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

From: Connor Davis <connojdavis@gmail.com>
To: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: Connor Davis <connojdavis@gmail.com>,
	Jann Horn <jannh@google.com>, Lee Jones <lee.jones@linaro.org>,
	Chunfeng Yun <chunfeng.yun@mediatek.com>,
	linux-usb@vger.kernel.org, linux-kernel@vger.kernel.org,
	xen-devel@lists.xenproject.org
Subject: [PATCH v2 1/4] usb: early: Avoid using DbC if already enabled
Date: Thu, 13 May 2021 18:56:48 -0600	[thread overview]
Message-ID: <d160cee9b61c0ec41c2cd5ff9b4e107011d39d8c.1620952511.git.connojdavis@gmail.com> (raw)
In-Reply-To: <cover.1620950220.git.connojdavis@gmail.com>

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@gmail.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


