tee: amdtee: check TEE status during driver initialization

The AMD-TEE driver should check if TEE is available before
registering itself with TEE subsystem. This ensures that
there is a TEE which the driver can talk to before proceeding
with tee device node allocation.

Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
Co-developed-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
Signed-off-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
Signed-off-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
Reviewed-by: Gary R Hook <gary.hook@amd.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>

drivers/crypto/ccp/tee-dev.c

@@ -362,3 +362,14 @@ int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
 	return 0;
 }
 EXPORT_SYMBOL(psp_tee_process_cmd);
+
+int psp_check_tee_status(void)
+{
+	struct psp_device *psp = psp_get_master_device();
+
+	if (!psp || !psp->tee_data)
+		return -ENODEV;
+
+	return 0;
+}
+EXPORT_SYMBOL(psp_check_tee_status);

drivers/tee/amdtee/core.c

@@ -16,6 +16,7 @@
 #include <linux/firmware.h>
 #include "amdtee_private.h"
 #include "../tee_private.h"
+#include <linux/psp-tee.h>
 
 static struct amdtee_driver_data *drv_data;
 static DEFINE_MUTEX(session_list_mutex);
@@ -438,6 +439,10 @@ static int __init amdtee_driver_init(void)
 	struct tee_shm_pool *pool = ERR_PTR(-EINVAL);
 	int rc;
 
+	rc = psp_check_tee_status();
+	if (rc)
+		goto err_fail;
+
 	drv_data = kzalloc(sizeof(*drv_data), GFP_KERNEL);
 	if (IS_ERR(drv_data))
 		return -ENOMEM;
@@ -485,6 +490,7 @@ static int __init amdtee_driver_init(void)
 	kfree(drv_data);
 	drv_data = NULL;
 
+err_fail:
 	pr_err("amd-tee driver initialization failed\n");
 	return rc;
 }

include/linux/psp-tee.h

@@ -62,6 +62,19 @@ enum tee_cmd_id {
 int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
 			u32 *status);
 
+/**
+ * psp_check_tee_status() - Checks whether there is a TEE which a driver can
+ * talk to.
+ *
+ * This function can be used by AMD-TEE driver to query if there is TEE with
+ * which it can communicate.
+ *
+ * Returns:
+ * 0          if the device has TEE
+ * -%ENODEV   if there is no TEE available
+ */
+int psp_check_tee_status(void);
+
 #else /* !CONFIG_CRYPTO_DEV_SP_PSP */
 
 static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
@@ -69,5 +82,10 @@ static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
 {
 	return -ENODEV;
 }
+
+static inline int psp_check_tee_status(void)
+{
+	return -ENODEV;
+}
 #endif /* CONFIG_CRYPTO_DEV_SP_PSP */
 #endif /* __PSP_TEE_H_ */