[RFC PATCH v4 04/11] coco: guest: arm64: Support guest-initiated TDI lock/unlock transitions

["Aneesh Kumar K.V (Arm)" <aneesh.kumar@kernel.org>]

Add guest helpers to drive TDI state transitions through RHI:
- cca_device_lock() -> RHI_DA_TDI_CONFIG_LOCKED
- cca_device_unlock() -> RHI_DA_TDI_CONFIG_UNLOCKED

Use these helpers in the PCI TSM lock/unlock callbacks so a successful
lock path returns a live pci_tsm handle and unlock transitions the device
back to unlocked state.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
 drivers/virt/coco/arm-cca-guest/Makefile  |  2 +-
 drivers/virt/coco/arm-cca-guest/arm-cca.c |  9 ++++--
 drivers/virt/coco/arm-cca-guest/rsi-da.c  | 34 +++++++++++++++++++++++
 drivers/virt/coco/arm-cca-guest/rsi-da.h  |  3 ++
 4 files changed, 45 insertions(+), 3 deletions(-)
 create mode 100644 drivers/virt/coco/arm-cca-guest/rsi-da.c

diff --git a/drivers/virt/coco/arm-cca-guest/Makefile b/drivers/virt/coco/arm-cca-guest/Makefile
index 65c4cc52c154..11db7af095c9 100644
--- a/drivers/virt/coco/arm-cca-guest/Makefile
+++ b/drivers/virt/coco/arm-cca-guest/Makefile
@@ -2,4 +2,4 @@
 obj-$(CONFIG_ARM_CCA_GUEST) += arm-cca-guest.o
 
 arm-cca-guest-y +=  arm-cca.o
-arm-cca-guest-$(CONFIG_PCI_TSM) +=  rhi-da.o
+arm-cca-guest-$(CONFIG_PCI_TSM) +=  rhi-da.o rsi-da.o
diff --git a/drivers/virt/coco/arm-cca-guest/arm-cca.c b/drivers/virt/coco/arm-cca-guest/arm-cca.c
index 0c12aae85e6d..d4880ca59fc5 100644
--- a/drivers/virt/coco/arm-cca-guest/arm-cca.c
+++ b/drivers/virt/coco/arm-cca-guest/arm-cca.c
@@ -211,14 +211,19 @@ static struct pci_tsm *cca_tsm_lock(struct tsm_dev *tsm_dev, struct pci_dev *pde
 	if (ret)
 		return ERR_PTR(ret);
 
-	/* For now always return an error */
-	return ERR_PTR(-EIO);
+	ret = cca_device_lock(pdev);
+	if (ret)
+		return ERR_PTR(ret);
+
+	return &no_free_ptr(cca_dsc)->pci.base_tsm;
 }
 
 static void cca_tsm_unlock(struct pci_tsm *tsm)
 {
 	struct cca_guest_dsc *cca_dsc = to_cca_guest_dsc(tsm->pdev);
 
+	cca_device_unlock(tsm->pdev);
+
 	kfree(cca_dsc);
 }
 
diff --git a/drivers/virt/coco/arm-cca-guest/rsi-da.c b/drivers/virt/coco/arm-cca-guest/rsi-da.c
new file mode 100644
index 000000000000..2c3017933fb0
--- /dev/null
+++ b/drivers/virt/coco/arm-cca-guest/rsi-da.c
@@ -0,0 +1,34 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Copyright (C) 2025 ARM Ltd.
+ */
+
+#include <linux/pci.h>
+#include <asm/rsi_cmds.h>
+
+#include "rsi-da.h"
+#include "rhi-da.h"
+
+int cca_device_lock(struct pci_dev *pdev)
+{
+	int ret;
+
+	ret = rhi_vdev_set_tdi_state(pdev, RHI_DA_TDI_CONFIG_LOCKED);
+	if (ret) {
+		pci_err(pdev, "failed to lock the device (%d)\n", ret);
+		return ret;
+	}
+	return 0;
+}
+
+int cca_device_unlock(struct pci_dev *pdev)
+{
+	int ret;
+
+	ret = rhi_vdev_set_tdi_state(pdev, RHI_DA_TDI_CONFIG_UNLOCKED);
+	if (ret) {
+		pci_err(pdev, "failed to unlock the device (%d)\n", ret);
+		return ret;
+	}
+	return 0;
+}
diff --git a/drivers/virt/coco/arm-cca-guest/rsi-da.h b/drivers/virt/coco/arm-cca-guest/rsi-da.h
index 858bfdaf59c9..06fcea95d888 100644
--- a/drivers/virt/coco/arm-cca-guest/rsi-da.h
+++ b/drivers/virt/coco/arm-cca-guest/rsi-da.h
@@ -32,4 +32,7 @@ static inline int rsi_vdev_id(struct pci_dev *pdev)
 	       PCI_DEVID(pdev->bus->number, pdev->devfn);
 }
 
+int cca_device_lock(struct pci_dev *pdev);
+int cca_device_unlock(struct pci_dev *pdev);
+
 #endif
-- 
2.43.0