usb: typec: ucsi: Handle incorrect num_connectors capability

The UCSI spec states that the num_connectors field is 7 bits, and the
8th bit is reserved and should be set to zero.
Some buggy FW has been known to set this bit, and it can lead to a
system not booting.
Flag that the FW is not behaving correctly, and auto-fix the value
so that the system boots correctly.

Found on Lenovo P1 G8 during Linux enablement program. The FW will
be fixed, but seemed worth addressing in case it hit platforms that
aren't officially Linux supported.

Signed-off-by: Mark Pearson <mpearson-lenovo@squebb.ca>
Reviewed-by: Heikki Krogerus <heikki.krogerus@linux.intel.com>
Link: https://lore.kernel.org/r/20250821185319.2585023-1-mpearson-lenovo@squebb.ca
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/usb/typec/ucsi/ucsi.c b/drivers/usb/typec/ucsi/ucsi.c
index 3f568f790f39b0271667e80816270274b8dd3008..3995483a0aa097b822046e819f994164d6183b0d 100644 (file)
--- a/drivers/usb/typec/ucsi/ucsi.c
+++ b/drivers/usb/typec/ucsi/ucsi.c
@@ -1807,6 +1807,12 @@ static int ucsi_init(struct ucsi *ucsi)
                ret = -ENODEV;
                goto err_reset;
        }
+       /* Check if reserved bit set. This is out of spec but happens in buggy FW */
+       if (ucsi->cap.num_connectors & 0x80) {
+               dev_warn(ucsi->dev, "UCSI: Invalid num_connectors %d. Likely buggy FW\n",
+                        ucsi->cap.num_connectors);
+               ucsi->cap.num_connectors &= 0x7f; // clear bit and carry on
+       }
 
        /* Allocate the connectors. Released in ucsi_unregister() */
        connector = kcalloc(ucsi->cap.num_connectors + 1, sizeof(*connector), GFP_KERNEL);