control EC USB-UART bridge

This CL separates the control on USB-UART bridge of EC device from
EC UART control. USB-UART bridge shall be enabled if CCD connection
is detected and the CCD capability is enabled. Otherwise, EC USB-UART
shall be disabled. By doing so, CCD capability can be observed even
when EC-CR50 communication enables EC UART.

This patch increases the flash usage by 204 bytes

BUG=b:148247228
BRANCH=cr50, cr50_mp
TEST=ran firmware_Cr50CCDServoCap on Helios.

> ccd
State: Locked
Password: none
Flags: 0x000001
Capabilities: 0000000000000000
...
> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   connected
CCD EXT: enabled
State flags: UARTAP UARTEC I2C USBEC

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   disconnected
CCD EXT: enabled
State flags: UARTAP+TX UARTEC USBEC
CCD ports blocked: (none)

> ccd
State: Opened
Password: none
Flags: 0x800001
Capabilities: 5555454115000000
...
> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   connected
CCD EXT: enabled
State flags: UARTAP UARTEC I2C USBEC+TX
CCD ports blocked: (none)

> ccdstate
AP:      on
AP UART: on
EC:      on
Rdd:     connected
Servo:   undetectable
CCD EXT: enabled
State flags: UARTAP+TX UARTEC+TX I2C SPI USBEC+TX
CCD ports blocked: (none)

Change-Id: I6bb560a05831105ff68a9e13e4b28b002ed98096
Signed-off-by: Namyoon Woo <namyoon@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2018061
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>
Reviewed-by: Mary Ruthven <mruthven@chromium.org>

2 files changed, 62 insertions, 7 deletions

diff --git a/chip/g/usart.c b/chip/g/usart.c
index d7ca39ea14..68ab726814 100644
--- a/chip/g/usart.c
+++ b/chip/g/usart.c
@@ -129,19 +129,57 @@ USB_STREAM_CONFIG(ec_usb,
 		  ec_uart_to_usb)
 #endif
 
+#ifdef BOARD_CR50
+static uint8_t ec_bridge_enabled_;
+static uint8_t ec_bridge_tx_enabled_;
+
+void uart_ec_bridge_enable(int enable, int write)
+{
+	write = enable && write;
+
+	if (write && !ec_bridge_tx_enabled_)
+		task_trigger_irq(GC_IRQNUM_UART2_TXINT);
+
+	ec_bridge_enabled_ = enable;
+	ec_bridge_tx_enabled_ = write;
+}
+
+int uart_ec_bridge_is_enabled(void)
+{
+	return !!ec_bridge_enabled_;
+}
+
+int uart_ec_bridge_tx_is_enabled(void)
+{
+	return !!ec_bridge_tx_enabled_;
+}
+
+#endif  /* BOARD_CR50 */
+
 void get_data_from_usb(struct usart_config const *config)
 {
 	struct queue const *uart_out = config->consumer.queue;
 	int c;
 
 #ifdef BOARD_CR50
-	/*
-	 * If EC-CR50 communication is on-going, then let's not forward
-	 * console input to EC for now.
-	 */
-	if (ec_comm_is_uart_in_packet_mode(config->uart))
-		return;
-#endif
+	if (config->uart == UART_EC) {
+		/*
+		 * If USB-to-UART bridging is disabled, drop all input data.
+		 * Otherwise, data could be pushed into UART TX FIFO, and
+		 * transferred to EC eventually once EC-CR50 communication
+		 * enables EC UART.
+		 */
+		if (!ec_bridge_tx_enabled_)
+			return;
+
+		/*
+		 * If EC-CR50 communication is on-going, then let's not forward
+		 * console input to EC for now.
+		 */
+		if (ec_comm_is_uart_in_packet_mode(UART_EC))
+			return;
+	}
+#endif  /* BOARD_CR50 */
 
 	/* Copy output from buffer until TX fifo full or output buffer empty */
 	while (queue_count(uart_out) && QUEUE_REMOVE_UNITS(uart_out, &c, 1))
@@ -170,6 +208,14 @@ void send_data_to_usb(struct usart_config const *config)
 	tail = uart_in->state->tail & mask;
 	count = 0;
 
+#ifdef BOARD_CR50
+	/*
+	 * If UART-to-USB bridging is not allowed, do not put any output
+	 * data to uart_in queue.
+	 */
+	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.
diff --git a/chip/g/usart.h b/chip/g/usart.h
index cd3a9cfe40..2d9f04974f 100644
--- a/chip/g/usart.h
+++ b/chip/g/usart.h
@@ -74,4 +74,13 @@ void get_data_from_usb(struct usart_config const *config);
 /* Helper for UART bitbang mode. */
 extern struct usart_config const ec_uart;
 
+/* Change EC UART-USB Bridge status */
+void uart_ec_bridge_enable(int enabled, int write);
+
+/* Return non-zero if EC UART-USB Bridge is enabled, or 0 otherwise */
+int uart_ec_bridge_is_enabled(void);
+
+/* Return non-zero if EC UART-USB Bridge is readwritable, or 0 otherwise */
+int uart_ec_bridge_tx_is_enabled(void);
+
 #endif  /* __CROS_FORWARD_UART_H */