[PATCH] serial: imx: Use uart_port_lock_irqsave() instead of uart_port_lock()

[Xiaolei Wang]

When executing 'ehco mem > /sys/power/state', the following
deadlock occurs. Since there is output during the serial
port entering the suspend process, the suspend will be
interrupted, resulting in the nesting of locks. Therefore,
use uart_port_lock_irqsave instead of uart_port_unlock.

WARNING: inconsistent lock state
6.12.0-rc2-00002-g3c199ed5bd64-dirty #23 Not tainted
--------------------------------
inconsistent {IN-HARDIRQ-W} -> {HARDIRQ-ON-W} usage.
sh/494 [HC0[0]:SC0[0]:HE1:SE1] takes:
c4db5850 (&port_lock_key){?.-.}-{3:3}, at: imx_uart_enable_wakeup+0x14/0x254
{IN-HARDIRQ-W} state was registered at:
  lock_acquire+0x104/0x348
  _raw_spin_lock+0x48/0x84
  imx_uart_int+0x14/0x4dc
  __handle_irq_event_percpu+0xac/0x2fc
  handle_irq_event_percpu+0xc/0x40
  handle_irq_event+0x38/0x8c
  handle_fasteoi_irq+0xb4/0x1b8
  handle_irq_desc+0x1c/0x2c
  gic_handle_irq+0x6c/0xa0
  generic_handle_arch_irq+0x2c/0x64
  call_with_stack+0x18/0x20
  __irq_svc+0x9c/0xbc
  _raw_spin_unlock_irqrestore+0x2c/0x48
  uart_write+0xd8/0x3a0
  do_output_char+0x1a8/0x1e4
  n_tty_write+0x224/0x440
  file_tty_write.constprop.0+0x124/0x250
  do_iter_readv_writev+0x100/0x1e0
  vfs_writev+0xc4/0x448
  do_writev+0x68/0xf8
  ret_fast_syscall+0x0/0x1c
irq event stamp: 31593
hardirqs last  enabled at (31593): [<c1150e48>] _raw_spin_unlock_irqrestore+0x44/0x48
hardirqs last disabled at (31592): [<c07f32f0>] clk_enable_lock+0x60/0x120
softirqs last  enabled at (30334): [<c012d1d4>] handle_softirqs+0x2cc/0x478
softirqs last disabled at (30325): [<c012d510>] __irq_exit_rcu+0x120/0x15c

other info that might help us debug this:
 Possible unsafe locking scenario:

       CPU0
       ----
  lock(&port_lock_key);
  <Interrupt>
    lock(&port_lock_key);

Fixes: 3c199ed5bd64 ("serial: imx: Grab port lock in imx_uart_enable_wakeup()")
Signed-off-by: Xiaolei Wang <xiaolei.wang at windriver.com>
---
 drivers/tty/serial/imx.c | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 17f70e4bee43..4470bcb3ef19 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2691,8 +2691,9 @@ static void imx_uart_save_context(struct imx_port *sport)
 static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
 {
 	u32 ucr3;
+	unsigned long flags;
 
-	uart_port_lock(&sport->port);
+	uart_port_lock_irqsave(&sport->port, &flags);
 
 	ucr3 = imx_uart_readl(sport, UCR3);
 	if (on) {
@@ -2714,7 +2715,7 @@ static void imx_uart_enable_wakeup(struct imx_port *sport, bool on)
 		imx_uart_writel(sport, ucr1, UCR1);
 	}
 
-	uart_port_unlock(&sport->port);
+	uart_port_unlock_irqrestore(&sport->port, flags);
 }
 
 static int imx_uart_suspend_noirq(struct device *dev)
-- 
2.25.1