[PATCH v2 17/22] thunderbolt: Add QUIRK_NO_USB3_BW_ALLOC

[Sven Peter]

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/quirks.c |  9 +++++++
 drivers/thunderbolt/tb.h     |  2 ++
 drivers/thunderbolt/tunnel.c | 60 +++++++++++++++++++++++++++++---------------
 3 files changed, 51 insertions(+), 20 deletions(-)

diff --git a/drivers/thunderbolt/quirks.c b/drivers/thunderbolt/quirks.c
index 9f7914ac2f48..2ac1bfa01c15 100644
--- a/drivers/thunderbolt/quirks.c
+++ b/drivers/thunderbolt/quirks.c
@@ -46,6 +46,12 @@ static void quirk_usb3_maximum_bandwidth(struct tb_switch *sw)
 	}
 }
 
+static void quirk_no_usb3_bw_alloc(struct tb_switch *sw)
+{
+	sw->quirks |= QUIRK_NO_USB3_BW_ALLOC;
+	tb_sw_dbg(sw, "disabling USB3 bandwidth allocation\n");
+}
+
 static void quirk_block_rpm_in_redrive(struct tb_switch *sw)
 {
 	sw->quirks |= QUIRK_KEEP_POWER_IN_DP_REDRIVE;
@@ -61,6 +67,9 @@ struct tb_quirk {
 };
 
 static const struct tb_quirk tb_quirks[] = {
+	/* Apple Silicon host routers do not support USB3 bandwidth allocation */
+	{ 0x05ac, 0x2000, 0x0000, 0x0000, quirk_no_usb3_bw_alloc },
+
 	/* Dell WD19TB supports self-authentication on unplug */
 	{ 0x0000, 0x0000, 0x00d4, 0xb070, quirk_force_power_link },
 	{ 0x0000, 0x0000, 0x00d4, 0xb071, quirk_force_power_link },
diff --git a/drivers/thunderbolt/tb.h b/drivers/thunderbolt/tb.h
index fbd1a0a9927a..7c2fcf20e49f 100644
--- a/drivers/thunderbolt/tb.h
+++ b/drivers/thunderbolt/tb.h
@@ -26,6 +26,8 @@
 #define QUIRK_NO_CLX					BIT(1)
 /* Need to keep power on while USB4 port is in redrive mode */
 #define QUIRK_KEEP_POWER_IN_DP_REDRIVE			BIT(2)
+/* Does not support USB3 bandwidth allocation */
+#define QUIRK_NO_USB3_BW_ALLOC				BIT(3)
 
 /**
  * struct tb_nvm - Structure holding NVM information
diff --git a/drivers/thunderbolt/tunnel.c b/drivers/thunderbolt/tunnel.c
index 7e8284575dff..0893ec19d606 100644
--- a/drivers/thunderbolt/tunnel.c
+++ b/drivers/thunderbolt/tunnel.c
@@ -2268,24 +2268,41 @@ 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->quirks & QUIRK_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 +2382,15 @@ 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->quirks & QUIRK_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