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/* Copyright 2015 The ChromiumOS Authors
* 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 STM32L */
#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;
}
static void usart_rx_interrupt_handler(struct usart_config const *config)
{
intptr_t base = config->hw->base;
int32_t status = STM32_USART_SR(base);
/*
* We have to check and clear the overrun error flag on STM32L because
* we can't disable it.
*/
if (status & STM32_USART_SR_ORE) {
#ifdef STM32_USART_ICR_ORECF
/*
* Newer series (STM32L4xx and STM32L5xx) have an explicit
* "interrupt clear" register.
*
* ST reference code does blind write to this register, as is
* usual with the "write 1 to clear" convention, despite the
* datasheet listing the bits as "keep at reset value", (which
* we assume is due to copying from the description of
* reserved bits in read/write registers.)
*/
STM32_USART_ICR(config->hw->base) = STM32_USART_ICR_ORECF;
#else
/*
* On the older series STM32L1xx, the overrun bit is cleared
* by a read of the status register, followed by a read of the
* data register.
*
* In the unlikely event that the overrun error bit was set but
* the RXNE bit was not (possibly because a read was done from
* RDR without first reading the status register) we do a read
* here to clear the overrun error bit.
*/
if (!(status & STM32_USART_SR_RXNE))
(void)STM32_USART_RDR(config->hw->base);
#endif
atomic_add((atomic_t *)&(config->state->rx_overrun), 1);
}
if (status & STM32_USART_SR_RXNE) {
uint8_t byte = STM32_USART_RDR(base);
if (!queue_add_unit(config->producer.queue, &byte))
atomic_add((atomic_t *)&(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,
};
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