tty: serial: linflexuart: Fix magic SysRq handling

Following an incorrect indentation reported to me by Dan Carpenter, I
noticed that the SysRq lines were inherited from the lpuart driver[1] (note
how the 'continue' is aligned to 'sport->port.sysrq = 0') and we have never
actually tested the SysRq support.

'sport->sysrq = 0' is not necessary neither before nor after 'continue',
because sysrq will already be 0 after uart_handle_sysrq_char() will finish.
Also, since the LINFlexD driver never called uart_handle_break(), sysrq
would have never been set to a nonzero value, so uart_handle_sysrq_char()
was not going to do anything.

Break conditions are detected based on a null data byte along with a
framing error (stop bit sampled to 0).

[1] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/tree/drivers/tty/serial/fsl_lpuart.c?h=b3e3bf2ef2c74f5ce5c19510edbbb9bfc1d249c2#n659

Fixes: 09864c1cdf5c ("tty: serial: Add linflexuart driver for S32V234")
Signed-off-by: Stefan-Gabriel Mirea <stefan-gabriel.mirea@nxp.com>
Reported-by: kbuild test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@oracle.com>
Link: https://lore.kernel.org/r/20190918184439.7465-1-stefan-gabriel.mirea@nxp.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/tty/serial/fsl_linflexuart.c b/drivers/tty/serial/fsl_linflexuart.c
index 68d74f2b5106ac5455993bd2a8201219e515b8fc..a32f0d2afd596ba4d1f6ebe08f799c5e31dec80c 100644 (file)
--- a/drivers/tty/serial/fsl_linflexuart.c
+++ b/drivers/tty/serial/fsl_linflexuart.c
@@ -3,7 +3,7 @@
  * Freescale linflexuart serial port driver
  *
  * Copyright 2012-2016 Freescale Semiconductor, Inc.
- * Copyright 2017-2018 NXP
+ * Copyright 2017-2019 NXP
  */
 
 #if defined(CONFIG_SERIAL_FSL_LINFLEXUART_CONSOLE) && \
@@ -246,12 +246,14 @@ static irqreturn_t linflex_rxint(int irq, void *dev_id)
        struct tty_port *port = &sport->state->port;
        unsigned long flags, status;
        unsigned char rx;
+       bool brk;
 
        spin_lock_irqsave(&sport->lock, flags);
 
        status = readl(sport->membase + UARTSR);
        while (status & LINFLEXD_UARTSR_RMB) {
                rx = readb(sport->membase + BDRM);
+               brk = false;
                flg = TTY_NORMAL;
                sport->icount.rx++;
 
@@ -261,8 +263,11 @@ static irqreturn_t linflex_rxint(int irq, void *dev_id)
                                status |= LINFLEXD_UARTSR_SZF;
                        if (status & LINFLEXD_UARTSR_BOF)
                                status |= LINFLEXD_UARTSR_BOF;
-                       if (status & LINFLEXD_UARTSR_FEF)
+                       if (status & LINFLEXD_UARTSR_FEF) {
+                               if (!rx)
+                                       brk = true;
                                status |= LINFLEXD_UARTSR_FEF;
+                       }
                        if (status & LINFLEXD_UARTSR_PE)
                                status |=  LINFLEXD_UARTSR_PE;
                }
@@ -271,13 +276,15 @@ static irqreturn_t linflex_rxint(int irq, void *dev_id)
                       sport->membase + UARTSR);
                status = readl(sport->membase + UARTSR);
 
-               if (uart_handle_sysrq_char(sport, (unsigned char)rx))
-                       continue;
-
+               if (brk) {
+                       uart_handle_break(sport);
+               } else {
 #ifdef SUPPORT_SYSRQ
-                       sport->sysrq = 0;
+                       if (uart_handle_sysrq_char(sport, (unsigned char)rx))
+                               continue;
 #endif
-               tty_insert_flip_char(port, rx, flg);
+                       tty_insert_flip_char(port, rx, flg);
+               }
        }
 
        spin_unlock_irqrestore(&sport->lock, flags);