Bloonchipper: USART based transport layer for host command

1. USART host command layer in chip/stm32
2. Fix usart implementation in stm32

BUG=b:147849609
BRANCH=none
TEST=1. make BOARD=bloonchipper -j
     2. usart request and response works on dragonclaw

Change-Id: Idd89d3e490f23aa528ecaf6510c13d16b405de13
Signed-off-by: Bhanu Prakash Maiya <bhanumaiya@google.com>
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2190531
Tested-by: Bhanu Prakash Maiya <bhanumaiya@chromium.org>
Reviewed-by: Jett Rink <jettrink@chromium.org>
Reviewed-by: Tom Hughes <tomhughes@chromium.org>
Reviewed-by: Craig Hesling <hesling@chromium.org>
Commit-Queue: Bhanu Prakash Maiya <bhanumaiya@chromium.org>
Auto-Submit: Bhanu Prakash Maiya <bhanumaiya@chromium.org>

1 files changed, 52 insertions, 0 deletions

diff --git a/chip/stm32/usart_rx_interrupt-stm32f4.c b/chip/stm32/usart_rx_interrupt-stm32f4.c
new file mode 100644
index 0000000000..bfbee469a6
--- /dev/null
+++ b/chip/stm32/usart_rx_interrupt-stm32f4.c
@@ -0,0 +1,52 @@
+/* Copyright 2020 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.
+ */
+
+/* Interrupt based USART RX driver for STM32F0 and STM32F4 */
+
+#include "usart.h"
+
+#include "atomic.h"
+#include "common.h"
+#include "queue.h"
+#include "registers.h"
+
+static void usart_rx_init(struct usart_config const *config)
+{
+	intptr_t base = config->hw->base;
+
+	STM32_USART_CR1(base) |= STM32_USART_CR1_RXNEIE;
+	STM32_USART_CR1(base) |= STM32_USART_CR1_RE;
+#if defined(CHIP_FAMILY_STM32F0) || defined(CHIP_FAMILY_STM32F3) || \
+	defined(CHIP_FAMILY_STM32L4)
+	STM32_USART_CR3(base) |= STM32_USART_CR3_OVRDIS;
+#endif
+}
+
+static void usart_rx_interrupt_handler(struct usart_config const *config)
+{
+	intptr_t base   = config->hw->base;
+	int32_t  status = STM32_USART_SR(base);
+
+	if (status & STM32_USART_SR_RXNE) {
+		uint8_t byte = STM32_USART_RDR(base);
+
+		if (!queue_add_unit(config->producer.queue, &byte))
+			atomic_add(&config->state->rx_dropped, 1);
+	}
+}
+
+struct usart_rx const usart_rx_interrupt = {
+	.producer_ops = {
+		/*
+		 * Nothing to do here, we either had enough space in the queue
+		 * when a character came in or we dropped it already.
+		 */
+		.read = NULL,
+	},
+
+	.init      = usart_rx_init,
+	.interrupt = usart_rx_interrupt_handler,
+	.info      = NULL,
+};