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.
Signed-off-by: Pavel Krasavin <[email protected]>
--- a/drivers/tty/serial/meson_uart.c 2023-08-22 12:46:50.933814528 +0300
+++ b/drivers/tty/serial/meson_uart.c 2023-08-22 14:48:15.593169948 +0300
@@ -380,10 +380,15 @@ 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);
@@ -705,6 +710,7 @@ 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");
@@ -732,6 +738,7 @@ 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]) {
return dev_err_probe(&pdev->dev, -EBUSY,
@@ -762,6 +769,8 @@ 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;
Hello Pavel,
On Thu, Oct 12, 2023 at 10:23:30AM +0000, [email protected] wrote:
> 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.
>
> Signed-off-by: Pavel Krasavin <[email protected]>
>
> --- a/drivers/tty/serial/meson_uart.c 2023-08-22 12:46:50.933814528 +0300
> +++ b/drivers/tty/serial/meson_uart.c 2023-08-22 14:48:15.593169948 +0300
> @@ -380,10 +380,15 @@ 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;
> + }
Please do not use braces where is single statement. In other words:
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;
}
> + } else {
> val |= AML_UART_TWO_WIRE_EN;
> + }
>
> writel(val, port->membase + AML_UART_CONTROL);
>
> @@ -705,6 +710,7 @@ 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");
> @@ -732,6 +738,7 @@ 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]) {
> return dev_err_probe(&pdev->dev, -EBUSY,
> @@ -762,6 +769,8 @@ 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;
>
> _______________________________________________
> linux-amlogic mailing list
> [email protected]
> http://lists.infradead.org/mailman/listinfo/linux-amlogic
--
Thank you,
Dmitry
Hello Dmitry,
----- "Dmitry Rokosov" <[email protected]> писал(а): -----
> Please do not use braces where is single statement. In other words:
>
> 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;
> }
thank you for your note, I will provide v2 without braces.
--
Regards,
Pavel.