6 +207,8 @@ enum tb_path_port {
  * @weight: Weight of the path inside the priority group
  * @drop_packages: Drop packages from queue tail or head
  * @activated: Is the path active
+ * @clear_fc: Clear all flow control from the path config space entries
+ *	      when deactivating this path
  * @hops: Path hops
  * @path_length: How many hops the path uses
  *
@@ -227,6 +229,7 @@ struct tb_path {
 	int weight:4;
 	bool drop_packages;
 	bool activated;
+	bool clear_fc;
 	struct tb_path_hop *hops;
 	int path_length;
 };
@@ -583,6 +586,7 @@ static inline bool tb_switch_is_fr(const struct tb_switch *sw)
 
 int tb_wait_for_port(struct tb_port *port, bool wait_if_unplugged);
 int tb_port_add_nfc_credits(struct tb_port *port, int credits);
+int tb_port_set_initial_credits(struct tb_port *port, u32 credits);
 int tb_port_clear_counter(struct tb_port *port, int counter);
 int tb_port_alloc_in_hopid(struct tb_port *port, int hopid, int max_hopid);
 void tb_port_release_in_hopid(struct tb_port *port, int hopid);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index 3ce705184e2c..deb9d4a977b9 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -215,6 +215,9 @@ struct tb_regs_port_header {
 #define TB_PORT_NFC_CREDITS_MASK	GENMASK(19, 0)
 #define TB_PORT_MAX_CREDITS_SHIFT	20
 #define TB_PORT_MAX_CREDITS_MASK	GENMASK(26, 20)
+/* DWORD 5 */
+#define TB_PORT_LCA_SHIFT		22
+#define TB_PORT_LCA_MASK		GENMASK(28, 22)
 
 /* Display Port adapter registers */
 
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 0bc6639c6e74..9f9b26b12d0a 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -27,7 +27,10 @@
 #define TB_DP_AUX_PATH_OUT		1
 #define TB_DP_AUX_PATH_IN		2
 
-static const char * const tb_tunnel_names[] = { "PCI", "DP" };
+#define TB_DMA_PATH_OUT			0
+#define TB_DMA_PATH_IN			1
+
+static const char * const tb_tunnel_names[] = { "PCI", "DP", "DMA" };
 
 #define __TB_TUNNEL_PRINT(level, tunnel, fmt, arg...)                   \
 	do {                                                            \
@@ -471,6 +474,94 @@ struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
 	return NULL;
 }
 
+static u32 tb_dma_credits(struct tb_port *nhi)
+{
+	u32 max_credits;
+
+	max_credits = (nhi->config.nfc_credits & TB_PORT_MAX_CREDITS_MASK) >>
+		TB_PORT_MAX_CREDITS_SHIFT;
+	return min(max_credits, 13U);
+}
+
+static int tb_dma_activate(struct tb_tunnel *tunnel, bool active)
+{
+	struct tb_port *nhi = tunnel->src_port;
+	u32 credits;
+
+	credits = active ? tb_dma_credits(nhi) : 0;
+	return tb_port_set_initial_credits(nhi, credits);
+}
+
+static void tb_dma_init_path(struct tb_path *path, unsigned int isb,
+			     unsigned int efc, u32 credits)
+{
+	int i;
+
+	path->egress_fc_enable = efc;
+	path->ingress_fc_enable = TB_PATH_ALL;
+	path->egress_shared_buffer = TB_PATH_NONE;
+	path->ingress_shared_buffer = isb;
+	path->priority = 5;
+	path->weight = 1;
+	path->clear_fc = true;
+
+	for (i = 0; i < path->path_length; i++)
+		path->hops[i].initial_credits = credits;
+}
+
+/**
+ * tb_tunnel_alloc_dma() - allocate a DMA tunnel
+ * @tb: Pointer to the domain structure
+ * @nhi: Host controller port
+ * @dst: Destination null port which the other domain is connected to
+ * @transmit_ring: NHI ring number used to send packets towards the
+ *		   other domain
+ * @transmit_path: HopID used for transmitting packets
+ * @receive_ring: NHI ring number used to receive packets from the
+ *		  other domain
+ * @reveive_path: HopID used for receiving packets
+ *
+ * Return: Returns a tb_tunnel on success or NULL on failure.
+ */
+struct tb_tunnel *tb_tunnel_alloc_dma(struct tb *tb, struct tb_port *nhi,
+				      struct tb_port *dst, int transmit_ring,
+				      int transmit_path, int receive_ring,
+				      int receive_path)
+{
+	struct tb_tunnel *tunnel;
+	struct tb_path *path;
+	u32 credits;
+
+	tunnel = tb_tunnel_alloc(tb, 2, TB_TUNNEL_DMA);
+	if (!tunnel)
+		return NULL;
+
+	tunnel->activate = tb_dma_activate;
+	tunnel->src_port = nhi;
+	tunnel->dst_port = dst;
+
+	credits = tb_dma_credits(nhi);
+
+	path = tb_path_alloc(tb, dst, receive_path, nhi, receive_ring, 0, "DMA RX");
+	if (!path) {
+		tb_tunnel_free(tunnel);
+		return NULL;
+	}
+	tb_dma_init_path(path, TB_PATH_NONE, TB_PATH_SOURCE | TB_PATH_INTERNAL,
+			 credits);
+	tunnel->paths[TB_DMA_PATH_IN] = path;
+
+	path = tb_path_alloc(tb, nhi, transmit_ring, dst, transmit_path, 0, "DMA TX");
+	if (!path) {
+		tb_tunnel_free(tunnel);
+		return NULL;
+	}
+	tb_dma_init_path(path, TB_PATH_SOURCE, TB_PATH_ALL, credits);
+	tunnel->paths[TB_DMA_PATH_OUT] = path;
+
+	return tunnel;
+}
+
 /**
  * tb_tunnel_free() - free a tunnel
  * @tunnel: Tunnel to be freed
diff --git a/drivers/thunderbolt/tunnel.h b/drivers/thunderbolt/tunnel.h
index 0373779f43ba..c68bbcd3a62c 100644
--- a/drivers/thunderbolt/tunnel.h
+++ b/drivers/thunderbolt/tunnel.h
@@ -14,6 +14,7 @@
 enum tb_tunnel_type {
 	TB_TUNNEL_PCI,
 	TB_TUNNEL_DP,
+	TB_TUNNEL_DMA,
 };
 
 /**
@@ -47,6 +48,10 @@ struct tb_tunnel *tb_tunnel_alloc_pci(struct tb *tb, struct tb_port *up,
 struct tb_tunnel *tb_tunnel_discover_dp(struct tb *tb, struct tb_port *in);
 struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
 				     struct tb_port *out);
+struct tb_tunnel *tb_tunnel_alloc_dma(struct tb *tb, struct tb_port *nhi,
+				      struct tb_port *dst, int transmit_ring,
+				      int transmit_path, int receive_ring,
+				      int receive_path);
 
 void tb_tunnel_free(struct tb_tunnel *tunnel);
 int tb_tunnel_activate(struct tb_tunnel *tunnel);
@@ -64,5 +69,10 @@ static inline bool tb_tunnel_is_dp(const struct tb_tunnel *tunnel)
 	return tunnel->type == TB_TUNNEL_DP;
 }
 
+static inline bool tb_tunnel_is_dma(const struct tb_tunnel *tunnel)
+{
+	return tunnel->type == TB_TUNNEL_DMA;
+}
+
 #endif
 
-- 
2.20.1