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serial: stm32: fix clearing interrupt error flags 

The interrupt clear flag register is a "write 1 to clear" register.
So, only writing ones allows to clear flags:
- Replace buggy stm32_clr_bits() by a simple write to clear error flags
- Replace useless read/modify/write stm32_set_bits() routine by a
  simple write to clear TC (transfer complete) flag.

Fixes: 4f01d833fd ("serial: stm32: fix rx error handling")
Signed-off-by: Fabrice Gasnier <fabrice.gasnier@st.com>
Cc: stable <stable@vger.kernel.org>
Link: https://lore.kernel.org/r/1574323849-1909-1-git-send-email-fabrice.gasnier@st.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Fabrice Gasnier 2019-11-21 09:10:49 +01:00 committed by Greg Kroah-Hartman
parent da88ac0bd6
commit 1250ed7114
1 changed files with 3 additions and 3 deletions
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6
drivers/tty/serial/stm32-usart.c
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@ -240,8 +240,8 @@ static void stm32_receive_chars(struct uart_port *port, bool threaded)
* cleared by the sequence [read SR - read DR]. * cleared by the sequence [read SR - read DR].
*/ */
if ((sr & USART_SR_ERR_MASK) && ofs->icr != UNDEF_REG) if ((sr & USART_SR_ERR_MASK) && ofs->icr != UNDEF_REG)
stm32_clr_bits(port, ofs->icr, USART_ICR_ORECF | writel_relaxed(sr & USART_SR_ERR_MASK,
USART_ICR_PECF | USART_ICR_FECF); port->membase + ofs->icr);
c = stm32_get_char(port, &sr, &stm32_port->last_res); c = stm32_get_char(port, &sr, &stm32_port->last_res);
port->icount.rx++; port->icount.rx++;
@ -435,7 +435,7 @@ static void stm32_transmit_chars(struct uart_port *port)
if (ofs->icr == UNDEF_REG) if (ofs->icr == UNDEF_REG)
stm32_clr_bits(port, ofs->isr, USART_SR_TC); stm32_clr_bits(port, ofs->isr, USART_SR_TC);
else else
stm32_set_bits(port, ofs->icr, USART_ICR_TCCF); writel_relaxed(USART_ICR_TCCF, port->membase + ofs->icr);
if (stm32_port->tx_ch) if (stm32_port->tx_ch)
stm32_transmit_chars_dma(port); stm32_transmit_chars_dma(port);