[PATCH net-next 3/6] eth: fbnic: Create ring buffer for firmware logs

[Lee Trager <lee@trager.us>]

When enabled, firmware may send logs messages which are specific to the
device and not the host. Create a ring buffer to store these messages
which are read by a user through DebugFS. Buffer access is protected by
a spinlock.

Signed-off-by: Lee Trager <lee@trager.us>
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
---
 drivers/net/ethernet/meta/fbnic/Makefile      |  1 +
 drivers/net/ethernet/meta/fbnic/fbnic.h       |  3 +
 .../net/ethernet/meta/fbnic/fbnic_fw_log.c    | 95 +++++++++++++++++++
 .../net/ethernet/meta/fbnic/fbnic_fw_log.h    | 43 +++++++++
 4 files changed, 142 insertions(+)
 create mode 100644 drivers/net/ethernet/meta/fbnic/fbnic_fw_log.c
 create mode 100644 drivers/net/ethernet/meta/fbnic/fbnic_fw_log.h

diff --git a/drivers/net/ethernet/meta/fbnic/Makefile b/drivers/net/ethernet/meta/fbnic/Makefile
index 0dbc634adb4b..15e8ff649615 100644
--- a/drivers/net/ethernet/meta/fbnic/Makefile
+++ b/drivers/net/ethernet/meta/fbnic/Makefile
@@ -12,6 +12,7 @@ fbnic-y := fbnic_csr.o \
 	   fbnic_devlink.o \
 	   fbnic_ethtool.o \
 	   fbnic_fw.o \
+	   fbnic_fw_log.o \
 	   fbnic_hw_stats.o \
 	   fbnic_hwmon.o \
 	   fbnic_irq.o \
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic.h b/drivers/net/ethernet/meta/fbnic/fbnic.h
index 65815d4f379e..c376e06880c9 100644
--- a/drivers/net/ethernet/meta/fbnic/fbnic.h
+++ b/drivers/net/ethernet/meta/fbnic/fbnic.h
@@ -12,6 +12,7 @@

 #include "fbnic_csr.h"
 #include "fbnic_fw.h"
+#include "fbnic_fw_log.h"
 #include "fbnic_hw_stats.h"
 #include "fbnic_mac.h"
 #include "fbnic_rpc.h"
@@ -85,6 +86,8 @@ struct fbnic_dev {

 	/* Lock protecting access to hw_stats */
 	spinlock_t hw_stats_lock;
+
+	struct fbnic_fw_log fw_log;
 };

