soc/intel/common: Add support for AP initiated mode entry

Add support for AP initiated mode entry. The code flow has been
optimized as below -

Code flow when AP initiated mode entry is disabled:
          +-------+
          | Start |
          +---+---+
              |
              |
    +---------+---------+
    |wait_for_connection|
    |   Is DP ALT mode  |
    |     available?    |
    +---------+---------+
              |
              +--------------->-------+
           Yes|                 No    |
    +---------+---------+             |
    |Skip enter_dp_mode |             |
    +---------+---------+             |
              |                       |
              |                       |
  +-----------+----------+            |
  |wait_for_dp_mode_entry|            |
  |   Is DP flag set?    |            |
  +-----------+----------+            |
              |                       |
              +--------------->--------
           Yes|                 No    |
  +-----------+----------+            |
  |     wait_for_hpd     |            |
  | Is HPD_LVL flag set? |            |
  +-----------+----------+            |
              |                       |
              +--------------->--------
           Yes|                 No    |
  +-----------+----------+            |
  |    Rest of the code  |            |
  +-----------+----------+            |
              |                       |
              +---------------<-------+
              |
          +---+---+
          |  End  |
          +-------+

Code flow when AP initiated mode entry is enabled:
          +-------+
          | Start |
          +---+---+
              |
 +------------+-----------+
 |Skip wait_for_connection|
 +------------+-----------+
              |
     +--------+-------+
     |  enter_dp_mode |
     | Is USB device? |
     +--------+-------+
              |
              +--------------->-------+
           Yes|                 No    |
    +---------+---------+             |
    |   enter_dp_mode   |             |
    |    Send DP mode   |             |
    |   entry command   |             |
    +---------+---------+             |
              |                       |
  +-----------+----------+            |
  |wait_for_dp_mode_entry|            |
  |   Is DP flag set?    |            |
  |  (If not, loop wait  |            |
  |   until timed out)   |            |
  +-----------+----------+            |
              |                       |
              +--------------->--------
           Yes|                 No    |
  +-----------+----------+            |
  |     wait_for_hpd     |            |
  | Is HPD_LVL flag set? |            |
  |  (If not, loop wait  |            |
  |   until timed out)   |            |
  +-----------+----------+            |
              |                       |
              +--------------->--------
           Yes|                 No    |
  +-----------+----------+            |
  |    Rest of the code  |            |
  +-----------+----------+            |
              |                       |
              +---------------<-------+
              |
          +---+---+
          |  End  |
          +-------+

BUG=b:247670186
TEST=Verify display over TCSS and its impact on boot time for
google/rex

Time taken by enter_dp_mode / wait_for_dp+hpd / MultiPhaseSiInit
functions with this patch train:

1. When AP Mode entry is enabled
- With type-c display on C1 and SuzyQ on C0: 6.9ms / 420ms / 616ms
- With USB key on C1 and SuzyQ on C0       : 6.0ms / 505ms / 666ms
- Without any device on C1 and SuzyQ on C0 : 3.7ms /   0ms / 178ms

2. When AP Mode entry is disabled
- With type-c display on C1 and SuzyQ on C0: 1.7ms / 2.5ms / 213ms
- With USB key on C1 and SuzyQ on C0       : 0.9ms / 3.3ms / 177ms
- Without any device on C1 and SuzyQ on C0 : 0.8ms / 1.8ms / 165ms

Without this patch train, wait_for_hpd would cause a constant delay of
WAIT_FOR_HPD_TIMEOUT_MS (i.e. 3 seconds) per type-c port when there is
no device connected.

Signed-off-by: Kapil Porwal <kapilporwal@google.com>
Change-Id: I514ccbdbaf905c49585dc00746d047554d7c7a58
Reviewed-on: https://review.coreboot.org/c/coreboot/+/76366
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Eric Lai <eric_lai@quanta.corp-partner.google.com>
Reviewed-by: Subrata Banik <subratabanik@google.com>

src/soc/intel/common/block/tcss/tcss.c

@@ -20,6 +20,9 @@
 
 #define BIAS_CTRL_VW_INDEX_SHIFT		16
 #define BIAS_CTRL_BIT_POS_SHIFT			8
+#define WAIT_FOR_DISPLAYPORT_TIMEOUT_MS		1000
+#define WAIT_FOR_DP_MODE_ENTRY_TIMEOUT_MS	500
+#define WAIT_FOR_HPD_TIMEOUT_MS			3000
 
 static uint32_t tcss_make_conn_cmd(int u, int u3, int u2, int ufp, int hsl,
 					int sbu, int acc)
@@ -277,7 +280,7 @@ static void tcss_init_mux(int port, const struct tcss_port_map *port_map)
 
 static void tcss_configure_dp_mode(const struct tcss_port_map *port_map, size_t num_ports)
 {
-	int ret;
+	int ret, port_bitmask;
 	size_t i;
 	const struct usbc_ops *ops;
 	struct usbc_mux_info mux_info;
@@ -290,9 +293,28 @@ static void tcss_configure_dp_mode(const struct tcss_port_map *port_map, size_t
 	if (ops == NULL)
 		return;
 
+	port_bitmask = ops->dp_ops.wait_for_connection(WAIT_FOR_DISPLAYPORT_TIMEOUT_MS);
+	if (!port_bitmask)	/* No DP device is connected */
+		return;
+
 	for (i = 0; i < num_ports; i++) {
+		if (!(port_bitmask & BIT(i)))
+			continue;
+
+		ret = ops->dp_ops.enter_dp_mode(i);
+		if (ret < 0)
+			continue;
+
+		ret = ops->dp_ops.wait_for_dp_mode_entry(i, WAIT_FOR_DP_MODE_ENTRY_TIMEOUT_MS);
+		if (ret < 0)
+			continue;
+
+		ret = ops->dp_ops.wait_for_hpd(i, WAIT_FOR_HPD_TIMEOUT_MS);
+		if (ret < 0)
+			continue;
+
 		ret = ops->mux_ops.get_mux_info(i, &mux_info);
-		if ((ret < 0) || (!mux_info.dp))
+		if (ret < 0)
 			continue;
 
 		port_info = &port_map[i];