linux-kernel - [PATCH v2] usb: dwc3: Always deassert xilinx resets

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives
Hash Suite: Windows password security audit tool. GUI, reports in PDF.
[<prev] [next>] [day] [month] [year] [list]
Message-Id: <20260115145153.3332570-1-sean.anderson@linux.dev>
Date: Thu, 15 Jan 2026 09:51:53 -0500
From: Sean Anderson <sean.anderson@...ux.dev>
To: Thinh Nguyen <Thinh.Nguyen@...opsys.com>,
	linux-usb@...r.kernel.org
Cc: Radhey Shyam Pandey <radhey.shyam.pandey@....com>,
	Neal Frager <neal.frager@....com>,
	Philipp Zabel <p.zabel@...gutronix.de>,
	Michal Simek <michal.simek@....com>,
	linux-kernel@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Sean Anderson <sean.anderson@...ux.dev>
Subject: [PATCH v2] usb: dwc3: Always deassert xilinx resets

I am working on moving serdes initialization to the phy (and consumer)
drivers to improve flexibility and boot times (depending on configuration).
Currently, core resets are released in the bootloader by init_serdes() in
psu_init_gpl.c. In order to remove init_serdes, we need to handle the case
where the bootloader never released the core resets. If we don't have a
usb3 phy we don't need to assert the core resets, but deassert them anyway
to handle this case.

We could assert all resets every boot, but I believe the existing procedure
is an optimization to reduce boot time when the bootloader has already
initialized USB. So this patch preserves the separate code paths.

Signed-off-by: Sean Anderson <sean.anderson@...ux.dev>
Acked-by: Thinh Nguyen <Thinh.Nguyen@...opsys.com>
---

Changes in v2:
- Update commit message

 drivers/usb/dwc3/dwc3-xilinx.c | 67 ++++++++++++++++------------------
 1 file changed, 32 insertions(+), 35 deletions(-)

diff --git a/drivers/usb/dwc3/dwc3-xilinx.c b/drivers/usb/dwc3/dwc3-xilinx.c
index 0a8c47876ff9..f41b0da5e89d 100644
--- a/drivers/usb/dwc3/dwc3-xilinx.c
+++ b/drivers/usb/dwc3/dwc3-xilinx.c
@@ -132,21 +132,6 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
 		goto err;
 	}
 
-	/*
-	 * The following core resets are not required unless a USB3 PHY
-	 * is used, and the subsequent register settings are not required
-	 * unless a core reset is performed (they should be set properly
-	 * by the first-stage boot loader, but may be reverted by a core
-	 * reset). They may also break the configuration if USB3 is actually
-	 * in use but the usb3-phy entry is missing from the device tree.
-	 * Therefore, skip these operations in this case.
-	 */
-	if (!priv_data->usb3_phy) {
-		/* Deselect the PIPE Clock Select bit in FPD PIPE Clock register */
-		writel(PIPE_CLK_DESELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
-		goto skip_usb3_phy;
-	}
-
 	crst = devm_reset_control_get_exclusive(dev, "usb_crst");
 	if (IS_ERR(crst)) {
 		ret = PTR_ERR(crst);
@@ -171,22 +156,31 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
 		goto err;
 	}
 
-	ret = reset_control_assert(crst);
-	if (ret < 0) {
-		dev_err(dev, "Failed to assert core reset\n");
-		goto err;
-	}
+	/*
+	 * Asserting the core resets is not required unless a USB3 PHY is used.
+	 * They may also break the configuration if USB3 is actually in use but
+	 * the usb3-phy entry is missing from the device tree. Therefore, skip
+	 * a full reset cycle and just deassert the resets if the phy is
+	 * absent.
+	 */
+	if (priv_data->usb3_phy) {
+		ret = reset_control_assert(crst);
+		if (ret < 0) {
+			dev_err(dev, "Failed to assert core reset\n");
+			goto err;
+		}
 
-	ret = reset_control_assert(hibrst);
-	if (ret < 0) {
-		dev_err(dev, "Failed to assert hibernation reset\n");
-		goto err;
-	}
+		ret = reset_control_assert(hibrst);
+		if (ret < 0) {
+			dev_err(dev, "Failed to assert hibernation reset\n");
+			goto err;
+		}
 
-	ret = reset_control_assert(apbrst);
-	if (ret < 0) {
-		dev_err(dev, "Failed to assert APB reset\n");
-		goto err;
+		ret = reset_control_assert(apbrst);
+		if (ret < 0) {
+			dev_err(dev, "Failed to assert APB reset\n");
+			goto err;
+		}
 	}
 
 	ret = phy_init(priv_data->usb3_phy);
@@ -201,11 +195,15 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
 		goto err;
 	}
 
-	/* Set PIPE Power Present signal in FPD Power Present Register*/
-	writel(FPD_POWER_PRSNT_OPTION, priv_data->regs + XLNX_USB_FPD_POWER_PRSNT);
-
-	/* Set the PIPE Clock Select bit in FPD PIPE Clock register */
-	writel(PIPE_CLK_SELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
+	if (priv_data->usb3_phy) {
+		/* Set PIPE Power Present signal in FPD Power Present Register*/
+		writel(FPD_POWER_PRSNT_OPTION, priv_data->regs + XLNX_USB_FPD_POWER_PRSNT);
+		/* Set the PIPE Clock Select bit in FPD PIPE Clock register */
+		writel(PIPE_CLK_SELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
+	} else {
+		/* Deselect the PIPE Clock Select bit in FPD PIPE Clock register */
+		writel(PIPE_CLK_DESELECT, priv_data->regs + XLNX_USB_FPD_PIPE_CLK);
+	}
 
 	ret = reset_control_deassert(crst);
 	if (ret < 0) {
@@ -225,7 +223,6 @@ static int dwc3_xlnx_init_zynqmp(struct dwc3_xlnx *priv_data)
 		goto err;
 	}
 
-skip_usb3_phy:
 	/* ulpi reset via gpio-modepin or gpio-framework driver */
 	reset_gpio = devm_gpiod_get_optional(dev, "reset", GPIOD_OUT_HIGH);
 	if (IS_ERR(reset_gpio)) {
-- 
2.35.1.1320.gc452695387.dirty