linux-kernel - [PATCH v2] tpm_crb: ffa_tpm: fix/update comments describing the CRB over FFA ABI

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Message-Id: <20250430154723.1025101-1-stuart.yoder@arm.com>
Date: Wed, 30 Apr 2025 10:47:23 -0500
From: Stuart Yoder <stuart.yoder@....com>
To: linux-integrity@...r.kernel.org,
	jarkko@...nel.org,
	peterhuewe@....de,
	jgg@...pe.ca,
	sudeep.holla@....com
Cc: linux-kernel@...r.kernel.org
Subject: [PATCH v2] tpm_crb: ffa_tpm: fix/update comments describing the CRB over FFA ABI

-Fix the comment describing the 'start' function, which was a cut/paste
 mistake for a different function.

-The comment for DIRECT_REQ and DIRECT_RESP only mentioned AArch32
 and listed 32-bit function IDs.  Update to include 64-bit.

Signed-off-by: Stuart Yoder <stuart.yoder@....com>
---
v2:
  -squashed the two comment updates into a single patch

 drivers/char/tpm/tpm_crb_ffa.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 3169a87a56b60..134747911ba38 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -38,9 +38,11 @@
  * messages.
  *
  * All requests with FFA_MSG_SEND_DIRECT_REQ and FFA_MSG_SEND_DIRECT_RESP
- * are using the AArch32 SMC calling convention with register usage as
- * defined in FF-A specification:
- * w0:    Function ID (0x8400006F or 0x84000070)
+ * are using the AArch32 or AArch64 SMC calling convention with register usage
+ * as defined in FF-A specification:
+ * w0:    Function ID
+ *          -for 32-bit: 0x8400006F or 0x84000070
+ *          -for 64-bit: 0xC400006F or 0xC4000070
  * w1:    Source/Destination IDs
  * w2:    Reserved (MBZ)
  * w3-w7: Implementation defined, free to be used below
@@ -68,7 +70,8 @@
 #define CRB_FFA_GET_INTERFACE_VERSION 0x0f000001
 
 /*
- * Return information on a given feature of the TPM service
+ * Notifies the TPM service that a TPM command or TPM locality request is
+ * ready to be processed, and allows the TPM service to process it.
  * Call register usage:
  * w3:    Not used (MBZ)
  * w4:    TPM service function ID, CRB_FFA_START
-- 
2.34.1