On 2020-07-05 12:22, Andy Shevchenko wrote:
On Sun, Jul 05, 2020 at 11:28:56AM +0100, Marc Zyngier wrote:
On 2020-07-05 11:07, Andy Shevchenko wrote:
> On Sun, Jul 5, 2020 at 12:32 PM Marc Zyngier <maz@xxxxxxxxxx> wrote:
> >
> > The meson UART driver triggers a lockdep splat at boot time, due
> > to the new expectation that the driver has to initialize the
> > per-port spinlock itself.
> >
> > It remains unclear why a double initialization of the port
> > spinlock is a desirable outcome, but in the meantime let's
> > fix the splat.
> >
>
> Thanks!
>
> Can you test patch from [1] if it helps and doesn't break anything in
> your case?
>
> [1]:
> https://lore.kernel.org/linux-serial/20200217114016.49856-1-andriy.shevchenko@xxxxxxxxxxxxxxx/T/#m9255e2a7474b160e66c7060fca5323ca3df49cfd
On its own, this patch doesn't seem to cure the issue (and it
adds a compile-time warning due to unused flags).
Ah, sorry, I didn't compile it.
And after second though I think we simple need to initialise spin lock
there.
Can you try below (compile-tested only):
From ed4c882e7dc3fdfcea706ada0678c060c36163b3 Mon Sep 17 00:00:00 2001
From: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
Date: Sat, 4 Jul 2020 19:30:39 +0300
Subject: [PATCH 1/1] serial: core: Initialise spin lock before use in
uart_configure_port()
In case of the port to be used as a console we must initialise
a spin lock before use.
Signed-off-by: Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx>
---
drivers/tty/serial/serial_core.c | 7 +++++++
1 file changed, 7 insertions(+)
diff --git a/drivers/tty/serial/serial_core.c
b/drivers/tty/serial/serial_core.c
index 3cc183acf7ba..a81b4900eb60 100644
--- a/drivers/tty/serial/serial_core.c
+++ b/drivers/tty/serial/serial_core.c
@@ -2371,6 +2371,13 @@ uart_configure_port(struct uart_driver *drv,
struct uart_state *state,
/* Power up port for set_mctrl() */
uart_change_pm(state, UART_PM_STATE_ON);
+ /*
+ * If this driver supports console, and it hasn't been
+ * successfully registered yet, initialise spin lock for it.
+ */
+ if (port->cons && !(port->cons->flags & CON_ENABLED))
+ spin_lock_init(&port->lock);
+
/*
* Ensure that the modem control lines are de-activated.
* keep the DTR setting that is set in uart_set_options()
--
2.27.0
Or did you mean to test it in complement of my patch?
No, the idea to avoid "fixing" driver as you rightfully noticed a
double init issue.
This certainly keeps lockdep quiet on my system. You probably want
to set the lockdep class whilst you're at it (keeping that code
common with uart_port_spin_lock_init).
Thanks,
M.
--
Jazz is not dead. It just smells funny...
