Refactor the i8042 module to be thread-safe.

Any command/data coming from host will be placed in from_host queue, and
the interrupt handler returns immediately. The i8042_command_task() will
handle them later.

Data reply to the host will be protected by the mutex.

BUG=chrome-os-partner:10090
TEST=randomly play around on the link board.

Change-Id: Ic19d5abd1abf8dc261ddaad4224cd9305c2f36a4
Signed-off-by: Louis Yung-Chieh Lo <yjlou@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/24299
Commit-Ready: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>
Reviewed-by: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>
Tested-by: Yung-Chieh Lo <yjlou%chromium.org@gtempaccount.com>

4 files changed, 182 insertions, 58 deletions

diff --git a/common/build.mk b/common/build.mk
index f32e945113..5fdfabb061 100644
--- a/common/build.mk
+++ b/common/build.mk
@@ -8,7 +8,7 @@
 
 common-y=main.o util.o console.o uart_buffering.o
 common-y+=memory_commands.o shared_mem.o system_common.o hooks.o
-common-y+=gpio_commands.o version.o printf.o
+common-y+=gpio_commands.o version.o printf.o queue.o
 common-$(CONFIG_BATTERY_ATL706486)+=battery_atl706486.o
 common-$(CONFIG_CHARGER_BQ24725)+=charger_bq24725.o
 common-$(CONFIG_PMU_TPS65090)+=pmu_tps65090.o
diff --git a/common/i8042.c b/common/i8042.c
index 8032e900cc..0174e84f0b 100644
--- a/common/i8042.c
+++ b/common/i8042.c
@@ -11,6 +11,7 @@
 #include "i8042.h"
 #include "keyboard.h"
 #include "lpc.h"
+#include "queue.h"
 #include "task.h"
 #include "timer.h"
 #include "util.h"
@@ -30,71 +31,69 @@
 #define CPRINTF5(format, args...)
 #endif
 
-#define MAX_QUEUED_KEY_PRESS 16
 
-/* Circular buffer to host.
- * head: next to dequeqe
- * tail: next to enqueue
- * head == tail: empty.
- * tail + 1 == head: full
- */
-static int head_to_buffer = 0;
-static int tail_to_buffer = 0;
-#define HOST_BUFFER_SIZE (16)
-static uint8_t to_host_buffer[HOST_BUFFER_SIZE];
+static int i8042_irq_enabled;
+
+
+static struct mutex to_host_mutex;
+static uint8_t to_host_buffer[16];
+static struct queue to_host = {
+	.buf_bytes  = ARRAY_SIZE(to_host_buffer),
+	.unit_bytes = sizeof(uint8_t),
+	.buf        = to_host_buffer,
+};
 
-static int i8042_irq_enabled = 0;
+/* Queue command/data from the host */
+enum {
+	HOST_COMMAND = 0,
+	HOST_DATA,
+};
+struct host_byte {
+	uint8_t type;
+	uint8_t byte;
+};
+/* 4 is big enough for all i8042 commands */
+static uint8_t from_host_buffer[4 * sizeof(struct host_byte)];
+static struct queue from_host = {
+	.buf_bytes  = ARRAY_SIZE(from_host_buffer),
+	.unit_bytes = sizeof(struct host_byte),
+	.buf        = from_host_buffer,
+};
 
 
 /* Reset all i8042 buffer */
 void i8042_flush_buffer()
 {
-	head_to_buffer = tail_to_buffer = 0;
+	queue_reset(&to_host);
 	lpc_keyboard_clear_buffer();
 }
 
 
-/* Called by the chip-specific code when host sedns a byte to port 0x60. */
+/* Called by the chip-specific code when host sends a byte to port 0x60.
+ * Note that this is in the interrupt context.
+ */
 void i8042_receives_data(int data)
 {
-	int ret_len;
-	uint8_t output[MAX_SCAN_CODE_LEN];
-	enum ec_error_list ret;
+	struct host_byte h;
 
