6.5-stable review patch. If anyone has any objections, please let me know.
------------------
From: Pavel Krasavin <pkrasavin@xxxxxxxxxxx>
commit 2a1d728f20edeee7f26dc307ed9df4e0d23947ab upstream.
There might be hard lockup if we set crtscts mode on port without RTS/CTS configured:
# stty -F /dev/ttyAML6 crtscts; echo 1 > /dev/ttyAML6; echo 2 > /dev/ttyAML6
[ 95.890386] rcu: INFO: rcu_preempt detected stalls on CPUs/tasks:
[ 95.890857] rcu: 3-...0: (201 ticks this GP) idle=e33c/1/0x4000000000000000 softirq=5844/5846 fqs=4984
[ 95.900212] rcu: (detected by 2, t=21016 jiffies, g=7753, q=296 ncpus=4)
[ 95.906972] Task dump for CPU 3:
[ 95.910178] task:bash state:R running task stack:0 pid:205 ppid:1 flags:0x00000202
[ 95.920059] Call trace:
[ 95.922485] __switch_to+0xe4/0x168
[ 95.925951] 0xffffff8003477508
[ 95.974379] watchdog: Watchdog detected hard LOCKUP on cpu 3
[ 95.974424] Modules linked in: 88x2cs(O) rtc_meson_vrtc
Possible solution would be to not allow to setup crtscts on such port.
Tested on S905X3 based board.
Fixes: ff7693d079e5 ("ARM: meson: serial: add MesonX SoC on-chip uart driver")
Cc: stable@xxxxxxxxxxxxxxx
Signed-off-by: Pavel Krasavin <pkrasavin@xxxxxxxxxxx>
Reviewed-by: Neil Armstrong <neil.armstrong@xxxxxxxxxx>
Reviewed-by: Dmitry Rokosov <ddrokosov@xxxxxxxxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
drivers/tty/serial/meson_uart.c | 14 +++++++++++---
1 file changed, 11 insertions(+), 3 deletions(-)
--- a/drivers/tty/serial/meson_uart.c
+++ b/drivers/tty/serial/meson_uart.c
@@ -379,10 +379,14 @@ static void meson_uart_set_termios(struc
else
val |= AML_UART_STOP_BIT_1SB;
- if (cflags & CRTSCTS)
- val &= ~AML_UART_TWO_WIRE_EN;
- else
+ if (cflags & CRTSCTS) {
+ if (port->flags & UPF_HARD_FLOW)
+ val &= ~AML_UART_TWO_WIRE_EN;
+ else
+ termios->c_cflag &= ~CRTSCTS;
+ } else {
val |= AML_UART_TWO_WIRE_EN;
+ }
writel(val, port->membase + AML_UART_CONTROL);
@@ -697,6 +701,7 @@ static int meson_uart_probe(struct platf
u32 fifosize = 64; /* Default is 64, 128 for EE UART_0 */
int ret = 0;
int irq;
+ bool has_rtscts;
if (pdev->dev.of_node)
pdev->id = of_alias_get_id(pdev->dev.of_node, "serial");
@@ -724,6 +729,7 @@ static int meson_uart_probe(struct platf
return irq;
of_property_read_u32(pdev->dev.of_node, "fifo-size", &fifosize);
+ has_rtscts = of_property_read_bool(pdev->dev.of_node, "uart-has-rtscts");
if (meson_ports[pdev->id]) {
dev_err(&pdev->dev, "port %d already allocated\n", pdev->id);
@@ -743,6 +749,8 @@ static int meson_uart_probe(struct platf
port->mapsize = resource_size(res_mem);
port->irq = irq;
port->flags = UPF_BOOT_AUTOCONF | UPF_LOW_LATENCY;
+ if (has_rtscts)
+ port->flags |= UPF_HARD_FLOW;
port->has_sysrq = IS_ENABLED(CONFIG_SERIAL_MESON_CONSOLE);
port->dev = &pdev->dev;
port->line = pdev->id;
