The patch below does not apply to the 5.4-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to stable@vger.kernel.org.

To reproduce the conflict and resubmit, you may use the following commands:

git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-5.4.y git checkout FETCH_HEAD git cherry-pick -x 2a1d728f20edeee7f26dc307ed9df4e0d23947ab # <resolve conflicts, build, test, etc.> git commit -s git send-email --to 'stable@vger.kernel.org' --in-reply-to '2023112235-kettle-curdle-baee@gregkh' --subject-prefix 'PATCH 5.4.y' HEAD^..

Possible dependencies:

2a1d728f20ed ("tty: serial: meson: fix hard LOCKUP on crtscts mode") 5b6806198347 ("serial: meson: Use platform_get_irq() to get the interrupt") 27d44e05d7b8 ("tty: serial: meson: retrieve port FIFO size from DT") 021212f53352 ("serial: meson: remove redundant initialization of variable id") dca3ac8d3bc9 ("tty/serial: Migrate meson_uart to use has_sysrq")

thanks,

greg k-h

------------------ original commit in Linus's tree ------------------

From 2a1d728f20edeee7f26dc307ed9df4e0d23947ab Mon Sep 17 00:00:00 2001 From: Pavel Krasavin pkrasavin@imaqliq.com Date: Sat, 14 Oct 2023 11:39:26 +0000 Subject: [PATCH] tty: serial: meson: fix hard LOCKUP on crtscts mode

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@vger.kernel.org Signed-off-by: Pavel Krasavin pkrasavin@imaqliq.com Reviewed-by: Neil Armstrong neil.armstrong@linaro.org Reviewed-by: Dmitry Rokosov ddrokosov@salutedevices.com

v6: stable tag added v5: https://lore.kernel.org/lkml/OF43DA36FF.2BD3BB21-ON00258A47.005A8125-00258A4... added missed Reviewed-by tags, Fixes tag added according to Dmitry and Neil notes v4: https://lore.kernel.org/lkml/OF55521400.7512350F-ON00258A47.003F7254-00258A4... More correct patch subject according to Jiri's note v3: https://lore.kernel.org/lkml/OF6CF5FFA0.CCFD0E8E-ON00258A46.00549EDF-00258A4... "From:" line added to the mail v2: https://lore.kernel.org/lkml/OF950BEF72.7F425944-ON00258A46.00488A76-00258A4... braces for single statement removed according to Dmitry's note v1: https://lore.kernel.org/lkml/OF28B2B8C9.5BC0CD28-ON00258A46.0037688F-00258A4... Link: https://lore.kernel.org/r/OF66360032.51C36182-ON00258A48.003F656B-00258A48.0...

Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org

diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c index de298bf75d9b..8dd84617e715 100644 --- a/drivers/tty/serial/meson_uart.c +++ b/drivers/tty/serial/meson_uart.c @@ -380,10 +380,14 @@ static void meson_uart_set_termios(struct uart_port *port, 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 +709,7 @@ static int meson_uart_probe(struct platform_device *pdev) 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 +737,7 @@ static int meson_uart_probe(struct platform_device *pdev) 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 +768,8 @@ static int meson_uart_probe(struct platform_device *pdev) 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;