-	ret_len = handle_keyboard_data(data, output);
-	ret = i8042_send_to_host(ret_len, output);
-	ASSERT(ret == EC_SUCCESS);
+	h.type = HOST_DATA;
+	h.byte = data;
+	queue_add_units(&from_host, &h, 1);
+	task_wake(TASK_ID_I8042CMD);
 }
 
 
-/* Called by the chip-specific code when host sedns a byte to port 0x64. */
+/* Called by the chip-specific code when host sends a byte to port 0x64.
+ * Note that this is in the interrupt context.
+ */
 void i8042_receives_command(int cmd)
 {
-	int ret_len;
-	uint8_t output[MAX_SCAN_CODE_LEN];
-	enum ec_error_list ret;
-
-	ret_len = handle_keyboard_command(cmd, output);
-	ret = i8042_send_to_host(ret_len, output);
-	ASSERT(ret == EC_SUCCESS);
-}
-
-
-/* Called by EC common code to send bytes to host via port 0x60. */
-static void enq_to_host(int len, const uint8_t *to_host)
-{
-	int from, to;
+	struct host_byte h;
 
-	/* Check if the buffer has enough space, then copy them to buffer. */
-	if ((tail_to_buffer + len) <= (head_to_buffer + HOST_BUFFER_SIZE - 1)) {
-		for (from = 0, to = tail_to_buffer; from < len;) {
-			kblog_put('t', to);
-			kblog_put('T', to_host[from]);
-			to_host_buffer[to++] = to_host[from++];
-			to %= HOST_BUFFER_SIZE;
-		}
-		tail_to_buffer = (tail_to_buffer + len) % HOST_BUFFER_SIZE;
-	}
+	h.type = HOST_COMMAND;
+	h.byte = cmd;
+	queue_add_units(&from_host, &h, 1);
+	task_wake(TASK_ID_I8042CMD);
 }
 
 
@@ -111,6 +110,24 @@ void i8042_disable_keyboard_irq(void) {
 }
 
 
+static void i8042_handle_from_host(void)
+{
+	struct host_byte h;
+	int ret_len;
+	uint8_t output[MAX_SCAN_CODE_LEN];
+	enum ec_error_list ret;
+
+	while (queue_remove_unit(&from_host, &h)) {
+		if (h.type == HOST_COMMAND)
+			ret_len = handle_keyboard_command(h.byte, output);
+		else
+			ret_len = handle_keyboard_data(h.byte, output);
+
+		ret = i8042_send_to_host(ret_len, output);
+		ASSERT(ret == EC_SUCCESS);
+	}
+}
+
 void i8042_command_task(void)
 {
 	while (1) {
@@ -119,13 +136,13 @@ void i8042_command_task(void)
 
 		while (1) {
 			uint8_t chr;
-			int empty = 0;
+
+			/* first handle command/data from host. */
+			i8042_handle_from_host();
 
 			/* Check if we have data in buffer to host. */
-			if (head_to_buffer == tail_to_buffer) {
-				empty = 1;  /* nothing to host */
-			}
-			if (empty) break;
+			if (queue_is_empty(&to_host))
+				break;  /* nothing to host */
 
 			/* if the host still didn't read that away,
 			   try next time. */
@@ -137,11 +154,9 @@ void i8042_command_task(void)
 			}
 
 			/* Get a char from buffer. */
-			chr = to_host_buffer[head_to_buffer];
-			kblog_put('k', head_to_buffer);
+			kblog_put('k', to_host.head);
+			queue_remove_unit(&to_host, &chr);
 			kblog_put('K', chr);
-			head_to_buffer =
-				(head_to_buffer + 1) % HOST_BUFFER_SIZE;
 
 			/* Write to host. */
 			lpc_keyboard_put_char(chr, i8042_irq_enabled);
@@ -152,15 +167,31 @@ void i8042_command_task(void)
 }
 
