[PATCH] usb: typec: ucsi: Do not report surplus partner altmodes as firmware bug

[PATCH] usb: typec: ucsi: Do not report surplus partner altmodes as firmware bug

[Paul Menzel]

On a Dell XPS 13 9370 (BIOS 1.21.0) with a Dell USB Type-C power adapter
connected, Linux 7.2.12 logs:

    ucsi_acpi USBC000:00: con2: Firmware bug: duplicate partner altmode SVID 0x413c at offset 1, ignoring but please contact the BIOS vendor to fix this issue.
    ucsi_acpi USBC000:00: con2: VDO mismatch: 0x00000001 vs 0x00000002

The port advertises one altmode for the Dell SVID, and the partner two
Modes, with VDOs 0x00000001 and 0x00000002. Only the first one is
registered:

    /sys/class/typec/port1/port1.2/svid:413c
    /sys/class/typec/port1/port1.2/vdo:0x00000001
    /sys/class/typec/port1-partner/port1-partner.0/svid:413c
    /sys/class/typec/port1-partner/port1-partner.0/vdo:0x00000001

A partner supporting more Modes of an SVID than the port is valid. As
the typec class pairs partner altmodes with port altmodes by SVID only,
skipping the surplus altmode is correct, but the warning blames the BIOS
for a configuration that is not a bug at all.

Report only exact SVID and VDO repeats as firmware bugs, and log a
surplus partner altmode with a different VDO at debug level. Which
altmodes are skipped does not change.

This also drops the "VDO mismatch" message, which can no longer trigger
and printed con->partner_altmode[partner_count - 1]->vdo. That indexes
all partner altmodes with a per-SVID count, so with altmodes of other
SVIDs registered first, it printed the VDO of an unrelated altmode.

Fixes: 67c92c6419ea ("usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware")
Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>
---

Notes:
    With this change, the Thunderbolt example from commit 67c92c6419ea
    (VDO 0x8087a043 vs 0x00000001) is only logged at debug level. If that
    case should stay visible, dev_info() is an alternative to dev_dbg().
    
    Tool use: Claude Code (claude-opus-5.5) traced the warning to commit
    67c92c6419ea, wrote the code change, and drafted the commit message from
    the dmesg and sysfs output of the affected system.

 drivers/usb/typec/ucsi/ucsi.c | 43 +++++++++++++++++------------------
 1 file changed, 21 insertions(+), 22 deletions(-)

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 5aab8ab9f0132..7edcf9c877ba0 100644
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -531,9 +531,7 @@ static int ucsi_register_altmode(struct ucsi_connector *con,
 }
 
 static void ucsi_dump_duplicate_altmode(struct ucsi_connector *con,
-					u8 recipient, u16 svid,
-					u32 existing_vdo, u32 new_vdo,
-					int offset)
+					u8 recipient, u16 svid, int offset)
 {
 	static const char * const recipient_names[] = {
 		[UCSI_RECIPIENT_CON]    = "port",
@@ -545,11 +543,6 @@ static void ucsi_dump_duplicate_altmode(struct ucsi_connector *con,
 	dev_warn(con->ucsi->dev,
 		 "con%d: Firmware bug: duplicate %s altmode SVID 0x%04x at offset %d, ignoring but please contact the BIOS vendor to fix this issue.\n",
 		 con->num, recipient_names[recipient], svid, offset);
-
-	if (existing_vdo != new_vdo)
-		dev_warn(con->ucsi->dev,
-			 "con%d: VDO mismatch: 0x%08x vs 0x%08x\n",
-			 con->num, existing_vdo, new_vdo);
 }
 
