[PATCH -next v3] thunderbolt: Add quirk to reset host interface on DMA path teardown for AMD USB4 routers

[PATCH -next v3] thunderbolt: Add quirk to reset host interface on DMA path teardown for AMD USB4 routers

[Basavaraj Natikar]

Some AMD USB4 host routers have a bug in the Host Interface where
DMA path setup and teardown cycles may cause the Tx ring to hang.

Fix this by issuing a Host Interface Reset on every DMA path teardown
for affected routers. The Host Interface Reset brings the registers in
the memory BAR to their default state and clears the End-to-End Flow
Control state, preventing the hang condition.

Co-developed-by: Sanath S <Sanath.S@amd.com>
Signed-off-by: Sanath S <Sanath.S@amd.com>
Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
---
v3:
- nhi_reset_interface() takes struct tb_nhi.
- Rename the quirk to QUIRK_RESET_DMA_ON_TEARDOWN.
- Give the AMD NHI PCI device IDs symbolic names in nhi.h.
- Reset the host interface through nhi->ops->reset_interface.

v2: https://lore.kernel.org/all/20260805111811.517996-1-Basavaraj.Natikar@amd.com/
v1: https://lore.kernel.org/all/20260804122638.1623429-1-Basavaraj.Natikar@amd.com/

 drivers/thunderbolt/domain.c   | 28 +++++++++++++++++++++++++++-
 drivers/thunderbolt/nhi.c      | 26 ++++++++++++++++++++++++++
 drivers/thunderbolt/nhi.h      | 16 ++++++++++++++++
 drivers/thunderbolt/nhi_regs.h |  4 ++++
 drivers/thunderbolt/pci.c      | 23 +++++++++++++++++++++++
 5 files changed, 96 insertions(+), 1 deletion(-)

diff --git a/drivers/thunderbolt/domain.c b/drivers/thunderbolt/domain.c
index 24611f05b3cd..62896930c93e 100644
--- a/drivers/thunderbolt/domain.c
+++ b/drivers/thunderbolt/domain.c
@@ -788,6 +788,23 @@ int tb_domain_approve_xdomain_paths(struct tb *tb, struct tb_xdomain *xd,
 			transmit_ring, receive_path, receive_ring);
 }
 
+static void tb_domain_reset_interface(struct tb *tb)
+{
+	struct tb_nhi *nhi = tb->nhi;
+
+	if (!nhi->ops->reset_interface)
+		return;
+
+	mutex_lock(&tb->lock);
+
+	/* The reset clears the ring state so stop the control channel */
+	tb_ctl_stop(tb->ctl);
+	nhi->ops->reset_interface(nhi);
+	tb_ctl_start(tb->ctl);
+
+	mutex_unlock(&tb->lock);
+}
+
 /**
  * tb_domain_disconnect_xdomain_paths() - Disable DMA paths for XDomain
  * @tb: Domain disabling the DMA paths
@@ -810,11 +827,20 @@ int tb_domain_disconnect_xdomain_paths(struct tb *tb, struct tb_xdomain *xd,
 				       int transmit_path, int transmit_ring,
 				       int receive_path, int receive_ring)
 {
+	int ret;
+
 	if (!tb->cm_ops->disconnect_xdomain_paths)
 		return -ENOTSUPP;
 
-	return tb->cm_ops->disconnect_xdomain_paths(tb, xd, transmit_path,
+	ret = tb->cm_ops->disconnect_xdomain_paths(tb, xd, transmit_path,
 			transmit_ring, receive_path, receive_ring);
+	if (ret)
+		return ret;
+
+	if (tb->nhi->quirks & QUIRK_RESET_DMA_ON_TEARDOWN)
+		tb_domain_reset_interface(tb);
+
+	return 0;
 }
 
 static int disconnect_xdomain(struct device *dev, void *data)
diff --git a/drivers/thunderbolt/nhi.c b/drivers/thunderbolt/nhi.c
index 383a36212f70..76fb14221438 100644
--- a/drivers/thunderbolt/nhi.c
+++ b/drivers/thunderbolt/nhi.c
@@ -1160,6 +1160,32 @@ static void nhi_reset(struct tb_nhi *nhi)
 	dev_warn(nhi->dev, "timeout resetting host router\n");
 }
 
