[PATCH 04/13] serial: linflexuart: Correctly clear UARTSR in buffer mode

[Larisa Grigore]

The TX interrupt handler should not clear RX-related fields in UARTSR,
and vice versa.
The handler checks UARTSR.DRFRFE before invoking linflex_rxint, and
UARTSR.DTFTFF before invoking linflex_txint.
Incorrectly clearing these bits may cause the interrupt handler to miss
characters.
Same applies to linflex_console_putchar which should clear only
UARTSR.DTFTFF.

Fixes: 09864c1cdf5c ("tty: serial: Add linflexuart driver for S32V234")
Signed-off-by: Larisa Grigore <larisa.grig...@oss.nxp.com>
---
 drivers/tty/serial/fsl_linflexuart.c | 9 ++++-----
 1 file changed, 4 insertions(+), 5 deletions(-)

diff --git a/drivers/tty/serial/fsl_linflexuart.c 
b/drivers/tty/serial/fsl_linflexuart.c
index 9111e7af62ea..a48240b0a5f2 100644
--- a/drivers/tty/serial/fsl_linflexuart.c
+++ b/drivers/tty/serial/fsl_linflexuart.c
@@ -169,7 +169,7 @@ static void linflex_put_char(struct uart_port *sport, 
unsigned char c)
                                LINFLEXD_UARTSR_DTFTFF)
                ;
 
-       writel(status | LINFLEXD_UARTSR_DTFTFF, sport->membase + UARTSR);
+       writel(LINFLEXD_UARTSR_DTFTFF, sport->membase + UARTSR);
 }
 
 static inline void linflex_transmit_buffer(struct uart_port *sport)
@@ -255,7 +255,8 @@ static irqreturn_t linflex_rxint(int irq, void *dev_id)
                                sport->icount.parity++;
                }
 
-               writel(status, sport->membase + UARTSR);
+
+               writel(~(u32)LINFLEXD_UARTSR_DTFTFF, sport->membase + UARTSR);
                status = readl(sport->membase + UARTSR);
 
                if (brk) {
@@ -573,9 +574,7 @@ static void linflex_console_putchar(struct uart_port *port, 
unsigned char ch)
                                != LINFLEXD_UARTSR_DTFTFF)
                        ;
 
-               writel((readl(port->membase + UARTSR) |
-                                       LINFLEXD_UARTSR_DTFTFF),
-                                       port->membase + UARTSR);
+               writel(LINFLEXD_UARTSR_DTFTFF, port->membase + UARTSR);
        }
 }
 
-- 
2.47.0