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serial: stm32: fix TX and RX FIFO thresholds

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TX and RX FIFO thresholds may be cleared after suspend/resume, depending
on the low power mode.

Those configurations (done in startup) are not effective for UART console,
as:
- the reference manual indicates that FIFOEN bit can only be written when
  the USART is disabled (UE=0)
- a set_termios (where UE is set) is requested firstly for console
  enabling, before the startup.

Fixes: 84872dc448 ("serial: stm32: add RX and TX FIFO flush")
Signed-off-by: Erwan Le Ray <erwan.leray@foss.st.com>
Link: https://lore.kernel.org/r/20210304162308.8984-5-erwan.leray@foss.st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Erwan Le Ray 2021-03-04 17:22:59 +01:00 committed by Greg Kroah-Hartman
parent f264c6f6ae
commit 25a8e7611d
1 changed files with 9 additions and 14 deletions
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23
drivers/tty/serial/stm32-usart.c
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@ -649,19 +649,8 @@ static int stm32_usart_startup(struct uart_port *port)
if (ofs->rqr != UNDEF_REG)
stm32_usart_set_bits(port, ofs->rqr, USART_RQR_RXFRQ);
/* Tx and RX FIFO configuration */
if (stm32_port->fifoen) {
val = readl_relaxed(port->membase + ofs->cr3);
val &= ~(USART_CR3_TXFTCFG_MASK | USART_CR3_RXFTCFG_MASK);
val |= USART_CR3_TXFTCFG_HALF << USART_CR3_TXFTCFG_SHIFT;
val |= USART_CR3_RXFTCFG_HALF << USART_CR3_RXFTCFG_SHIFT;
writel_relaxed(val, port->membase + ofs->cr3);
}
/* RX FIFO enabling */
/* RX enabling */
val = stm32_port->cr1_irq | USART_CR1_RE | BIT(cfg->uart_enable_bit);
if (stm32_port->fifoen)
val |= USART_CR1_FIFOEN;
stm32_usart_set_bits(port, ofs->cr1, val);
return 0;
@ -770,9 +759,15 @@ static void stm32_usart_set_termios(struct uart_port *port,
if (stm32_port->fifoen)
cr1 |= USART_CR1_FIFOEN;
cr2 = 0;
/* Tx and RX FIFO configuration */
cr3 = readl_relaxed(port->membase + ofs->cr3);
cr3 &= USART_CR3_TXFTIE | USART_CR3_RXFTCFG_MASK | USART_CR3_RXFTIE
| USART_CR3_TXFTCFG_MASK;
cr3 &= USART_CR3_TXFTIE | USART_CR3_RXFTIE;
if (stm32_port->fifoen) {
cr3 &= ~(USART_CR3_TXFTCFG_MASK | USART_CR3_RXFTCFG_MASK);
cr3 |= USART_CR3_TXFTCFG_HALF << USART_CR3_TXFTCFG_SHIFT;
cr3 |= USART_CR3_RXFTCFG_HALF << USART_CR3_RXFTCFG_SHIFT;
}
if (cflag & CSTOPB)
cr2 |= USART_CR2_STOP_2B;