[PATCH 14/19] thunderbolt: Add QUIRK_NO_USB3_BW_ALLOC
Sven Peter
sven at kernel.org
Sun Aug 30 13:19:32 PDT 2026
The host routers on Apple Silicon do not implement USB3 bandwidth
allocation registers: the CMR bit set in ADP_USB3_CS_2 by
usb4_usb3_port_cm_request() is never acknowledged and every USB3 tunnel
bringup fails there after the timeout:
[ 49.259325] thunderbolt-apple-nhi 501f00000.nhi: 1:16: available bandwidth for new USB3 tunnel 18000/18000 Mb/s
[ 49.265869] thunderbolt-apple-nhi 501f00000.nhi: 1:16: maximum required bandwidth for USB3 tunnel 9000 Mb/s
[ 49.267894] thunderbolt-apple-nhi 501f00000.nhi: 0:4 <-> 1:16 (USB3): activating
[ 49.269410] thunderbolt-apple-nhi 501f00000.nhi: 0:4 <-> 1:16 (USB3): allocating initial bandwidth 9000/9000 Mb/s
[ 50.771764] thunderbolt-apple-nhi 501f00000.nhi: 1:16: USB3 tunnel activation failed, aborting
Add a quirk to skip bandwidth allocation entirely but keep tracking
the initial allocation in software for the consumed bandwidth
calculation. For completeness, discovered tunnels book 90% of the
maximum link rate in software, matching tb_tunnel_alloc_usb3(), although
Apple Silicon cannot have any pre-existing tunnels.
Signed-off-by: Sven Peter <sven at kernel.org>
---
drivers/thunderbolt/nhi.h | 1 +
drivers/thunderbolt/tb.c | 8 ++++++
drivers/thunderbolt/tb.h | 3 +++
drivers/thunderbolt/tunnel.c | 59 +++++++++++++++++++++++++++++---------------
4 files changed, 51 insertions(+), 20 deletions(-)
diff --git a/drivers/thunderbolt/nhi.h b/drivers/thunderbolt/nhi.h
index c2d16ab6994e..afd9a11489a9 100644
--- a/drivers/thunderbolt/nhi.h
+++ b/drivers/thunderbolt/nhi.h
@@ -169,6 +169,7 @@ struct tb_nhi_ops {
#define QUIRK_E2E BIT(1)
#define QUIRK_RESET_DMA_ON_TEARDOWN BIT(2)
#define QUIRK_NO_DMA_PORT BIT(3)
+#define QUIRK_NO_USB3_BW_ALLOC BIT(4)
/*
* Minimal number of vectors when we use MSI-X. Two for control channel
diff --git a/drivers/thunderbolt/tb.c b/drivers/thunderbolt/tb.c
index c43cdd2c2e2e..7ab53a30fe30 100644
--- a/drivers/thunderbolt/tb.c
+++ b/drivers/thunderbolt/tb.c
@@ -3044,6 +3044,14 @@ static int tb_start(struct tb *tb, bool reset)
*/
tb->root_switch->no_dma_port = tb->nhi->quirks & QUIRK_NO_DMA_PORT;
+ /*
+ * Apple Silicon host routers do not implement the USB3 bandwidth
+ * allocation registers: the CMR/HCA handshake is never acked and
+ * times out. Bandwidth for USB3 tunnels is only booked in software
+ * on these machines.
+ */
+ tb->root_switch->no_usb3_bw_alloc = tb->nhi->quirks & QUIRK_NO_USB3_BW_ALLOC;
+
ret = tb_switch_configure(tb->root_switch);
if (ret) {
tb_switch_put(tb->root_switch);
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index 0977cd690d7e..530b0e6c3a11 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -140,6 +140,8 @@ struct tb_switch_tmu {
* @nvm: Pointer to the NVM if the switch has one (%NULL otherwise)
* @no_nvm_upgrade: Prevent NVM upgrade of this switch
* @no_dma_port: Prevent adding the DMA port of this switch
+ * @no_usb3_bw_alloc: Host router does not implement the USB3 bandwidth
+ * allocation registers (ADP_USB3_CS_1..4)
* @safe_mode: The switch is in safe-mode
* @boot: Whether the switch was already authorized on boot or not
* @rpm: The switch supports runtime PM
@@ -196,6 +198,7 @@ struct tb_switch {
struct tb_nvm *nvm;
bool no_nvm_upgrade;
bool no_dma_port;
+ bool no_usb3_bw_alloc;
bool safe_mode;
bool boot;
bool rpm;
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 7e8284575dff..9178120a6b66 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -2268,24 +2268,40 @@ struct tb_tunnel *tb_tunnel_discover_usb3(struct tb *tb, struct tb_port *down,
if (!tb_route(down->sw)) {
int ret;
- /*
- * Read the initial bandwidth allocation for the first
- * hop tunnel.
- */
- ret = usb4_usb3_port_allocated_bandwidth(down,
- &tunnel->allocated_up, &tunnel->allocated_down);
- if (ret)
- goto err_deactivate;
+ tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
+
+ if (down->sw->no_usb3_bw_alloc) {
+ /*
+ * The host router does not implement the bandwidth
+ * allocation registers and nothing can be read back
+ * here. Book 90% of the maximum link rate in software
+ * instead.
+ */
+ ret = tb_usb3_max_link_rate(tunnel->dst_port, down);
+ if (ret < 0)
+ goto err_deactivate;
+
+ tunnel->allocated_up = ret * 90 / 100;
+ tunnel->allocated_down = tunnel->allocated_up;
+ } else {
+ /*
+ * Read the initial bandwidth allocation for the first
+ * hop tunnel.
+ */
+ ret = usb4_usb3_port_allocated_bandwidth(down,
+ &tunnel->allocated_up, &tunnel->allocated_down);
+ if (ret)
+ goto err_deactivate;
+
+ tunnel->pre_activate = tb_usb3_pre_activate;
+ tunnel->release_unused_bandwidth =
+ tb_usb3_release_unused_bandwidth;
+ tunnel->reclaim_available_bandwidth =
+ tb_usb3_reclaim_available_bandwidth;
+ }
tb_tunnel_dbg(tunnel, "currently allocated bandwidth %d/%d Mb/s\n",
tunnel->allocated_up, tunnel->allocated_down);
-
- tunnel->pre_activate = tb_usb3_pre_activate;
- tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
- tunnel->release_unused_bandwidth =
- tb_usb3_release_unused_bandwidth;
- tunnel->reclaim_available_bandwidth =
- tb_usb3_reclaim_available_bandwidth;
}
tb_tunnel_dbg(tunnel, "discovered\n");
@@ -2365,12 +2381,15 @@ struct tb_tunnel *tb_tunnel_alloc_usb3(struct tb *tb, struct tb_port *up,
tunnel->allocated_up = min(max_rate, max_up);
tunnel->allocated_down = min(max_rate, max_down);
- tunnel->pre_activate = tb_usb3_pre_activate;
tunnel->consumed_bandwidth = tb_usb3_consumed_bandwidth;
- tunnel->release_unused_bandwidth =
- tb_usb3_release_unused_bandwidth;
- tunnel->reclaim_available_bandwidth =
- tb_usb3_reclaim_available_bandwidth;
+
+ if (!down->sw->no_usb3_bw_alloc) {
+ tunnel->pre_activate = tb_usb3_pre_activate;
+ tunnel->release_unused_bandwidth =
+ tb_usb3_release_unused_bandwidth;
+ tunnel->reclaim_available_bandwidth =
+ tb_usb3_reclaim_available_bandwidth;
+ }
}
return tunnel;
--
2.55.0
More information about the linux-arm-kernel
mailing list