+/**
+ * nhi_reset_interface() - Reset the host interface
+ * @nhi: Host interface to reset
+ *
+ * Brings the registers in the memory BAR back to their default state and
+ * clears the End-to-End Flow Control state. The caller is responsible for
+ * stopping the control channel over the reset because it clears the ring
+ * state as well.
+ */
+void nhi_reset_interface(struct tb_nhi *nhi)
+{
+	u32 val;
+
+	val = ioread32(nhi->iobase + REG_CAPS);
+	/* Only v1 host interfaces implement the reset */
+	if (FIELD_GET(REG_CAPS_VERSION_MASK, val) >= REG_CAPS_VERSION_2)
+		return;
+
+	dev_dbg(nhi->dev, "issuing host interface reset\n");
+
+	iowrite32(REG_HOST_INTERFACE_RESET_RST,
+		  nhi->iobase + REG_HOST_INTERFACE_RESET);
+	/* Wait for tHIReset (10 ms) to complete */
+	usleep_range(10000, 20000);
+}
+
 static struct tb *nhi_select_cm(struct tb_nhi *nhi)
 {
 	struct tb *tb;
diff --git a/drivers/thunderbolt/nhi.h b/drivers/thunderbolt/nhi.h
index d488eadadfce..15bff76c66bc 100644
--- a/drivers/thunderbolt/nhi.h
+++ b/drivers/thunderbolt/nhi.h
@@ -36,6 +36,7 @@ irqreturn_t nhi_msi(int irq, void *data);
 irqreturn_t ring_msix(int irq, void *data);
 int nhi_probe(struct tb_nhi *nhi);
 void nhi_shutdown(struct tb_nhi *nhi);
+void nhi_reset_interface(struct tb_nhi *nhi);
 extern const struct dev_pm_ops nhi_pm_ops;
 
 /**
@@ -52,6 +53,7 @@ extern const struct dev_pm_ops nhi_pm_ops;
  * @release_ring_irq: NHI specific interrupt release hook
  * @is_present: Whether the device is currently present on the parent bus
  * @init_interrupts: NHI specific interrupt initialization hook
+ * @reset_interface: Resets the host interface
  */
 struct tb_nhi_ops {
 	int (*init)(struct tb_nhi *nhi);
@@ -66,6 +68,7 @@ struct tb_nhi_ops {
 	void (*release_ring_irq)(struct tb_ring *ring);
 	bool (*is_present)(struct tb_nhi *nhi);
 	int (*init_interrupts)(struct tb_nhi *nhi);
+	void (*reset_interface)(struct tb_nhi *nhi);
 };
 
 /*
@@ -116,11 +119,24 @@ struct tb_nhi_ops {
 #define PCI_DEVICE_ID_INTEL_PTL_P_NHI0			0xe433
 #define PCI_DEVICE_ID_INTEL_PTL_P_NHI1			0xe434
 
+#define PCI_DEVICE_ID_AMD_1AH_M60H_NHI0			0x1120
+#define PCI_DEVICE_ID_AMD_1AH_M60H_NHI1			0x1121
+#define PCI_DEVICE_ID_AMD_1AH_M68H_NHI0			0x113b
+#define PCI_DEVICE_ID_AMD_1AH_M68H_NHI1			0x113c
+#define PCI_DEVICE_ID_AMD_1AH_M80H_NHI0			0x1155
+#define PCI_DEVICE_ID_AMD_1AH_M80H_NHI1			0x1158
+#define PCI_DEVICE_ID_AMD_1AH_M80H_NHI2			0x1159
+#define PCI_DEVICE_ID_AMD_1AH_M24H_NHI0			0x151c
+#define PCI_DEVICE_ID_AMD_1AH_M24H_NHI1			0x151d
+#define PCI_DEVICE_ID_AMD_1AH_M70H_NHI0			0x158d
+#define PCI_DEVICE_ID_AMD_1AH_M70H_NHI1			0x158e
+
 #define PCI_CLASS_SERIAL_USB_USB4			0x0c0340
 
 /* Host interface quirks */
 #define QUIRK_AUTO_CLEAR_INT	BIT(0)
 #define QUIRK_E2E		BIT(1)
+#define QUIRK_RESET_DMA_ON_TEARDOWN	BIT(2)
 
 /*
  * Minimal number of vectors when we use MSI-X. Two for control channel
diff --git a/drivers/thunderbolt/nhi_regs.h b/drivers/thunderbolt/nhi_regs.h
index d6a197fabc74..99df60b6db36 100644
--- a/drivers/thunderbolt/nhi_regs.h
+++ b/drivers/thunderbolt/nhi_regs.h
@@ -115,6 +115,10 @@ struct ring_desc {
 #define REG_CAPS_VERSION_MASK		GENMASK(23, 16)
 #define REG_CAPS_VERSION_2		0x40
 
