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refactor(st-uart): compute the over sampling dynamically

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The parameter over_sampling of stm32_uart_init_s is not required
as it can be computed dynamically from clock rate of the serial
device and the requested baudrate.

Oversampling by 8 is allowed only for higher speed
(up to clock_rate / 8) to reduce the maximum receiver tolerance
to clock deviation.

This patch update the driver, the serial init struct and the
only user, the stm32cubeprogrammer over uart support.

Change-Id: I422731089730a288defeb7fa49886db65d0902b2
Signed-off-by: Patrick Delaunay <patrick.delaunay@foss.st.com>
This commit is contained in:
Patrick Delaunay 2022-03-02 15:29:08 +01:00 • committed by Yann Gautier
parent 278bc857d8
commit 1258189515
3 changed files with 31 additions and 38 deletions
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53
drivers/st/uart/stm32_uart.c
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, STMicroelectronics - All Rights Reserved
* Copyright (c) 2021-2022, STMicroelectronics - All Rights Reserved
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@ -106,7 +106,33 @@ static int uart_set_config(struct stm32_uart_handle_s *huart,
{
uint32_t tmpreg;
unsigned long clockfreq;
unsigned long int_div;
uint32_t brrtemp;
uint32_t over_sampling;
/*---------------------- USART BRR configuration --------------------*/
clockfreq = uart_get_clock_freq(huart);
if (clockfreq == 0UL) {
return -ENODEV;
}
int_div = clockfreq / init->baud_rate;
if (int_div < 16U) {
uint32_t usartdiv = uart_div_sampling8(clockfreq,
init->baud_rate,
init->prescaler);
brrtemp = (usartdiv & USART_BRR_DIV_MANTISSA) |
((usartdiv & USART_BRR_DIV_FRACTION) >> 1);
over_sampling = USART_CR1_OVER8;
} else {
brrtemp = uart_div_sampling16(clockfreq,
init->baud_rate,
init->prescaler) &
(USART_BRR_DIV_FRACTION | USART_BRR_DIV_MANTISSA);
over_sampling = 0x0U;
}
mmio_write_32(huart->base + USART_BRR, brrtemp);
/*
* ---------------------- USART CR1 Configuration --------------------
@ -115,12 +141,12 @@ static int uart_set_config(struct stm32_uart_handle_s *huart,
* - set the M bits according to init->word_length value,
* - set PCE and PS bits according to init->parity value,
* - set TE and RE bits according to init->mode value,
* - set OVER8 bit according to init->over_sampling value.
* - set OVER8 bit according baudrate and clock.
*/
tmpreg = init->word_length |
init->parity |
init->mode |
init->over_sampling |
over_sampling |
init->fifo_mode;
mmio_clrsetbits_32(huart->base + USART_CR1, STM32_UART_CR1_FIELDS, tmpreg);
@ -161,27 +187,6 @@ static int uart_set_config(struct stm32_uart_handle_s *huart,
mmio_clrsetbits_32(huart->base + USART_PRESC, USART_PRESC_PRESCALER,
init->prescaler);
/*---------------------- USART BRR configuration --------------------*/
clockfreq = uart_get_clock_freq(huart);
if (clockfreq == 0UL) {
return -ENODEV;
}
if (init->over_sampling == STM32_UART_OVERSAMPLING_8) {
uint32_t usartdiv = uart_div_sampling8(clockfreq,
init->baud_rate,
init->prescaler);
brrtemp = (usartdiv & USART_BRR_DIV_MANTISSA) |
((usartdiv & USART_BRR_DIV_FRACTION) >> 1);
} else {
brrtemp = uart_div_sampling16(clockfreq,
init->baud_rate,
init->prescaler) &
(USART_BRR_DIV_FRACTION | USART_BRR_DIV_MANTISSA);
}
mmio_write_32(huart->base + USART_BRR, brrtemp);
return 0;
}

13
include/drivers/st/stm32_uart.h
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, STMicroelectronics - All Rights Reserved
* Copyright (c) 2021-2022, STMicroelectronics - All Rights Reserved
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@ -34,10 +34,6 @@
#define STM32_UART_HWCONTROL_CTS USART_CR3_CTSE
#define STM32_UART_HWCONTROL_RTS_CTS (USART_CR3_RTSE | USART_CR3_CTSE)
/* UART over sampling */
#define STM32_UART_OVERSAMPLING_16 0x00000000U
#define STM32_UART_OVERSAMPLING_8 USART_CR1_OVER8
/* UART prescaler */
#define STM32_UART_PRESCALER_DIV1 0x00000000U
#define STM32_UART_PRESCALER_DIV2 0x00000001U
@ -112,13 +108,6 @@ struct stm32_uart_init_s {
* value of @ref STM32_UARTHWCONTROL_*.
*/
uint32_t over_sampling; /*
* Specifies whether the over sampling
* 8 is enabled or disabled.
* This parameter can be a value of
* @ref STM32_UART_OVERSAMPLING_*.
*/
uint32_t one_bit_sampling; /*
* Specifies whether a single sample
* or three samples' majority vote is

3
plat/st/common/stm32cubeprogrammer_uart.c
View file

@ -1,5 +1,5 @@
/*
* Copyright (c) 2021, STMicroelectronics - All Rights Reserved
* Copyright (c) 2021-2022, STMicroelectronics - All Rights Reserved
*
* SPDX-License-Identifier: BSD-3-Clause
*/
@ -492,7 +492,6 @@ const struct stm32_uart_init_s init = {
.parity = STM32_UART_PARITY_EVEN,
.hw_flow_control = STM32_UART_HWCONTROL_NONE,
.mode = STM32_UART_MODE_TX_RX,
.over_sampling = STM32_UART_OVERSAMPLING_16,
.fifo_mode = STM32_UART_FIFOMODE_EN,
};