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SubjectRe: Apple Thunderbolt Display chaining
Hi,

On Tue, Aug 09, 2022 at 11:16:27PM +0800, Brad Campbell wrote:
> If I then reboot and load the driver it fails.
>
> The only thing I could think of doing was an lspci -vvv after the boot and module load
> and an lspci -vvv after a warm reboot and diff them, because there are changes around the
> thunderbolt bridge devices. I've done a diff -u50 to try and keep as much context as possible.
>
> On the first boot I can unload/reload the thunderbolt module repeatedly and there's no issue
> but loading it after a reboot locks up. There are no lspci changes on the first boot after the
> initial module load unless I rescan the PCI bus, but they're minor and it doesn't cause an issue
> with loading the thunderbolt module.
>
> The firmware *must* be doing something on reboot I suppose or the PCIe configs wouldn't change.

Okay, let's try a bigger hammer and reset all the ports upon load. That
should hopefully clear out the "bad state" too. This is completely
untested but it should trigger reset and then re-initialize the TBT
links.

diff --git a/drivers/thunderbolt/lc.c b/drivers/thunderbolt/lc.c
index 633970fbe9b0..c419c2568de4 100644
--- a/drivers/thunderbolt/lc.c
+++ b/drivers/thunderbolt/lc.c
@@ -6,6 +6,8 @@
* Author: Mika Westerberg <mika.westerberg@linux.intel.com>
*/

+#include <linux/delay.h>
+
#include "tb.h"

/**
@@ -327,6 +329,34 @@ void tb_lc_xhci_disconnect(struct tb_port *port)
tb_port_dbg(port, "xHCI disconnected\n");
}

+int tb_lc_reset_port(struct tb_port *port)
+{
+ struct tb_switch *sw = port->sw;
+ int cap, ret;
+ u32 val;
+
+ if (sw->generation != 3)
+ return -EINVAL;
+
+ cap = find_port_lc_cap(port);
+ if (cap < 0)
+ return cap;
+
+ ret = tb_sw_read(sw, &val, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+ if (ret)
+ return ret;
+
+ val |= TB_LC_PORT_MODE_DPR;
+ ret = tb_sw_write(sw, &val, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+ if (ret)
+ return ret;
+
+ msleep(20);
+
+ val &= ~TB_LC_PORT_MODE_DPR;
+ return tb_sw_write(sw, &val, TB_CFG_SWITCH, cap + TB_LC_PORT_MODE, 1);
+}
+
static int tb_lc_set_wake_one(struct tb_switch *sw, unsigned int offset,
unsigned int flags)
{
diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 0ae8a7ec7c9c..21ac3ccf1cf9 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -740,6 +740,11 @@ int tb_port_disable(struct tb_port *port)
return __tb_port_enable(port, false);
}

+int tb_port_reset(struct tb_port *port)
+{
+ return tb_lc_reset_port(port);
+}
+
/*
* tb_init_port() - initialize a port
*
diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index 8030fc544c5e..48a7396994ef 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -1875,6 +1875,7 @@ static int tb_scan_finalize_switch(struct device *dev, void *data)
static int tb_start(struct tb *tb)
{
struct tb_cm *tcm = tb_priv(tb);
+ struct tb_port *p;
int ret;

tb->root_switch = tb_switch_alloc(tb, &tb->dev, 0);
@@ -1911,6 +1912,12 @@ static int tb_start(struct tb *tb)
false);
/* Enable TMU if it is off */
tb_switch_tmu_enable(tb->root_switch);
+
+ tb_switch_for_each_port(tb->root_switch, p) {
+ if (tb_port_is_null(p))
+ tb_port_reset(p);
+ }
+
/* Full scan to discover devices added before the driver was loaded. */
tb_scan_switch(tb->root_switch);
/* Find out tunnels created by the boot firmware */
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 28bb80d967d6..fe5edefec712 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -1028,6 +1028,7 @@ int tb_port_clear_counter(struct tb_port *port, int counter);
int tb_port_unlock(struct tb_port *port);
int tb_port_enable(struct tb_port *port);
int tb_port_disable(struct tb_port *port);
+int tb_port_reset(struct tb_port *port);
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);
int tb_port_alloc_out_hopid(struct tb_port *port, int hopid, int max_hopid);
@@ -1121,6 +1122,7 @@ bool tb_lc_is_usb_plugged(struct tb_port *port);
bool tb_lc_is_xhci_connected(struct tb_port *port);
int tb_lc_xhci_connect(struct tb_port *port);
void tb_lc_xhci_disconnect(struct tb_port *port);
+int tb_lc_reset_port(struct tb_port *port);
int tb_lc_set_wake(struct tb_switch *sw, unsigned int flags);
int tb_lc_set_sleep(struct tb_switch *sw);
bool tb_lc_lane_bonding_possible(struct tb_switch *sw);
diff --git a/drivers/thunderbolt/tb_regs.h b/drivers/thunderbolt/tb_regs.h
index f8c1ca3464d9..8fd12bc2d500 100644
--- a/drivers/thunderbolt/tb_regs.h
+++ b/drivers/thunderbolt/tb_regs.h
@@ -555,6 +555,9 @@ struct tb_regs_hop {
#define TB_LC_POWER 0x740

/* Link controller registers */
+#define TB_LC_PORT_MODE 0x26
+#define TB_LC_PORT_MODE_DPR BIT(6)
+
#define TB_LC_CS_42 0x2a
#define TB_LC_CS_42_USB_PLUGGED BIT(31)

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