[PATCH AUTOSEL 4.14 371/371] serial: stm32: fix clearing interrupt error flags

Sasha Levin
2020-01-16T17:31:29Z

From: Fabrice Gasnier <fabrice.gasnier@st.com>

[ Upstream commit 1250ed7114a977cdc2a67a0c09d6cdda63970eb9 ]

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: 4f01d833fdcd ("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>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
drivers/tty/serial/stm32-usart.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/drivers/tty/serial/stm32-usart.c b/drivers/tty/serial/stm32-usart.c
index f8f3f8fafd9f..1e854e1851fb 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -132,8 +132,8 @@ static void stm32_receive_chars(struct uart_port *port, bool threaded)
* cleared by the sequence [read SR - read DR].
*/
if ((sr & USART_SR_ERR_MASK) && ofs->icr != UNDEF_REG)
- stm32_clr_bits(port, ofs->icr, USART_ICR_ORECF |
- USART_ICR_PECF | USART_ICR_FECF);
+ writel_relaxed(sr & USART_SR_ERR_MASK,
+ port->membase + ofs->icr);

c = stm32_get_char(port, &sr, &stm32_port->last_res);
port->icount.rx++;
@@ -302,7 +302,7 @@ static void stm32_transmit_chars(struct uart_port *port)
if (ofs->icr == UNDEF_REG)
stm32_clr_bits(port, ofs->isr, USART_SR_TC);
else
- stm32_set_bits(port, ofs->icr, USART_ICR_TCCF);
+ writel_relaxed(USART_ICR_TCCF, port->membase + ofs->icr);

if (stm32_port->tx_ch)
stm32_transmit_chars_dma(port);
--
2.20.1