linux-kernel - [PATCH 1/3] usb: early: Avoid using DbC if already enabled

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Date:   Tue, 11 May 2021 18:18:19 -0600
From:   Connor Davis <connojdavis@...il.com>
To:     Greg Kroah-Hartman <gregkh@...uxfoundation.org>
Cc:     Connor Davis <connojdavis@...il.com>,
        Lee Jones <lee.jones@...aro.org>, Jann Horn <jannh@...gle.com>,
        Chunfeng Yun <chunfeng.yun@...iatek.com>,
        xen-devel@...ts.xenproject.org, linux-usb@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: [PATCH 1/3] usb: early: Avoid using DbC if already enabled

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@...il.com>
---
 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