Add PD events logging

Add a FIFO to log important events on the PD MCU and coming from the PD
accessories.

The retrieval of the accessories log from the accessories by the PD MCU
is not implemented yet.

Signed-off-by: Vincent Palatin <vpalatin@chromium.org>

BRANCH=samus
BUG=chrome-os-partner:32785
TEST=execute "ectool --name=cros_pd pdlog"
before and after plugging Zinger charger.

Change-Id: If96d73e711ff6ad64cfb99bd3e4d2d8f2643f19a
Reviewed-on: https://chromium-review.googlesource.com/238854
Tested-by: Vincent Palatin <vpalatin@chromium.org>
Reviewed-by: Alec Berg <alecaberg@chromium.org>
Commit-Queue: Vincent Palatin <vpalatin@chromium.org>
Trybot-Ready: Vincent Palatin <vpalatin@chromium.org>

1 files changed, 151 insertions, 0 deletions

diff --git a/common/pd_log.c b/common/pd_log.c
new file mode 100644
index 0000000000..e48b763b6c
--- /dev/null
+++ b/common/pd_log.c
@@ -0,0 +1,151 @@
+/* Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "console.h"
+#include "hooks.h"
+#include "host_command.h"
+#include "task.h"
+#include "timer.h"
+#include "util.h"
+
+/* Event log FIFO */
+#define UNIT_SIZE sizeof(struct ec_response_pd_log)
+#define LOG_SIZE (CONFIG_USB_PD_LOG_SIZE/UNIT_SIZE)
+static struct ec_response_pd_log log_events[LOG_SIZE];
+BUILD_ASSERT(POWER_OF_TWO(LOG_SIZE));
+/*
+ * The FIFO pointers are defined as following :
+ * "log_head" is the next available event to dequeue.
+ * "log_tail" is marking the end of the FIFO content (after last commited event)
+ * "log_tail_next" is the next available spot to enqueue events.
+ * The pointers are not wrapped until they are used, so we don't need an extra
+ * entry to disambiguate between full and empty FIFO.
+ *
+ * For concurrency, several tasks might try to enqueue events in parallel with
+ * pd_log_event(). Only one task is dequeuing events (host commands or VDM).
+ * When the FIFO is full, pd_log_event() will discard the oldest events,
+ * so "log_head" is incremented/decremented in a critical section since it is
+ * accessed from both pd_log_event() and pd_log_dequeue().
+ * log_tail_next is also protected as several writers can race to add an event
+ * to the queue.
+ * When a writer is done adding its event, it is updating log_tail,
+ * so the event can be consumed by pd_log_dequeue().
+ */
+static size_t log_head;
+static size_t log_tail;
+static size_t log_tail_next;
+
+/* Size of one FIFO entry */
+#define ENTRY_SIZE(payload_sz) (1+DIV_ROUND_UP((payload_sz), UNIT_SIZE))
+
+void pd_log_event(uint8_t type, uint8_t size_port,
+		  uint16_t data, void *payload)
+{
+	struct ec_response_pd_log *r;
+	size_t payload_size = PD_LOG_SIZE(size_port);
+	size_t total_size = ENTRY_SIZE(payload_size);
+	size_t current_tail, first;
+
+	/* --- critical section : reserve queue space --- */
+	interrupt_disable();
+	current_tail = log_tail_next;
+	log_tail_next = current_tail + total_size;
+	interrupt_enable();
+	/* --- end of critical section --- */
+
+	/* Out of space : discard the oldest entry */
+	while ((LOG_SIZE - (current_tail - log_head)) < total_size) {
+		struct ec_response_pd_log *oldest;
+		/* --- critical section : atomically free-up space --- */
+		interrupt_disable();
+		oldest = log_events + (log_head & (LOG_SIZE - 1));
+		log_head += ENTRY_SIZE(PD_LOG_SIZE(oldest->size_port));
+		interrupt_enable();
+		/* --- end of critical section --- */
+	}
+
+	r = log_events + (current_tail & (LOG_SIZE - 1));
+
+	r->timestamp = get_time().val >> PD_LOG_TIMESTAMP_SHIFT;
+	r->type = type;
+	r->size_port = size_port;
+	r->data = data;
+	/* copy the payload into the FIFO */
+	first = MIN(total_size - 1, (LOG_SIZE -
+		    (current_tail & (LOG_SIZE - 1))) - 1);
+	if (first)
+		memcpy(r->payload, payload, first * UNIT_SIZE);
+	if (first < total_size - 1)
+		memcpy(log_events, ((uint8_t *)payload) + first * UNIT_SIZE,
+			(total_size - first) * UNIT_SIZE);
+	/* mark the entry available in the queue if nobody is behind us */
+	if (current_tail == log_tail)
+		log_tail = log_tail_next;
+}
+
+static int pd_log_dequeue(struct ec_response_pd_log *r)
+{
+	uint32_t now = get_time().val >> PD_LOG_TIMESTAMP_SHIFT;
+	unsigned total_size, first;
+	struct ec_response_pd_log *entry;
+	size_t current_head;
+
+retry:
+	current_head = log_head;
+	/* The log FIFO is empty */
+	if (log_tail == current_head) {
+		memset(r, 0, UNIT_SIZE);
+		r->type = PD_EVENT_NO_ENTRY;
+		return UNIT_SIZE;
+	}
+
+	entry = log_events + (current_head & (LOG_SIZE - 1));
+	total_size = ENTRY_SIZE(PD_LOG_SIZE(entry->size_port));
+	first = MIN(total_size, LOG_SIZE - (current_head & (LOG_SIZE - 1)));
+	memcpy(r, entry, first * UNIT_SIZE);
+	if (first < total_size)
+		memcpy(r + first, log_events, (total_size-first) * UNIT_SIZE);
+
+	/* --- critical section : remove the entry from the queue --- */
+	interrupt_disable();
+	if (log_head != current_head) { /* our entry was thrown away */
+		interrupt_enable();
+		goto retry;
+	}
+	log_head += total_size;
+	interrupt_enable();
+	/* --- end of critical section --- */
+
+	/* fixup the timestamp : number of milliseconds in the past */
+	r->timestamp = now - r->timestamp;
+
+	return total_size * UNIT_SIZE;
+}
+
+#ifdef HAS_TASK_HOSTCMD
+/* we are a PD MCU/EC, send back the events to the host */
+static int hc_pd_get_log_entry(struct host_cmd_handler_args *args)
+{
+	struct ec_response_pd_log *r = args->response;
+
+	args->response_size = pd_log_dequeue(r);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_PD_GET_LOG_ENTRY,
+		     hc_pd_get_log_entry,
+		     EC_VER_MASK(0));
+#else /* !HAS_TASK_HOSTCMD */
+/* we are a PD accessory, send back the events as a VDM (VDO_CMD_GET_LOG) */
+int pd_vdm_get_log_entry(uint32_t *payload)
+{
+	struct ec_response_pd_log *r = (void *)&payload[1];
+	int byte_size;
+
+	byte_size = pd_log_dequeue(r);
+
+	return 1 + DIV_ROUND_UP(byte_size, sizeof(uint32_t));
+}
+#endif /* !HAS_TASK_HOSTCMD */