[PATCH v2 1/4] usb: early: Avoid using DbC if already enabled

[Connor Davis <connojdavis@xxxxxxxxx>]

Check if the debug capability is enabled in early_xdbc_parse_parameter,
and if it is, return with an error. This avoids collisions with whatever
enabled the DbC prior to linux starting.

Signed-off-by: Connor Davis <connojdavis@xxxxxxxxx>
---
 drivers/usb/early/xhci-dbc.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/drivers/usb/early/xhci-dbc.c b/drivers/usb/early/xhci-dbc.c
index be4ecbabdd58..ca67fddc2d36 100644
--- a/drivers/usb/early/xhci-dbc.c
+++ b/drivers/usb/early/xhci-dbc.c
@@ -642,6 +642,16 @@ int __init early_xdbc_parse_parameter(char *s)
        }
        xdbc.xdbc_reg = (struct xdbc_regs __iomem *)(xdbc.xhci_base + offset);
 
+       if (readl(&xdbc.xdbc_reg->control) & CTRL_DBC_ENABLE) {
+               pr_notice("xhci debug capability already in use\n");
+               early_iounmap(xdbc.xhci_base, xdbc.xhci_length);
+               xdbc.xdbc_reg = NULL;
+               xdbc.xhci_base = NULL;
+               xdbc.xhci_length = 0;
+
+               return -ENODEV;
+       }
+
        return 0;
 }
 
-- 
2.31.1