[PATCH AUTOSEL 5.18 10/68] thunderbolt: Use different lane for second DisplayPort tunnel

From: Sasha Levin
Date: Tue Jun 07 2022 - 15:07:13 EST

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From: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>

[ Upstream commit 9d2d0a5cf0ca063f417681cc33e767ce52615286 ]

Brad reported that on Apple hardware with Light Ridge or Falcon Ridge
controller, plugging in a chain of Thunderbolt displays (Light Ridge
based controllers) causes all kinds of tearing and flickering. The
reason for this is that on Thunderbolt 1 hardware there is no lane
bonding so we have two independent 10 Gb/s lanes, and currently Linux
tunnels both displays through the lane 1. This makes the displays to
share the 10 Gb/s bandwidth which may not be enough for higher
resolutions.

For this reason make the second tunnel go through the lane 0 instead.
This seems to match what the macOS connection manager is also doing.

Reported-by: Brad Campbell <lists2009@xxxxxxxxxxxxxxx>
Signed-off-by: Mika Westerberg <mika.westerberg@xxxxxxxxxxxxxxx>
Tested-by: Brad Campbell <lists2009@xxxxxxxxxxxxxxx>
Signed-off-by: Sasha Levin <sashal@xxxxxxxxxx>
---
drivers/thunderbolt/tb.c | 19 +++++++++++++++++--
drivers/thunderbolt/test.c | 16 ++++++++--------
drivers/thunderbolt/tunnel.c | 11 ++++++-----
drivers/thunderbolt/tunnel.h | 4 ++--
4 files changed, 33 insertions(+), 17 deletions(-)

diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 9beb47b31c75..44d04b651a8b 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -867,7 +867,7 @@ static struct tb_port *tb_find_dp_out(struct tb *tb, struct tb_port *in)

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;
@@ -912,6 +912,20 @@ 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.
@@ -943,7 +957,8 @@ static void tb_tunnel_dp(struct tb *tb)
tb_dbg(tb, "available bandwidth for new DP tunnel %u/%u Mb/s\n",
available_up, available_down);

- 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_reclaim;
diff --git a/drivers/thunderbolt/test.c b/drivers/thunderbolt/test.c
index 1f69bab236ee..66b6e665e96f 100644
--- a/drivers/thunderbolt/test.c
+++ b/drivers/thunderbolt/test.c
@@ -1348,7 +1348,7 @@ 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);
@@ -1394,7 +1394,7 @@ 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);
@@ -1444,7 +1444,7 @@ 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);
@@ -1509,7 +1509,7 @@ 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);
@@ -1627,7 +1627,7 @@ 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));
@@ -2009,7 +2009,7 @@ 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);

@@ -2245,7 +2245,7 @@ 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);

@@ -2282,7 +2282,7 @@ 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 118742ec93ed..8ccd70920b6a 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -858,6 +858,7 @@ 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
@@ -869,8 +870,8 @@ 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;
@@ -894,21 +895,21 @@ 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 03e56076b5bc..bb4d1f1d6d0b 100644
--- a/drivers/thunderbolt/tunnel.h
+++ b/drivers/thunderbolt/tunnel.h
@@ -71,8 +71,8 @@ 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,
--
2.35.1

Next message: Sasha Levin: "[PATCH AUTOSEL 5.18 08/68] tty: synclink_gt: Fix null-pointer-dereference in slgt_clean()"
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