 /* Count altmodes in @altmodes that advertise @svid. */
@@ -590,8 +583,9 @@ static int ucsi_altmode_count_svid(struct typec_altmode **altmodes, u16 svid)
  *     SVID X as the authoritative cap and reject any partner altmode that
  *     would exceed it. This preserves legitimate multi-Mode partner
  *     altmodes (e.g. vendor SVIDs that the port really does advertise
- *     twice) while filtering the firmware-generated duplicates that have
- *     no port counterpart.
+ *     twice). Only an exact SVID+VDO repeat is reported as a firmware
+ *     bug: a partner may legitimately support more Modes of an SVID than
+ *     the port, so a surplus altmode with a different VDO is just skipped.
  */
 static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
 				      const struct ucsi_altmode *alt_batch, int batch_idx,
@@ -605,7 +599,7 @@ static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
 	for (k = 0; k < batch_idx; k++) {
 		if (alt_batch[k].svid == svid && alt_batch[k].mid == vdo) {
 			ucsi_dump_duplicate_altmode(con, recipient, svid,
-						    vdo, vdo, offset);
+						    offset);
 			return true;
 		}
 	}
@@ -620,13 +614,10 @@ static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
 		port_count = ucsi_altmode_count_svid(con->port_altmode, svid);
 		partner_count = ucsi_altmode_count_svid(con->partner_altmode,
 							svid);
-		if (port_count && partner_count >= port_count) {
-			ucsi_dump_duplicate_altmode(con, recipient, svid,
-						    con->partner_altmode[partner_count - 1]->vdo,
-						    vdo, offset);
-			return true;
-		}
-		return false;
+		if (!port_count || partner_count < port_count)
+			return false;
+		altmodes = con->partner_altmode;
+		break;
 	case UCSI_RECIPIENT_CON:
 		altmodes = con->port_altmode;
 		break;
@@ -637,7 +628,7 @@ static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
 		return false;
 	}
 
-	/* CON and SOP_P: drop only exact SVID+VDO duplicates. */
+	/* Report exact SVID+VDO duplicates as firmware bugs. */
 	for (k = 0; k < UCSI_MAX_ALTMODES; k++) {
 		if (!altmodes[k])
 			break;
@@ -645,12 +636,20 @@ static bool ucsi_altmode_is_duplicate(struct ucsi_connector *con, u8 recipient,
 		if (altmodes[k]->svid != svid || altmodes[k]->vdo != vdo)
 			continue;
 
-		ucsi_dump_duplicate_altmode(con, recipient, svid,
-					    altmodes[k]->vdo, vdo, offset);
+		ucsi_dump_duplicate_altmode(con, recipient, svid, offset);
 		return true;
 	}
 
-	return false;
+	/* CON and SOP_P: anything else is a distinct altmode. */
+	if (recipient != UCSI_RECIPIENT_SOP)
+		return false;
+
+	/* SOP: a further Mode of the SVID, but no port altmode to pair with. */
+	dev_dbg(con->ucsi->dev,
+		"con%d: partner altmode SVID 0x%04x VDO 0x%08x at offset %d exceeds the %d port altmode(s), ignoring\n",
+		con->num, svid, vdo, offset, port_count);
+
+	return true;
 }
 
 static int
-- 
2.54.0

Re: [PATCH] usb: typec: ucsi: Do not report surplus partner altmodes as firmware bug

[sashiko-bot]

> On a Dell XPS 13 9370 (BIOS 1.21.0) with a Dell USB Type-C power adapter
> connected, Linux 7.2.12 logs:
> 
>     ucsi_acpi USBC000:00: con2: Firmware bug: duplicate partner altmode SVID 0x413c at offset 1, ignoring but please contact the BIOS vendor to fix this issue.
>     ucsi_acpi USBC000:00: con2: VDO mismatch: 0x00000001 vs 0x00000002
> 
> The port advertises one altmode for the Dell SVID, and the partner two
> Modes, with VDOs 0x00000001 and 0x00000002. Only the first one is
> registered:
> 
>     /sys/class/typec/port1/port1.2/svid:413c
>     /sys/class/typec/port1/port1.2/vdo:0x00000001
>     /sys/class/typec/port1-partner/port1-partner.0/svid:413c
>     /sys/class/typec/port1-partner/port1-partner.0/vdo:0x00000001
> 
> [ ... ]
> all partner altmodes with a per-SVID count, so with altmodes of other
> SVIDs registered first, it printed the VDO of an unrelated altmode.
> 
> Fixes: 67c92c6419ea ("usb: typec: ucsi: Detect and skip duplicate altmodes from buggy firmware")
> Signed-off-by: Paul Menzel <pmenzel@molgen.mpg.de>

Sashiko has reviewed this patch and found no issues.

-- 
Sashiko AI review · https://sashiko.dev/#/patchset/20261103234750.27510-1-pmenzel@molgen.mpg.de?part=1