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>

1 files changed, 18 insertions, 0 deletions

diff --git a/include/linux/psp-tee.h b/include/linux/psp-tee.h
index 63bb2212fce0..cb0c95d6d76b 100644
--- a/include/linux/psp-tee.h
+++ b/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_ */