| Message ID | 20200705092736.1030598-1-maz@kernel.org (mailing list archive) |
|---|---|
| State | Not Applicable |
| Headers | show |
| Series | tty: serial: meson_uart: Init port lock early | expand |
On Sun, Jul 5, 2020 at 12:32 PM Marc Zyngier <maz@kernel.org> 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@linux.intel.com/T/#m9255e2a7474b160e66c7060fca5323ca3df49cfd > Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console") > Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> > Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> > Signed-off-by: Marc Zyngier <maz@kernel.org> > --- > drivers/tty/serial/meson_uart.c | 3 +++ > 1 file changed, 3 insertions(+) > > diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c > index d2c08b760f83..386e39c90628 100644 > --- a/drivers/tty/serial/meson_uart.c > +++ b/drivers/tty/serial/meson_uart.c > @@ -759,6 +759,9 @@ static int meson_uart_probe(struct platform_device *pdev) > if (ret) > return ret; > > + /* Init the spinlock early in case this is the console */ > + spin_lock_init(&port->lock); > + > port->iotype = UPIO_MEM; > port->mapbase = res_mem->start; > port->mapsize = resource_size(res_mem); > -- > 2.26.2 >
On 2020-07-05 11:07, Andy Shevchenko wrote: > On Sun, Jul 5, 2020 at 12:32 PM Marc Zyngier <maz@kernel.org> 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@linux.intel.com/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). Or did you mean to test it in complement of my patch? M.
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@kernel.org> 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@linux.intel.com/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@linux.intel.com> 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@linux.intel.com> --- 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()
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@kernel.org> 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@linux.intel.com/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@linux.intel.com> > 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@linux.intel.com> > --- > 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.
diff --git a/drivers/tty/serial/meson_uart.c b/drivers/tty/serial/meson_uart.c index d2c08b760f83..386e39c90628 100644 --- a/drivers/tty/serial/meson_uart.c +++ b/drivers/tty/serial/meson_uart.c @@ -759,6 +759,9 @@ static int meson_uart_probe(struct platform_device *pdev) if (ret) return ret; + /* Init the spinlock early in case this is the console */ + spin_lock_init(&port->lock); + port->iotype = UPIO_MEM; port->mapbase = res_mem->start; port->mapsize = resource_size(res_mem);
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. Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console") Cc: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Marc Zyngier <maz@kernel.org> --- drivers/tty/serial/meson_uart.c | 3 +++ 1 file changed, 3 insertions(+)