I believe it would be necessary to include a 'Fixes' tag for that. Neil, what do you think? Since a HARDLOCKUP is an undesirable situation, I don't think we want to have it in the LTS kernels either. On Fri, Oct 13, 2023 at 11:48:39AM +0000, Pavel Krasavin wrote: > From: Pavel Krasavin <pkrasavin@xxxxxxxxxxx> > > 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 <pkrasavin@xxxxxxxxxxx> > --- > v4: More correct patch subject according to Jiri's note > v3: https://lore.kernel.org/lkml/OF6CF5FFA0.CCFD0E8E-ON00258A46.00549EDF-00258A46.0054BB62@xxxxxx/ > "From:" line added to the mail > v2: https://lore.kernel.org/lkml/OF950BEF72.7F425944-ON00258A46.00488A76-00258A46.00497D44@xxxxxx/ > braces for single statement removed according to Dmitry's note > v1: https://lore.kernel.org/lkml/OF28B2B8C9.5BC0CD28-ON00258A46.0037688F-00258A46.0039155B@xxxxxx/ > --- > > --- a/drivers/tty/serial/meson_uart.c 2023-10-12 15:44:02.410538523 +0300 > +++ b/drivers/tty/serial/meson_uart.c 2023-10-12 15:58:06.242395253 +0300 > @@ -380,10 +380,14 @@ 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); > > @@ -705,6 +709,7 @@ 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 +737,7 @@ 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 +768,8 @@ 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 > linux-amlogic@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-amlogic -- Thank you, Dmitry
