servo_micro: Allow setting the baud rate for usart

We set the baud rate in increments of 100 baud, to avoid
overflowing the 16-bit wValue integer (921600 is the highest we
are likely to use).

Also, increment the buffer size for USART3 to 1024 bytes. That
helps a bit to avoid losing characters, but we still can't keep
up if the host is printing at maximum speed.

BRANCH=servo
BUG=chromium:876651
TEST=baud usart2/3/4 115200 in servo_micro console
TEST=dut-control cpu_uart_baudrate:921600
     seq 1 1000 shows numbers 1 to 226 before buffer overflows

Change-Id: Ifca266189f93def493f207dd29d2cceca4d8d68f
Signed-off-by: Nicolas Boichat <drinkcat@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1189782
Reviewed-by: Nick Sanders <nsanders@chromium.org>

8 files changed, 74 insertions, 13 deletions

diff --git a/board/servo_micro/board.c b/board/servo_micro/board.c
index a665b3dfe8..a06978b84d 100644
--- a/board/servo_micro/board.c
+++ b/board/servo_micro/board.c
@@ -101,7 +101,7 @@ USB_STREAM_CONFIG_USART_IFACE(usart2_usb,
 static struct usart_config const usart3;
 struct usb_stream_config const usart3_usb;
 
-static struct queue const usart3_to_usb = QUEUE_DIRECT(128, uint8_t,
+static struct queue const usart3_to_usb = QUEUE_DIRECT(1024, uint8_t,
 	usart3.producer, usart3_usb.consumer);
 static struct queue const usb_to_usart3 = QUEUE_DIRECT(64, uint8_t,
 	usart3_usb.producer, usart3.consumer);
@@ -203,6 +203,39 @@ DECLARE_CONSOLE_COMMAND(parity, command_uart_parity,
 			"Set parity on uart");
 
 /******************************************************************************
+ * Set baud rate setting on usarts.
+ */
+static int command_uart_baud(int argc, char **argv)
+{
+	int baud = 0;
+	struct usart_config const *usart;
+	char *e;
+
+	if ((argc < 2) || (argc > 3))
+		return EC_ERROR_PARAM_COUNT;
+
+	if (!strcasecmp(argv[1], "usart2"))
+		usart = &usart2;
+	else if (!strcasecmp(argv[1], "usart3"))
+		usart = &usart3;
+	else if (!strcasecmp(argv[1], "usart4"))
+		usart = &usart4;
+	else
+		return EC_ERROR_PARAM1;
+
+	baud = strtoi(argv[2], &e, 0);
+	if (*e || baud < 0)
+		return EC_ERROR_PARAM2;
+
+	usart_set_baud(usart, baud);
+
+	return EC_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(baud, command_uart_baud,
+			"usart[2|3|4] rate",
+			"Set baud rate on uart");
+
+/******************************************************************************
  * Commands for sending the magic non-I2C handshake over I2C bus wires to an
  * ITE IT8320 EC chip to enable direct firmware update (DFU) over I2C mode.
  */
diff --git a/chip/stm32/usart-stm32f0.c b/chip/stm32/usart-stm32f0.c
index 8ae2085498..54d68977ef 100644
--- a/chip/stm32/usart-stm32f0.c
+++ b/chip/stm32/usart-stm32f0.c
@@ -36,11 +36,16 @@ static void usart_variant_enable(struct usart_config const *config)
 	 */
 	configs[config->hw->index] = config;
 
-	usart_set_baud_f0_l(config, clock_get_freq());
+	usart_set_baud(config, config->baud);
 
 	task_enable_irq(config->hw->irq);
 }
 
+void usart_set_baud(struct usart_config const *config, int baud)
+{
+	usart_set_baud_f0_l(config, baud, clock_get_freq());
+}
+
 static void usart_variant_disable(struct usart_config const *config)
 {
 	int index = config->hw->index;
@@ -69,7 +74,8 @@ static void freq_change(void)
 
 	for (i = 0; i < ARRAY_SIZE(configs); ++i)
 		if (configs[i])
-			usart_set_baud_f0_l(configs[i], clock_get_freq());
+			usart_set_baud_f0_l(configs[i], configs[i]->baud,
+					clock_get_freq());
 }
 
 DECLARE_HOOK(HOOK_FREQ_CHANGE, freq_change, HOOK_PRIO_DEFAULT);
diff --git a/chip/stm32/usart-stm32f3.c b/chip/stm32/usart-stm32f3.c
index a6c7fc8991..42a0cf310e 100644
--- a/chip/stm32/usart-stm32f3.c
+++ b/chip/stm32/usart-stm32f3.c
@@ -37,7 +37,7 @@ static void usart_variant_enable(struct usart_config const *config)
 	 */
 	STM32_RCC_CFGR3 |= 0x000f0003;
 
-	usart_set_baud_f0_l(config, 8000000);
+	usart_set_baud_f0_l(config, config->baud, 8000000);
 
 	task_enable_irq(config->hw->irq);
 }
diff --git a/chip/stm32/usart-stm32l.c b/chip/stm32/usart-stm32l.c
index a42eab41ff..f57443cc96 100644
--- a/chip/stm32/usart-stm32l.c
+++ b/chip/stm32/usart-stm32l.c
@@ -39,7 +39,7 @@ static void usart_variant_enable(struct usart_config const *config)
 	 */
 	configs[config->hw->index] = config;
 
