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Message-Id: <20251204-diogo-tegra_phy-v1-3-51a2016d0be8@tecnico.ulisboa.pt>
Date: Thu, 04 Dec 2025 21:27:19 +0000
From: Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
To: Mathias Nyman <mathias.nyman@...el.com>,
Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
Thierry Reding <thierry.reding@...il.com>,
Jonathan Hunter <jonathanh@...dia.com>, JC Kuo <jckuo@...dia.com>,
Vinod Koul <vkoul@...nel.org>, Kishon Vijay Abraham I <kishon@...nel.org>,
Rob Herring <robh@...nel.org>, Krzysztof Kozlowski <krzk+dt@...nel.org>,
Conor Dooley <conor+dt@...nel.org>
Cc: linux-usb@...r.kernel.org, linux-tegra@...r.kernel.org,
linux-kernel@...r.kernel.org, linux-phy@...ts.infradead.org,
devicetree@...r.kernel.org, Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
Subject: [PATCH 3/5] phy: tegra: xusb: Fix ordering issue when switching
roles on USB2 ports
The current implementation of USB2 role switching on Tegra relies on
whichever the previous USB controller driver was using the PHY to first
"yield" it back to USB_ROLE_NONE before the next controller configures
it for the new role. However, no mechanism to guarantee this ordering
was implemented, and currently, in the general case, the configuration
functions tegra_xhci_id_work() and tegra_xudc_usb_role_sw_work() end up
running in the same order regardless of the transition being HOST->DEVICE
or DEVICE->HOST, leading to one of these transitions ending up in a
non-working state due to the new configuration being clobbered by the
previous controller driver setting USB_ROLE_NONE after the fact.
Fix this by introducing a helper that waits for the USB2 port’s current
role to become USB_ROLE_NONE and add it in the configuration functions
above before setting the role to either USB_ROLE_HOST or
USB_ROLE_DEVICE. The specific parameters of the helper function are
choices that seem reasonable in my testing and have no other basis.
This was tested on a Tegra210 platform (Smaug). However, due to the similar
approach in Tegra186 it is likely that not only this problem exists there
but that this patch also fixes it.
Signed-off-by: Diogo Ivo <diogo.ivo@...nico.ulisboa.pt>
---
drivers/phy/tegra/xusb.c | 23 +++++++++++++++++++++++
drivers/usb/gadget/udc/tegra-xudc.c | 4 ++++
drivers/usb/host/xhci-tegra.c | 15 ++++++++++-----
include/linux/phy/tegra/xusb.h | 1 +
4 files changed, 38 insertions(+), 5 deletions(-)
diff --git a/drivers/phy/tegra/xusb.c b/drivers/phy/tegra/xusb.c
index c89df95aa6ca..e05c3f2d1421 100644
--- a/drivers/phy/tegra/xusb.c
+++ b/drivers/phy/tegra/xusb.c
@@ -740,6 +740,29 @@ static void tegra_xusb_parse_usb_role_default_mode(struct tegra_xusb_port *port)
}
}
+bool tegra_xusb_usb2_port_wait_role_none(struct tegra_xusb_padctl *padctl, int index)
+{
+ struct tegra_xusb_usb2_port *usb2 = tegra_xusb_find_usb2_port(padctl,
+ index);
+ int retries = 5;
+
+ if (!usb2) {
+ dev_err(&usb2->base.dev, "no port found for USB2 lane %u\n", index);
+ return false;
+ }
+
+ do {
+ if (usb2->role == USB_ROLE_NONE)
+ return true;
+
+ usleep_range(50, 60);
+ } while (retries--);
+
+ dev_err(&usb2->base.dev, "timed out waiting for USB_ROLE_NONE");
+
+ return false;
+}
+
static int tegra_xusb_usb2_port_parse_dt(struct tegra_xusb_usb2_port *usb2)
{
struct tegra_xusb_port *port = &usb2->base;
diff --git a/drivers/usb/gadget/udc/tegra-xudc.c b/drivers/usb/gadget/udc/tegra-xudc.c
index 0c38fc37b6e6..72d725659e5f 100644
--- a/drivers/usb/gadget/udc/tegra-xudc.c
+++ b/drivers/usb/gadget/udc/tegra-xudc.c
@@ -698,8 +698,12 @@ static void tegra_xudc_restore_port_speed(struct tegra_xudc *xudc)
static void tegra_xudc_device_mode_on(struct tegra_xudc *xudc)
{
+ int port = tegra_xusb_padctl_get_port_number(xudc->curr_utmi_phy);
int err;
+ if (!tegra_xusb_usb2_port_wait_role_none(xudc->padctl, port))
+ return;
+
pm_runtime_get_sync(xudc->dev);
tegra_phy_xusb_utmi_pad_power_on(xudc->curr_utmi_phy);
diff --git a/drivers/usb/host/xhci-tegra.c b/drivers/usb/host/xhci-tegra.c
index 9c69fccdc6e8..9944593166a3 100644
--- a/drivers/usb/host/xhci-tegra.c
+++ b/drivers/usb/host/xhci-tegra.c
@@ -1352,18 +1352,23 @@ static void tegra_xhci_id_work(struct work_struct *work)
struct tegra_xusb_mbox_msg msg;
struct phy *phy = tegra_xusb_get_phy(tegra, "usb2",
tegra->otg_usb2_port);
+ enum usb_role role = USB_ROLE_NONE;
u32 status;
int ret;
dev_dbg(tegra->dev, "host mode %s\n", str_on_off(tegra->host_mode));
- mutex_lock(&tegra->lock);
- if (tegra->host_mode)
- phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_HOST);
- else
- phy_set_mode_ext(phy, PHY_MODE_USB_OTG, USB_ROLE_NONE);
+ if (tegra->host_mode) {
+ if (!tegra_xusb_usb2_port_wait_role_none(tegra->padctl,
+ tegra->otg_usb2_port))
+ return;
+ role = USB_ROLE_HOST;
+ }
+
+ mutex_lock(&tegra->lock);
+ phy_set_mode_ext(phy, PHY_MODE_USB_OTG, role);
mutex_unlock(&tegra->lock);
tegra->otg_usb3_port = tegra_xusb_padctl_get_usb3_companion(tegra->padctl,
diff --git a/include/linux/phy/tegra/xusb.h b/include/linux/phy/tegra/xusb.h
index 6ca51e0080ec..a0d3d5b7cf33 100644
--- a/include/linux/phy/tegra/xusb.h
+++ b/include/linux/phy/tegra/xusb.h
@@ -33,5 +33,6 @@ int tegra_xusb_padctl_disable_phy_sleepwalk(struct tegra_xusb_padctl *padctl, st
int tegra_xusb_padctl_enable_phy_wake(struct tegra_xusb_padctl *padctl, struct phy *phy);
int tegra_xusb_padctl_disable_phy_wake(struct tegra_xusb_padctl *padctl, struct phy *phy);
bool tegra_xusb_padctl_remote_wake_detected(struct tegra_xusb_padctl *padctl, struct phy *phy);
+bool tegra_xusb_usb2_port_wait_role_none(struct tegra_xusb_padctl *padctl, int index);
#endif /* PHY_TEGRA_XUSB_H */
--
2.52.0
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