linux-kernel - [PATCH v1] usb: typec: tcpm: Add kernel config to wrap around tcpm logs

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Message-ID: <20230410073134.488762-1-badhri@google.com>
Date:   Mon, 10 Apr 2023 07:31:34 +0000
From:   Badhri Jagan Sridharan <badhri@...gle.com>
To:     linux@...ck-us.net, heikki.krogerus@...ux.intel.com,
        gregkh@...uxfoundation.org
Cc:     linux-usb@...r.kernel.org, linux-kernel@...r.kernel.org,
        Badhri Jagan Sridharan <badhri@...gle.com>
Subject: [PATCH v1] usb: typec: tcpm: Add kernel config to wrap around tcpm logs

This change adds CONFIG_TCPM_LOG_WRAPAROUND which when set allows the
logs to be wrapped around. Additionally, when set, does not clear
the TCPM logs when dumped.

Signed-off-by: Badhri Jagan Sridharan <badhri@...gle.com>
---
 drivers/usb/typec/tcpm/Kconfig | 6 ++++++
 drivers/usb/typec/tcpm/tcpm.c  | 9 +++++++--
 2 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/drivers/usb/typec/tcpm/Kconfig b/drivers/usb/typec/tcpm/Kconfig
index e6b88ca4a4b9..4dd2b594dfc9 100644
--- a/drivers/usb/typec/tcpm/Kconfig
+++ b/drivers/usb/typec/tcpm/Kconfig
@@ -18,6 +18,12 @@ config TYPEC_TCPCI
 	help
 	  Type-C Port Controller driver for TCPCI-compliant controller.
 
+config TCPM_LOG_WRAPAROUND
+	bool "Enable TCPM log wraparound"
+	help
+	  When set, wraps around TCPM logs and does not clear the logs when dumped. TCPM logs by
+	  default gets cleared when dumped and does not wraparound when full.
+
 if TYPEC_TCPCI
 
 config TYPEC_RT1711H
diff --git a/drivers/usb/typec/tcpm/tcpm.c b/drivers/usb/typec/tcpm/tcpm.c
index ab3a54662ed9..3f708749431b 100644
--- a/drivers/usb/typec/tcpm/tcpm.c
+++ b/drivers/usb/typec/tcpm/tcpm.c
@@ -619,7 +619,7 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
 
 	vsnprintf(tmpbuffer, sizeof(tmpbuffer), fmt, args);
 
-	if (tcpm_log_full(port)) {
+	if (!IS_ENABLED(CONFIG_TCPM_LOG_WRAPAROUND) && tcpm_log_full(port)) {
 		port->logbuffer_head = max(port->logbuffer_head - 1, 0);
 		strcpy(tmpbuffer, "overflow");
 	}
@@ -644,6 +644,10 @@ static void _tcpm_log(struct tcpm_port *port, const char *fmt, va_list args)
 		  tmpbuffer);
 	port->logbuffer_head = (port->logbuffer_head + 1) % LOG_BUFFER_ENTRIES;
 
+	if (IS_ENABLED(CONFIG_TCPM_LOG_WRAPAROUND) && port->logbuffer_head == port->logbuffer_tail)
+		port->logbuffer_tail =
+			(port->logbuffer_tail + 1) % LOG_BUFFER_ENTRIES;
+
 abort:
 	mutex_unlock(&port->logbuffer_lock);
 }
@@ -746,7 +750,8 @@ static int tcpm_debug_show(struct seq_file *s, void *v)
 		seq_printf(s, "%s\n", port->logbuffer[tail]);
 		tail = (tail + 1) % LOG_BUFFER_ENTRIES;
 	}
-	if (!seq_has_overflowed(s))
+
+	if (!IS_ENABLED(CONFIG_TCPM_LOG_WRAPAROUND) && !seq_has_overflowed(s))
 		port->logbuffer_tail = tail;
 	mutex_unlock(&port->logbuffer_lock);
 
-- 
2.40.0.577.gac1e443424-goog