-	usart_set_baud_f0_l(config, clock_get_freq());
+	usart_set_baud_f0_l(config, config->baud, clock_get_freq());
 
 	task_enable_irq(config->hw->irq);
 }
@@ -62,7 +62,8 @@ static void freq_change(void)
 
 	for (i = 0; i < ARRAY_SIZE(configs); ++i)
 		if (configs[i])
-			usart_set_baud_f0_l(configs[i], clock_get_freq());
+			usart_set_baud_f0_l(configs[i], configs[i]->baud,
+					clock_get_freq());
 }
 
 DECLARE_HOOK(HOOK_FREQ_CHANGE, freq_change, HOOK_PRIO_DEFAULT);
diff --git a/chip/stm32/usart.c b/chip/stm32/usart.c
index 90be4f6194..0ef357466c 100644
--- a/chip/stm32/usart.c
+++ b/chip/stm32/usart.c
@@ -86,9 +86,10 @@ void usart_shutdown(struct usart_config const *config)
 	config->hw->ops->disable(config);
 }
 
-void usart_set_baud_f0_l(struct usart_config const *config, int frequency_hz)
+void usart_set_baud_f0_l(struct usart_config const *config, int baud,
+			int frequency_hz)
 {
-	int      div  = DIV_ROUND_NEAREST(frequency_hz, config->baud);
+	int      div  = DIV_ROUND_NEAREST(frequency_hz, baud);
 	intptr_t base = config->hw->base;
 
 	if (div / 16 > 0) {
@@ -108,9 +109,10 @@ void usart_set_baud_f0_l(struct usart_config const *config, int frequency_hz)
 	}
 }
 
-void usart_set_baud_f(struct usart_config const *config, int frequency_hz)
+void usart_set_baud_f(struct usart_config const *config, int baud,
+		int frequency_hz)
 {
-	int div = DIV_ROUND_NEAREST(frequency_hz, config->baud);
+	int div = DIV_ROUND_NEAREST(frequency_hz, baud);
 
 	/* STM32F only supports x16 oversampling */
 	STM32_USART_BRR(config->hw->base) = div;
diff --git a/chip/stm32/usart.h b/chip/stm32/usart.h
index d218f64fd5..53b13762e9 100644
--- a/chip/stm32/usart.h
+++ b/chip/stm32/usart.h
@@ -201,8 +201,10 @@ void usart_interrupt(struct usart_config const *config);
  * peripheral variant code uses during initialization and clock frequency
  * change.  The baud rate divisor input frequency is passed in Hertz.
  */
-void usart_set_baud_f0_l(struct usart_config const *config, int frequency_hz);
-void usart_set_baud_f(struct usart_config const *config, int frequency_hz);
+void usart_set_baud_f0_l(struct usart_config const *config, int baud,
+			int frequency_hz);
+void usart_set_baud_f(struct usart_config const *config, int baud,
+		int frequency_hz);
 
 /*
  * Allow specification of parity for this usart.
@@ -217,6 +219,13 @@ void usart_set_parity(struct usart_config const *config, int parity);
 int usart_get_parity(struct usart_config const *config);
 
 /*
+ * Set baud rate for this usart. Note that baud rate will get reset on
+ * core frequency change, so this only makes sense if the board never
+ * goes to deep idle.
+ */
+void usart_set_baud(struct usart_config const *config, int baud);
+
+/*
  * Different families provide different ways of clearing the transmit complete
  * flag.  This function will be provided by the family specific implementation.
  */
diff --git a/chip/stm32/usb-stream.c b/chip/stm32/usb-stream.c
index d66a5ae2a0..79e9e1ace5 100644
--- a/chip/stm32/usb-stream.c
+++ b/chip/stm32/usb-stream.c
@@ -164,9 +164,12 @@ int usb_usart_interface(struct usb_stream_config const *config,
 	case USB_USART_SET_PARITY:
 		usart_set_parity(usart, req.wValue);
 		break;
+	case USB_USART_SET_BAUD:
+		usart_set_baud(usart, req.wValue * 100);
+		break;
 
 	/* TODO(nsanders): support reading parity. */
-	/* TODO(nsanders): support baud. */
+	/* TODO(nsanders): support reading baud. */
 	default:
 		return -1;
 	}
diff --git a/chip/stm32/usb-stream.h b/chip/stm32/usb-stream.h
index f89d62a65c..af96db551d 100644
--- a/chip/stm32/usb-stream.h
+++ b/chip/stm32/usb-stream.h
@@ -277,6 +277,13 @@ enum usb_usart {
 	USB_USART_REQ_BAUD = 2,
 	USB_USART_SET_BAUD = 3,
 };
+
+/*
+ * baud rate is req/set in multiples of 100, to avoid overflowing
+ * 16-bit integer.
+ */
+#define USB_USART_BAUD_MULTIPLIER 100
+
 int usb_usart_interface(struct usb_stream_config const *config,
 		    struct usart_config const *usart,
 		    int interface, usb_uint *rx_buf, usb_uint *tx_buf);