[PATCH 07/19] thunderbolt: Don't read the UID if we already know it

[Sven Peter]

On Apple Silicon the host router's UID comes from the DROM provided by
the device tree and is already known by the time tb_switch_set_uuid()
runs. Skip reading it from the config space again in that case.

For other USB4 hosts this only drops a duplicate read because
tb_drom_host_read() has already filled in the UID from ROUTER_CS_7
before tb_switch_set_uuid() runs. Device routers keep reading it
unconditionally.

Signed-off-by: Sven Peter <sven at kernel.org>
---
 drivers/thunderbolt/switch.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/drivers/thunderbolt/switch.c b/drivers/thunderbolt/switch.c
index 404c0693df50..3f54a5ae56b0 100644
--- a/drivers/thunderbolt/switch.c
+++ b/drivers/thunderbolt/switch.c
@@ -2692,9 +2692,11 @@ static int tb_switch_set_uuid(struct tb_switch *sw)
 		return 0;
 
 	if (tb_switch_is_usb4(sw)) {
-		ret = usb4_switch_read_uid(sw, &sw->uid);
-		if (ret)
-			return ret;
+		if (tb_route(sw) || !sw->uid) {
+			ret = usb4_switch_read_uid(sw, &sw->uid);
+			if (ret)
+				return ret;
+		}
 		uid = true;
 	} else {
 		/*

-- 
2.55.0