From 7e49bb89df860bb7352974100cd5dd48752bb646 Mon Sep 17 00:00:00 2001 From: Gil Fine Date: Sun, 2 Nov 2025 23:58:34 +0200 Subject: [PATCH] thunderbolt: Avoid reserved fields in path config space for USB4 routers According to USB4 spec, USB4 Connection Manager shall not change value of any fields that are defined as "RsvdZ" or "VD". Specifically fields: Path Credits Allocated, IFC, ISE fields in path config space shall not be written by CM. To handle this, CM shall first read current path config space from the hardware, change only the fields that can be changed, and then write back the path config space. Signed-off-by: Gil Fine Signed-off-by: Mika Westerberg --- drivers/thunderbolt/path.c | 31 ++++++++++++++++++++++--------- 1 file changed, 22 insertions(+), 9 deletions(-) diff --git a/drivers/thunderbolt/path.c b/drivers/thunderbolt/path.c index 8713ea0f47c1b..0092b2ec7873f 100644 --- a/drivers/thunderbolt/path.c +++ b/drivers/thunderbolt/path.c @@ -412,7 +412,8 @@ static int __tb_path_deactivate_hop(struct tb_port *port, int hop_index, * in the USB4 spec so we clear them * only for pre-USB4 adapters. */ - if (!tb_switch_is_usb4(port->sw)) { + if (tb_port_is_null(port) || + !tb_switch_is_usb4(port->sw)) { hop.ingress_fc = 0; hop.ingress_shared_buffer = 0; } @@ -532,15 +533,18 @@ int tb_path_activate(struct tb_path *path) __tb_path_deactivate_hop(path->hops[i].in_port, path->hops[i].in_hop_index, path->clear_fc); - /* dword 0 */ + /* Needed for USB4 routers, read path config space before write */ + res = tb_port_read(path->hops[i].in_port, &hop, TB_CFG_HOPS, + 2 * path->hops[i].in_hop_index, 2); + if (res) + goto err; + hop.next_hop = path->hops[i].next_hop_index; hop.out_port = path->hops[i].out_port->port; - hop.initial_credits = path->hops[i].initial_credits; hop.pmps = path->hops[i].pm_support; hop.unknown1 = 0; hop.enable = 1; - /* dword 1 */ out_mask = (i == path->path_length - 1) ? TB_PATH_DESTINATION : TB_PATH_INTERNAL; in_mask = (i == 0) ? TB_PATH_SOURCE : TB_PATH_INTERNAL; @@ -550,12 +554,21 @@ int tb_path_activate(struct tb_path *path) hop.drop_packages = path->drop_packages; hop.counter = path->hops[i].in_counter_index; hop.counter_enable = path->hops[i].in_counter_index != -1; - hop.ingress_fc = path->ingress_fc_enable & in_mask; hop.egress_fc = path->egress_fc_enable & out_mask; - hop.ingress_shared_buffer = path->ingress_shared_buffer - & in_mask; - hop.egress_shared_buffer = path->egress_shared_buffer - & out_mask; + hop.egress_shared_buffer = path->egress_shared_buffer & out_mask; + /* + * Protocol adapters IFC and ISE bits, and Path Credits + * Allocated are vendor defined in the USB4 spec so we + * program them only for pre-USB4 and lane adapters. + */ + if (tb_port_is_null(path->hops[i].in_port) || + !tb_switch_is_usb4(path->hops[i].in_port->sw)) { + hop.initial_credits = path->hops[i].initial_credits; + hop.ingress_fc = path->ingress_fc_enable & in_mask; + hop.ingress_shared_buffer = + path->ingress_shared_buffer & in_mask; + } + hop.unknown3 = 0; tb_port_dbg(path->hops[i].in_port, "Writing hop %d\n", i); -- 2.47.3