+/* Host Interface Reset - resets TX/RX rings and E2E flow control counters */
+#define REG_HOST_INTERFACE_RESET	0x39858
+#define REG_HOST_INTERFACE_RESET_RST	BIT(0)
+
 #define REG_DMA_MISC			0x39864
 #define REG_DMA_MISC_INT_AUTO_CLEAR     BIT(2)
 #define REG_DMA_MISC_DISABLE_AUTO_CLEAR	BIT(17)
diff --git a/drivers/thunderbolt/pci.c b/drivers/thunderbolt/pci.c
index 8462ccb59b7e..99333729f3c2 100644
--- a/drivers/thunderbolt/pci.c
+++ b/drivers/thunderbolt/pci.c
@@ -62,6 +62,27 @@ static void nhi_pci_check_quirks(struct tb_nhi_pci *nhi_pci)
 			nhi->quirks |= QUIRK_E2E;
 			break;
 		}
+	} else if (pdev->vendor == PCI_VENDOR_ID_AMD) {
+		switch (pdev->device) {
+		case PCI_DEVICE_ID_AMD_1AH_M60H_NHI0:
+		case PCI_DEVICE_ID_AMD_1AH_M60H_NHI1:
+		case PCI_DEVICE_ID_AMD_1AH_M68H_NHI0:
+		case PCI_DEVICE_ID_AMD_1AH_M68H_NHI1:
+		case PCI_DEVICE_ID_AMD_1AH_M80H_NHI0:
+		case PCI_DEVICE_ID_AMD_1AH_M80H_NHI1:
+		case PCI_DEVICE_ID_AMD_1AH_M80H_NHI2:
+		case PCI_DEVICE_ID_AMD_1AH_M24H_NHI0:
+		case PCI_DEVICE_ID_AMD_1AH_M24H_NHI1:
+		case PCI_DEVICE_ID_AMD_1AH_M70H_NHI0:
+		case PCI_DEVICE_ID_AMD_1AH_M70H_NHI1:
+			/*
+			 * These AMD hosts may hang the Tx ring when the
+			 * DMA paths are torn down so they need the host
+			 * interface reset after each teardown.
+			 */
+			nhi->quirks |= QUIRK_RESET_DMA_ON_TEARDOWN;
+			break;
+		}
 	}
 }
 
@@ -258,6 +279,7 @@ static const struct tb_nhi_ops pci_nhi_default_ops = {
 	.shutdown = nhi_pci_release_irq,
 	.is_present = nhi_pci_is_present,
 	.init_interrupts = nhi_pci_init_msi,
+	.reset_interface = nhi_reset_interface,
 };
 
 /* Ice Lake specific NHI operations */
@@ -441,6 +463,7 @@ static const struct tb_nhi_ops icl_nhi_ops = {
 	.release_ring_irq = nhi_pci_ring_release_msix,
 	.is_present = nhi_pci_is_present,
 	.init_interrupts = nhi_pci_init_msi,
+	.reset_interface = nhi_reset_interface,
 };
 
 static int nhi_pci_probe(struct pci_dev *pdev, const struct pci_device_id *id)
-- 
2.34.1

Re: [PATCH -next v3] thunderbolt: Add quirk to reset host interface on DMA path teardown for AMD USB4 routers

[Mika Westerberg]

Hi,

On Thu, Aug 06, 2026 at 06:29:29PM +0530, Basavaraj Natikar wrote:
> Some AMD USB4 host routers have a bug in the Host Interface where
> DMA path setup and teardown cycles may cause the Tx ring to hang.
> 
> Fix this by issuing a Host Interface Reset on every DMA path teardown
> for affected routers. The Host Interface Reset brings the registers in
> the memory BAR to their default state and clears the End-to-End Flow
> Control state, preventing the hang condition.
> 
> Co-developed-by: Sanath S <Sanath.S@amd.com>
> Signed-off-by: Sanath S <Sanath.S@amd.com>
> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>

I did few minor cosmetic tweaks and applied to thunderbolt.git/next,
thanks!

Re: [PATCH -next v3] thunderbolt: Add quirk to reset host interface on DMA path teardown for AMD USB4 routers

[Basavaraj Natikar]

On 8/7/2026 11:46 AM, Mika Westerberg wrote:
> Hi,
>
> On Thu, Aug 06, 2026 at 06:29:29PM +0530, Basavaraj Natikar wrote:
>> Some AMD USB4 host routers have a bug in the Host Interface where
>> DMA path setup and teardown cycles may cause the Tx ring to hang.
>>
>> Fix this by issuing a Host Interface Reset on every DMA path teardown
>> for affected routers. The Host Interface Reset brings the registers in
>> the memory BAR to their default state and clears the End-to-End Flow
>> Control state, preventing the hang condition.
>>
>> Co-developed-by: Sanath S <Sanath.S@amd.com>
>> Signed-off-by: Sanath S <Sanath.S@amd.com>
>> Signed-off-by: Basavaraj Natikar <Basavaraj.Natikar@amd.com>
> I did few minor cosmetic tweaks and applied to thunderbolt.git/next,

Thanks a lot Mika, appreciate the review and the tweaks!

Thanks,
--
Basavaraj