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Date:   Fri, 1 Apr 2022 17:30:57 +0300
From:   Mika Westerberg <mika.westerberg@linux.intel.com>
To:     Brad Campbell <lists2009@fnarfbargle.com>
Cc:     linux-kernel@vger.kernel.org
Subject: Re: Apple Thunderbolt Display chaining
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Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo
Precedence: bulk

Hi,

On Fri, Apr 01, 2022 at 01:48:13PM +0800, Brad Campbell wrote:
> That I can do. I didn't crop or grep as I wasn't sure what might be additionally relevant.
> 2 machines, 2 ports, 4 cold boots. Each time just the Thnuderbolt displays chained.

Thanks for the logs! It looks like the Apple EFI CM always uses the lane
1 adapter.

Can you try the below patch? Fingers crossed that it solves the
chaining issue for both ;-) I had to patch the test.c because otherwise
unit tests fail to compile when enabled.

This should now setup the second tunnel always through the lane 0
adapter and thus share the bandwidth equally between the two lanes.

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 8c20a50cc9d9..1ca6fe67ba56 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1065,7 +1065,7 @@ static void tb_recalc_estimated_bandwidth(struct tb *tb)
 
 static void tb_tunnel_dp(struct tb *tb)
 {
-	int available_up, available_down, ret;
+	int available_up, available_down, ret, link_nr;
 	struct tb_cm *tcm = tb_priv(tb);
 	struct tb_port *port, *in, *out;
 	struct tb_tunnel *tunnel;
@@ -1110,6 +1110,20 @@ static void tb_tunnel_dp(struct tb *tb)
 		return;
 	}
 
+	/*
+	 * This is only applicable to links that are not bonded (so
+	 * when Thunderbolt 1 hardware is involved somewhere in the
+	 * topology). For these try to share the DP bandwidth between
+	 * the two lanes.
+	 */
+	link_nr = 1;
+	list_for_each_entry(tunnel, &tcm->tunnel_list, list) {
+		if (tb_tunnel_is_dp(tunnel)) {
+			link_nr = 0;
+			break;
+		}
+	}
+
 	/*
 	 * DP stream needs the domain to be active so runtime resume
 	 * both ends of the tunnel.
@@ -1142,7 +1156,8 @@ static void tb_tunnel_dp(struct tb *tb)
 
 	tb_attach_bandwidth_group(tcm, in, out);
 
-	tunnel = tb_tunnel_alloc_dp(tb, in, out, available_up, available_down);
+	tunnel = tb_tunnel_alloc_dp(tb, in, out, link_nr, available_up,
+				    available_down);
 	if (!tunnel) {
 		tb_port_dbg(out, "could not allocate DP tunnel\n");
 		goto err_detach_group;
diff --git a/drivers/thunderbolt/test.c b/drivers/thunderbolt/test.c
index 6f027b3c2efe..5884c616b047 100644
--- a/drivers/thunderbolt/test.c
+++ b/drivers/thunderbolt/test.c
@@ -1365,7 +1365,7 @@ static void tb_test_tunnel_dp(struct kunit *test)
 	in = &host->ports[5];
 	out = &dev->ports[13];
 
-	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel->src_port, in);
@@ -1411,7 +1411,7 @@ static void tb_test_tunnel_dp_chain(struct kunit *test)
 	in = &host->ports[5];
 	out = &dev4->ports[14];
 
-	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel->src_port, in);
@@ -1461,7 +1461,7 @@ static void tb_test_tunnel_dp_tree(struct kunit *test)
 	in = &dev2->ports[13];
 	out = &dev5->ports[13];
 
-	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel->src_port, in);
@@ -1526,7 +1526,7 @@ static void tb_test_tunnel_dp_max_length(struct kunit *test)
 	in = &dev6->ports[13];
 	out = &dev12->ports[13];
 
-	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel->src_port, in);
@@ -1604,7 +1604,7 @@ static void tb_test_tunnel_3dp(struct kunit *test)
 	KUNIT_ASSERT_EQ(test, tunnel1->npaths, 3);
 	KUNIT_ASSERT_EQ(test, tunnel1->paths[0]->path_length, 3);
 
-	tunnel2 = tb_tunnel_alloc_dp(NULL, in2, out2, 0, 0);
+	tunnel2 = tb_tunnel_alloc_dp(NULL, in2, out2, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel2 != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel2->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel2->src_port, in2);
@@ -1612,7 +1612,7 @@ static void tb_test_tunnel_3dp(struct kunit *test)
 	KUNIT_ASSERT_EQ(test, tunnel2->npaths, 3);
 	KUNIT_ASSERT_EQ(test, tunnel2->paths[0]->path_length, 4);
 
-	tunnel3 = tb_tunnel_alloc_dp(NULL, in3, out3, 0, 0);
+	tunnel3 = tb_tunnel_alloc_dp(NULL, in3, out3, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel3 != NULL);
 	KUNIT_EXPECT_EQ(test, tunnel3->type, TB_TUNNEL_DP);
 	KUNIT_EXPECT_PTR_EQ(test, tunnel3->src_port, in3);
@@ -1709,7 +1709,7 @@ static void tb_test_tunnel_port_on_path(struct kunit *test)
 	in = &dev2->ports[13];
 	out = &dev5->ports[13];
 
