Subject: patch "serial: stm32: fix clearing interrupt error flags" added to tty-testing
To:     fabrice.gasnier@st.com, gregkh@linuxfoundation.org,
        stable@vger.kernel.org
From:   <gregkh@linuxfoundation.org>
Date:   Thu, 21 Nov 2019 18:23:30 +0100
Message-ID: <1574357010225218@kroah.com>
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This is a note to let you know that I've just added the patch titled

    serial: stm32: fix clearing interrupt error flags

to my tty git tree which can be found at
    git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty.git
in the tty-testing branch.

The patch will show up in the next release of the linux-next tree
(usually sometime within the next 24 hours during the week.)

The patch will be merged to the tty-next branch sometime soon,
after it passes testing, and the merge window is open.

If you have any questions about this process, please let me know.


From 1250ed7114a977cdc2a67a0c09d6cdda63970eb9 Mon Sep 17 00:00:00 2001
From: Fabrice Gasnier <fabrice.gasnier@st.com>
Date: Thu, 21 Nov 2019 09:10:49 +0100
Subject: 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: 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>
---
 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 df90747ee3a8..2f72514d63ed 100644
--- a/drivers/tty/serial/stm32-usart.c
+++ b/drivers/tty/serial/stm32-usart.c
@@ -240,8 +240,8 @@ 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++;
@@ -435,7 +435,7 @@ 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);
-- 
2.24.0