EC-CR50 communication

This patch supports EC-CR50 communication.
EC activates EC-CR50 communication by setting high DIOB3, and send
a command packet to CR50 through UART_EC_TX_CR50_RX. Cr50 processes
the packet, and sends a response packet back to EC. EC deactivates
EC-CR50 communication by putting low DIOB3.

This patch supports two kinds of EC-CR50 commands:
- CR50_COMM_CMD_SET_BOOT_MODE
- CR50_COMM_CMD_VERIFY_HASH

Cr50 stores some of EC-EFS context in a powerdown register before
deep sleep and restores it after wakeup.

This patch increases flash usage by 1456 bytes.

BUG=b:119329144
BRANCH=cr50
TEST=Checked "ec_comm" console command on Octopus and
reworked Helios.
Checked uart_stress_tester.py running without character loss.

Change-Id: I23e90b9f3e860a3d198dcee718d7d11080d06e40
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/1961145
Reviewed-by: Daisuke Nojiri <dnojiri@chromium.org>
(cherry picked from commit 5a8a856b0a942d3b982ef28324a924db3c7d9f40)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2122641
Tested-by: Mary Ruthven <mruthven@chromium.org>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>
Commit-Queue: Mary Ruthven <mruthven@chromium.org>
(cherry picked from commit 2f7cd52f09c1ab8417b45c0da49a58f322bc2d92)
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2165782

2 files changed, 26 insertions, 10 deletions

diff --git a/chip/g/init_chip.h b/chip/g/init_chip.h
index 506dfeab21..a5c08cd3d9 100644
--- a/chip/g/init_chip.h
+++ b/chip/g/init_chip.h
@@ -23,6 +23,7 @@
  *	SCRATCH17 - deep sleep count
  *	SCRATCH18 - Preserving USB_DCFG through deep sleep
  *	SCRATCH19 - Preserving USB data sequencing PID through deep sleep
+ *	SCRATCH20 - Preserving EC-EFS context
  *
  * PWRDN_SCRATCH 28 - 31 - Reserved for boot rom
  */
diff --git a/chip/g/usart.c b/chip/g/usart.c
index b597cb3f93..4329a673bc 100644
--- a/chip/g/usart.c
+++ b/chip/g/usart.c
@@ -167,7 +167,7 @@ void get_data_from_usb(struct usart_config const *config)
 #ifdef BOARD_CR50
 	if (config->uart == UART_EC) {
 		/*
-		 * If USB-to-UART bridging is disabled, drop all input data.
+		 * If USB-to-UART bridging is disabled, do not forward data.
 		 * Otherwise, data could be pushed into UART TX FIFO, and
 		 * transferred to EC eventually once EC-CR50 communication
 		 * enables EC UART.
@@ -204,14 +204,35 @@ void send_data_to_usb(struct usart_config const *config)
 
 	q_room = queue_space(uart_in);
 
-	if (!q_room)
-		return;
-
 	mask = uart_in->buffer_units_mask;
 	tail = uart_in->state->tail & mask;
 	count = 0;
 
 #ifdef BOARD_CR50
+	if (ec_comm_is_uart_in_packet_mode(uart)) {
+		/*
+		 * Even if UART-to-USB data queue is full (count == q_room),
+		 * It should drain UART queue, so that an EC packet
+		 * can be processed. In this case, EC console data
+		 * shall be lost anyway.
+		 */
+		while (uartn_rx_available(uart)) {
+			uint8_t ch = uartn_read_char(uart);
+
+			if (ec_comm_process_packet(ch))
+				continue;
+
+			if ((count != q_room) && ec_bridge_enabled_) {
+				uart_in->buffer[tail] = ch;
+				tail = (tail + 1) & mask;
+				count++;
+			}
+		}
+		if (count)
+			queue_advance_tail(uart_in, count);
+		return;
+	}
+
 	/*
 	 * If UART-to-USB bridging is not allowed, do not put any output
 	 * data to uart_in queue.
@@ -219,12 +240,6 @@ void send_data_to_usb(struct usart_config const *config)
 	if ((uart == UART_EC) && !ec_bridge_enabled_)
 		return;
 #endif  /* BOARD_CR50 */
-	/*
-	 * TODO(b/119329144): Process packet data separately,
-	 * and filter console data based on ccd capability.
-	 * if (ec_comm_is_uart_in_packet_mode(uart))
-	 *	...
-	 */
 
 	while ((count != q_room) && uartn_rx_available(uart)) {
 		uart_in->buffer[tail] = uartn_read_char(uart);