 
-enum ec_error_list i8042_send_to_host(int len, const uint8_t *to_host)
+static void enq_to_host(int len, const uint8_t *bytes)
+{
+	int i;
+
+	mutex_lock(&to_host_mutex);
+	/* Check if the buffer has enough space, then copy them to buffer. */
+	if (queue_has_space(&to_host, len)) {
+		for (i = 0; i < len; ++i) {
+			kblog_put('t', to_host.tail);
+			kblog_put('T', bytes[i]);
+		}
+		queue_add_units(&to_host, bytes, len);
+	}
+	mutex_unlock(&to_host_mutex);
+}
+
+enum ec_error_list i8042_send_to_host(int len, const uint8_t *bytes)
 {
 	int i;
 
 	for (i = 0; i < len; i++)
-		kblog_put('s', to_host[i]);
+		kblog_put('s', bytes[i]);
 
 	/* Put to queue in memory */
-	enq_to_host(len, to_host);
+	enq_to_host(len, bytes);
 
 	/* Wake up the task to move from queue to the buffer to host. */
 	task_wake(TASK_ID_I8042CMD);
diff --git a/common/queue.c b/common/queue.c
new file mode 100644
index 0000000000..8018e4c0b0
--- /dev/null
+++ b/common/queue.c
@@ -0,0 +1,53 @@
+/* Copyright (c) 2012 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.
+ *
+ * Queue data structure implementation.
+ */
+#include "queue.h"
+#include "util.h"
+
+void queue_reset(struct queue *queue)
+{
+	queue->head = queue->tail = 0;
+}
+
+int queue_is_empty(const struct queue *q)
+{
+	return q->head == q->tail;
+}
+
+int queue_has_space(const struct queue *q, int unit_count)
+{
+	return (q->tail + unit_count * q->unit_bytes) <=
+	       (q->head + q->buf_bytes - q->unit_bytes);
+}
+
+void queue_add_units(struct queue *q, const void *src, int unit_count)
+{
+	const uint8_t *s = (const uint8_t *)src;
+
+	if (!queue_has_space(q, unit_count))
+		return;
+
+	for (unit_count *= q->unit_bytes; unit_count; unit_count--) {
+		q->buf[q->tail++] = *(s++);
+		q->tail %= q->buf_bytes;
+	}
+}
+
+int queue_remove_unit(struct queue *q, void *dest)
+{
+	int count;
+	uint8_t *d = (uint8_t *)dest;
+
+	if (queue_is_empty(q))
+		return 0;
+
+	for (count = q->unit_bytes; count; count--) {
+		*(d++) = q->buf[q->head++];
+		q->head %= q->buf_bytes;
+	}
+
+	return 1;
+}
diff --git a/include/queue.h b/include/queue.h
new file mode 100644
index 0000000000..2c967ee4a8
--- /dev/null
+++ b/include/queue.h
@@ -0,0 +1,40 @@
+/* Copyright (c) 2012 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.
+ *
+ * Queue data structure.
+ */
+
+#include "common.h"
+
+/* Generic queue container.
+ *
+ *   head: next to dequeqe
+ *   tail: next to enqueue
+ *
+ *   Empty:
+ *     head == tail
+ *   Full:
+ *     ((tail + 1) % buf_bytes) == head
+ */
+struct queue {
+	int head, tail;
+	int buf_bytes;   /* size of buffer (in byte) */
+	int unit_bytes;  /* size of unit (in byte) */
+	uint8_t *buf;
+};
+
+/* Reset the queue to empty state. */
+void queue_reset(struct queue *queue);
+
+/* Return TRUE if the queue is empty. */
+int queue_is_empty(const struct queue *q);
+
+/* Return TRUE if the queue has at least one unit space. */
+int queue_has_space(const struct queue *q, int unit_count);
+
+/* Add multiple units into queue. */
+void queue_add_units(struct queue *q, const void *src, int unit_count);
+
+/* Remove one unit from the begin of the queue. */
+int queue_remove_unit(struct queue *q, void *dest);