 /* Reserve entry 0 in the MSI-X "others" array until we have filled all
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.c b/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.c
new file mode 100644
index 000000000000..caedbe7844f7
--- /dev/null
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.c
@@ -0,0 +1,95 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Copyright (c) Meta Platforms, Inc. and affiliates. */
+
+#include <linux/spinlock.h>
+#include <linux/vmalloc.h>
+
+#include "fbnic.h"
+#include "fbnic_fw.h"
+#include "fbnic_fw_log.h"
+
+int fbnic_fw_log_init(struct fbnic_dev *fbd)
+{
+	struct fbnic_fw_log *log = &fbd->fw_log;
+	void *data;
+
+	if (WARN_ON_ONCE(fbnic_fw_log_ready(fbd)))
+		return -EEXIST;
+
+	data = vmalloc(FBNIC_FW_LOG_SIZE);
+	if (!data)
+		return -ENOMEM;
+
+	spin_lock_init(&fbd->fw_log.lock);
+	INIT_LIST_HEAD(&log->entries);
+	log->size = FBNIC_FW_LOG_SIZE;
+	log->data_start = data;
+	log->data_end = data + FBNIC_FW_LOG_SIZE;
+
+	return 0;
+}
+
+void fbnic_fw_log_free(struct fbnic_dev *fbd)
+{
+	struct fbnic_fw_log *log = &fbd->fw_log;
+
+	if (!fbnic_fw_log_ready(fbd))
+		return;
+
+	INIT_LIST_HEAD(&log->entries);
+	log->size = 0;
+	vfree(log->data_start);
+	log->data_start = NULL;
+	log->data_end = NULL;
+}
+
+int fbnic_fw_log_write(struct fbnic_dev *fbd, u64 index, u32 timestamp,
+		       char *msg)
+{
+	struct fbnic_fw_log_entry *entry, *head, *tail, *next;
+	struct fbnic_fw_log *log = &fbd->fw_log;
+	size_t msg_len = strlen(msg) + 1;
+	unsigned long flags;
+	void *entry_end;
+
+	if (!fbnic_fw_log_ready(fbd)) {
+		dev_err(fbd->dev, "Firmware sent log entry without being requested!\n");
+		return -ENOSPC;
+	}
+
+	spin_lock_irqsave(&log->lock, flags);
+
+	if (list_empty(&log->entries)) {
+		entry = log->data_start;
+	} else {
+		head = list_first_entry(&log->entries, typeof(*head), list);
+		entry = (struct fbnic_fw_log_entry *)&head->msg[head->len + 1];
+		entry = PTR_ALIGN(entry, 8);
+	}
+
+	entry_end = &entry->msg[msg_len + 1];
+
+	/* We've reached the end of the buffer, wrap around */
+	if (entry_end > log->data_end) {
+		entry = log->data_start;
+		entry_end = &entry->msg[msg_len + 1];
+	}
+
+	/* Make room for entry by removing from tail. */
+	list_for_each_entry_safe_reverse(tail, next, &log->entries, list) {
+		if (entry <= tail && entry_end > (void *)tail)
+			list_del(&tail->list);
+		else
+			break;
+	}
+
+	entry->index = index;
+	entry->timestamp = timestamp;
+	entry->len = msg_len;
+	strscpy(entry->msg, msg, entry->len);
+	list_add(&entry->list, &log->entries);
+
+	spin_unlock_irqrestore(&log->lock, flags);
+
+	return 0;
+}
diff --git a/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.h b/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.h
new file mode 100644
index 000000000000..881ee298ede7
--- /dev/null
+++ b/drivers/net/ethernet/meta/fbnic/fbnic_fw_log.h
@@ -0,0 +1,43 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* Copyright (c) Meta Platforms, Inc. and affiliates. */
+
+#ifndef _FBNIC_FW_LOG_H_
+#define _FBNIC_FW_LOG_H_
+
+#include <linux/spinlock.h>
+#include <linux/types.h>
+
+/* A 512K log buffer was chosen fairly arbitrarily */
+#define FBNIC_FW_LOG_SIZE	(512 * 1024) /* bytes */
+
+/* Firmware log output is prepended with log index followed by a timestamp.
+ * The timestamp is similar to Zephyr's format DD:HH:MM:SS.MMM
+ */
+#define FBNIC_FW_LOG_FMT	"[%5lld] [%02ld:%02ld:%02ld:%02ld.%03ld] %s\n"
+
+struct fbnic_dev;
+
+struct fbnic_fw_log_entry {
+	struct list_head	list;
+	u64			index;
+	u32			timestamp;
+	u16			len;
+	char			msg[] __counted_by(len);
+};
+
+struct fbnic_fw_log {
+	void			*data_start;
+	void			*data_end;
+	size_t			size;
+	struct list_head	entries;
+	/* Spin lock for accessing or modifying entries */
+	spinlock_t		lock;
+};
+
+#define fbnic_fw_log_ready(_fbd)	(!!(_fbd)->fw_log.data_start)
+
+int fbnic_fw_log_init(struct fbnic_dev *fbd);
+void fbnic_fw_log_free(struct fbnic_dev *fbd);
+int fbnic_fw_log_write(struct fbnic_dev *fbd, u64 index, u32 timestamp,
+		       char *msg);
+#endif /* _FBNIC_FW_LOG_H_ */
--
2.47.1