linux-kernel - [PATCH v1 1/1] tpm_ffa_crb: handle tpm busy return code

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Message-ID: <20250609141600.3601340-2-prachotan.bathi@arm.com>
Date: Mon,  9 Jun 2025 09:16:00 -0500
From: Prachotan Bathi <prachotan.bathi@....com>
To: Peter Huewe <peterhuewe@....de>,
	Jarkko Sakkinen <jarkko@...nel.org>,
	Jason Gunthorpe <jgg@...pe.ca>,
	Stuart Yoder <stuart.yoder@....com>
Cc: linux-integrity@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Prachotan Bathi <prachotan.bathi@....com>
Subject: [PATCH v1 1/1] tpm_ffa_crb: handle tpm busy return code

Platforms supporting direct message request v2 can
support SPs that support multiple services.
If the TPM service is sharing the SP with another service,
it could get an error code of BUSY if the other service is
in process.
This patch adds a parameterized variable (default 2000ms)
 that indicates the maximum time to keep retrying for.

Signed-off-by: Prachotan Bathi <prachotan.bathi@....com>
---
 drivers/char/tpm/tpm_crb_ffa.c | 74 +++++++++++++++++++++++-----------
 1 file changed, 50 insertions(+), 24 deletions(-)

diff --git a/drivers/char/tpm/tpm_crb_ffa.c b/drivers/char/tpm/tpm_crb_ffa.c
index 4ead61f01299..e47e110bac9e 100644
--- a/drivers/char/tpm/tpm_crb_ffa.c
+++ b/drivers/char/tpm/tpm_crb_ffa.c
@@ -10,6 +10,8 @@
 #define pr_fmt(fmt) "CRB_FFA: " fmt
 
 #include <linux/arm_ffa.h>
+#include <linux/delay.h>
+#include <linux/moduleparam.h>
 #include "tpm_crb_ffa.h"
 
 /* TPM service function status codes */
@@ -178,6 +180,17 @@ int tpm_crb_ffa_init(void)
 }
 EXPORT_SYMBOL_GPL(tpm_crb_ffa_init);
 
+static unsigned int busy_timeout = 2000;
+/**
+ * busy_timeout - Maximum time to retry before giving up on busy
+ *
+ * This parameter defines the maximum time in milliseconds to retry
+ * sending a message to the TPM service before giving up.
+ */
+module_param(busy_timeout, uint, 0644);
+MODULE_PARM_DESC(busy_timeout,
+		 "Maximum time to retry before giving up on busy");
+
 static int __tpm_crb_ffa_send_recieve(unsigned long func_id,
 				      unsigned long a0,
 				      unsigned long a1,
@@ -191,34 +204,47 @@ static int __tpm_crb_ffa_send_recieve(unsigned long func_id,
 
 	msg_ops = tpm_crb_ffa->ffa_dev->ops->msg_ops;
 
-	if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) {
-		memset(&tpm_crb_ffa->direct_msg_data2, 0x00,
-		       sizeof(struct ffa_send_direct_data2));
+	ktime_t start;
+	ktime_t stop;
+
+	start = ktime_get();
+	stop = ktime_add(start, ms_to_ktime(busy_timeout));
+
+	do {
+		if (ffa_partition_supports_direct_req2_recv(tpm_crb_ffa->ffa_dev)) {
+			memset(&tpm_crb_ffa->direct_msg_data2, 0x00,
+			       sizeof(struct ffa_send_direct_data2));
 
-		tpm_crb_ffa->direct_msg_data2.data[0] = func_id;
-		tpm_crb_ffa->direct_msg_data2.data[1] = a0;
-		tpm_crb_ffa->direct_msg_data2.data[2] = a1;
-		tpm_crb_ffa->direct_msg_data2.data[3] = a2;
+			tpm_crb_ffa->direct_msg_data2.data[0] = func_id;
+			tpm_crb_ffa->direct_msg_data2.data[1] = a0;
+			tpm_crb_ffa->direct_msg_data2.data[2] = a1;
+			tpm_crb_ffa->direct_msg_data2.data[3] = a2;
 
-		ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev,
+			ret = msg_ops->sync_send_receive2(tpm_crb_ffa->ffa_dev,
 				&tpm_crb_ffa->direct_msg_data2);
-		if (!ret)
-			ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]);
-	} else {
-		memset(&tpm_crb_ffa->direct_msg_data, 0x00,
-		       sizeof(struct ffa_send_direct_data));
-
-		tpm_crb_ffa->direct_msg_data.data1 = func_id;
-		tpm_crb_ffa->direct_msg_data.data2 = a0;
-		tpm_crb_ffa->direct_msg_data.data3 = a1;
-		tpm_crb_ffa->direct_msg_data.data4 = a2;
-
-		ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev,
-				&tpm_crb_ffa->direct_msg_data);
-		if (!ret)
-			ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1);
-	}
+			if (!ret)
+				ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data2.data[0]);
+		} else {
+			memset(&tpm_crb_ffa->direct_msg_data, 0x00,
+			       sizeof(struct ffa_send_direct_data));
 
+			tpm_crb_ffa->direct_msg_data.data1 = func_id;
+			tpm_crb_ffa->direct_msg_data.data2 = a0;
+			tpm_crb_ffa->direct_msg_data.data3 = a1;
+			tpm_crb_ffa->direct_msg_data.data4 = a2;
+
+			ret = msg_ops->sync_send_receive(tpm_crb_ffa->ffa_dev,
+				&tpm_crb_ffa->direct_msg_data);
+			if (!ret)
+				ret = tpm_crb_ffa_to_linux_errno(tpm_crb_ffa->direct_msg_data.data1);
+		}
+		if (ret == -EBUSY)
+			pr_err("TPM says busy, trying again, value, ret: %d\n",
+			       ret);
+		else
+			break;
+		usleep_range(50, 100);
+	} while (ktime_before(ktime_get(), stop));
 
 	return ret;
 }
-- 
2.43.0