-	dp_tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	dp_tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, dp_tunnel != NULL);
 
 	KUNIT_EXPECT_TRUE(test, tb_tunnel_port_on_path(dp_tunnel, in));
@@ -2091,7 +2091,7 @@ static void tb_test_credit_alloc_dp(struct kunit *test)
 	in = &host->ports[5];
 	out = &dev->ports[14];
 
-	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	tunnel = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, tunnel != NULL);
 	KUNIT_ASSERT_EQ(test, tunnel->npaths, (size_t)3);
 
@@ -2327,7 +2327,7 @@ static struct tb_tunnel *TB_TEST_DP_TUNNEL1(struct kunit *test,
 
 	in = &host->ports[5];
 	out = &dev->ports[13];
-	dp_tunnel1 = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	dp_tunnel1 = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, dp_tunnel1 != NULL);
 	KUNIT_ASSERT_EQ(test, dp_tunnel1->npaths, (size_t)3);
 
@@ -2364,7 +2364,7 @@ static struct tb_tunnel *TB_TEST_DP_TUNNEL2(struct kunit *test,
 
 	in = &host->ports[6];
 	out = &dev->ports[14];
-	dp_tunnel2 = tb_tunnel_alloc_dp(NULL, in, out, 0, 0);
+	dp_tunnel2 = tb_tunnel_alloc_dp(NULL, in, out, 1, 0, 0);
 	KUNIT_ASSERT_TRUE(test, dp_tunnel2 != NULL);
 	KUNIT_ASSERT_EQ(test, dp_tunnel2->npaths, (size_t)3);
 
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index d08441f36e7a..08fddd469ab6 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -1086,6 +1086,7 @@ struct tb_tunnel *tb_tunnel_discover_dp(struct tb *tb, struct tb_port *in,
  * @tb: Pointer to the domain structure
  * @in: DP in adapter port
  * @out: DP out adapter port
+ * @link_nr: Preferred lane adapter when the link is not bonded
  * @max_up: Maximum available upstream bandwidth for the DP tunnel (%0
  *	    if not limited)
  * @max_down: Maximum available downstream bandwidth for the DP tunnel
@@ -1097,8 +1098,8 @@ struct tb_tunnel *tb_tunnel_discover_dp(struct tb *tb, struct tb_port *in,
  * Return: Returns a tb_tunnel on success or NULL on failure.
  */
 struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
-				     struct tb_port *out, int max_up,
-				     int max_down)
+				     struct tb_port *out, int link_nr,
+				     int max_up, int max_down)
 {
 	struct tb_tunnel *tunnel;
 	struct tb_path **paths;
@@ -1124,21 +1125,21 @@ struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
 	paths = tunnel->paths;
 
 	path = tb_path_alloc(tb, in, TB_DP_VIDEO_HOPID, out, TB_DP_VIDEO_HOPID,
-			     1, "Video");
+			     link_nr, "Video");
 	if (!path)
 		goto err_free;
 	tb_dp_init_video_path(path);
 	paths[TB_DP_VIDEO_PATH_OUT] = path;
 
 	path = tb_path_alloc(tb, in, TB_DP_AUX_TX_HOPID, out,
-			     TB_DP_AUX_TX_HOPID, 1, "AUX TX");
+			     TB_DP_AUX_TX_HOPID, link_nr, "AUX TX");
 	if (!path)
 		goto err_free;
 	tb_dp_init_aux_path(path);
 	paths[TB_DP_AUX_PATH_OUT] = path;
 
 	path = tb_path_alloc(tb, out, TB_DP_AUX_RX_HOPID, in,
-			     TB_DP_AUX_RX_HOPID, 1, "AUX RX");
+			     TB_DP_AUX_RX_HOPID, link_nr, "AUX RX");
 	if (!path)
 		goto err_free;
 	tb_dp_init_aux_path(path);
diff --git a/drivers/thunderbolt/tunnel.h b/drivers/thunderbolt/tunnel.h
index ea605046d41f..89d6328dd04f 100644
--- a/drivers/thunderbolt/tunnel.h
+++ b/drivers/thunderbolt/tunnel.h
@@ -77,8 +77,8 @@ 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,
 					bool alloc_hopid);
 struct tb_tunnel *tb_tunnel_alloc_dp(struct tb *tb, struct tb_port *in,
-				     struct tb_port *out, int max_up,
-				     int max_down);
+				     struct tb_port *out, int link_nr,
+				     int max_up, int max_down);
 struct tb_tunnel *tb_tunnel_alloc_dma(struct tb *tb, struct tb_port *nhi,
 				      struct tb_port *dst, int transmit_path,
 				      int transmit_ring, int receive_path,
-- 
2.32.0