[PATCH v2 0/2] serial: imx: fix unregister/register console

[PATCH v2 0/2] serial: imx: fix unregister/register console

[Francesco Dolcini]

Hi,
here a couple of fixes to properly handle imx serial console
unregister/register at runtime.

The patch from Stefan was already posted years ago but never merged [1],
however is still valid and it's pretty easy to trigger the problem. We have
this patch in our kernel tree since 3 years, but for some reason we never
managed to upstream it.

As correctly wrote by Uwe [2] this issue affects multiple drivers, I could
provide a patch for those, but I will not have any way to test it.

The second patch is required to have a balanced clock enable/disable
when doing console register/unregister.

The issue is present at least since
a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")

[1] https://marc.info/?l=linux-serial&m=154221779312036&w=2
[2] https://lore.kernel.org/all/20211014081028.xafpuzrxk3jvv5qn@pengutronix.de/

Changes in v2:
  Improved commit message and added fixes tag.
 
---

Francesco Dolcini (1):
  serial: imx: disable console clocks on unregister

Stefan Agner (1):
  serial: imx: fix detach/attach of serial console

 drivers/tty/serial/imx.c | 16 ++++++++++++++--
 1 file changed, 14 insertions(+), 2 deletions(-)

-- 
2.25.1


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[PATCH v2 1/2] serial: imx: fix detach/attach of serial console

[Francesco Dolcini]

From: Stefan Agner <stefan@agner.ch>

If the device used as a serial console gets detached/attached at runtime,
register_console() will try to call imx_uart_setup_console(), but this
is not possible since it is marked as __init.

For instance

  # cat /sys/devices/virtual/tty/console/active
  tty1 ttymxc0
  # echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
  # echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console

[   73.166649] 8<--- cut here ---
[   73.167005] Unable to handle kernel paging request at virtual address c154d928
[   73.167601] pgd = 55433e84
[   73.167875] [c154d928] *pgd=8141941e(bad)
[   73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
[   73.168429] Modules linked in:
[   73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
[   73.168675] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
[   73.168791] PC is at imx_uart_console_setup+0x0/0x238
[   73.168927] LR is at try_enable_new_console+0x98/0x124
[   73.169056] pc : [<c154d928>]    lr : [<c0196f44>]    psr: a0000013
[   73.169178] sp : c2ef5e70  ip : 00000000  fp : 00000000
[   73.169281] r10: 00000000  r9 : c02cf970  r8 : 00000000
[   73.169389] r7 : 00000001  r6 : 00000001  r5 : c1760164  r4 : c1e0fb08
[   73.169512] r3 : c154d928  r2 : 00000000  r1 : efffcbd1  r0 : c1760164
[   73.169641] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
[   73.169782] Control: 10c5387d  Table: 8345406a  DAC: 00000051
[   73.169895] Register r0 information: non-slab/vmalloc memory
[   73.170032] Register r1 information: non-slab/vmalloc memory
[   73.170158] Register r2 information: NULL pointer
[   73.170273] Register r3 information: non-slab/vmalloc memory
[   73.170397] Register r4 information: non-slab/vmalloc memory
[   73.170521] Register r5 information: non-slab/vmalloc memory
[   73.170647] Register r6 information: non-paged memory
[   73.170771] Register r7 information: non-paged memory
[   73.170892] Register r8 information: NULL pointer
[   73.171009] Register r9 information: non-slab/vmalloc memory
[   73.171142] Register r10 information: NULL pointer
[   73.171259] Register r11 information: NULL pointer
[   73.171375] Register r12 information: NULL pointer
[   73.171494] Process sh (pid: 536, stack limit = 0xcd1ba82f)
[   73.171621] Stack: (0xc2ef5e70 to 0xc2ef6000)
[   73.171731] 5e60:                                     ???????? ???????? ???????? ????????
[   73.171899] 5e80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172059] 5ea0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172217] 5ec0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172377] 5ee0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172537] 5f00: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172698] 5f20: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.172856] 5f40: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173016] 5f60: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173177] 5f80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173336] 5fa0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173496] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173654] 5fe0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
[   73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
[   73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)
[   73.174470] [<c0383718>] (kernfs_fop_write_iter) from [<c02cf5f4>] (vfs_write+0x31c/0x548)
[   73.174679] [<c02cf5f4>] (vfs_write) from [<c02cf970>] (ksys_write+0x60/0xec)
[   73.174863] [<c02cf970>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x1c)
[   73.175052] Exception stack(0xc2ef5fa8 to 0xc2ef5ff0)
[   73.175167] 5fa0:                   ???????? ???????? ???????? ???????? ???????? ????????
[   73.175327] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
[   73.175486] 5fe0: ???????? ???????? ???????? ????????
[   73.175608] Code: 00000000 00000000 00000000 00000000 (00000000)
[   73.175744] ---[ end trace 9b75121265109bf1 ]---

A similar issue could be triggered unbinding/binding the serial console
device [*].

Drop __init so that imx_uart_setup_console() can be safely called at
runtime.

[*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/

Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
Signed-off-by: Stefan Agner <stefan@agner.ch>
Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
 drivers/tty/serial/imx.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 8b121cd869e9..51a9f9423b1a 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2017,7 +2017,7 @@ imx_uart_console_write(struct console *co, const char *s, unsigned int count)
  * If the port was already initialised (eg, by a boot loader),
  * try to determine the current setup.
  */
-static void __init
+static void
 imx_uart_console_get_options(struct imx_port *sport, int *baud,
 			     int *parity, int *bits)
 {
@@ -2076,7 +2076,7 @@ imx_uart_console_get_options(struct imx_port *sport, int *baud,
 	}
 }
 
-static int __init
+static int
 imx_uart_console_setup(struct console *co, char *options)
 {
 	struct imx_port *sport;
-- 
2.25.1


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[PATCH v2 2/2] serial: imx: disable console clocks on unregister

[Francesco Dolcini]

During console setup imx_uart_console_setup() enables clocks, but they
are never disabled when the console is unregistered, this leads to
clk_prepare_enable() being called multiple times without a matching
clk_disable_unprepare() in case of console unregister.

Ensure that clock enable/disable are balanced adding
clk_disable_unprepare() in the console exit callback.

Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
---
 drivers/tty/serial/imx.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/drivers/tty/serial/imx.c b/drivers/tty/serial/imx.c
index 51a9f9423b1a..90f82e6c54e4 100644
--- a/drivers/tty/serial/imx.c
+++ b/drivers/tty/serial/imx.c
@@ -2124,12 +2124,24 @@ imx_uart_console_setup(struct console *co, char *options)
 	return retval;
 }
 
+static int
+imx_uart_console_exit(struct console *co)
+{
+	struct imx_port *sport = imx_uart_ports[co->index];
+
+	clk_disable_unprepare(sport->clk_per);
+	clk_disable_unprepare(sport->clk_ipg);
+
+	return 0;
+}
+
 static struct uart_driver imx_uart_uart_driver;
 static struct console imx_uart_console = {
 	.name		= DEV_NAME,
 	.write		= imx_uart_console_write,
 	.device		= uart_console_device,
 	.setup		= imx_uart_console_setup,
+	.exit		= imx_uart_console_exit,
 	.flags		= CON_PRINTBUFFER,
 	.index		= -1,
 	.data		= &imx_uart_uart_driver,
-- 
2.25.1


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Re: [PATCH v2 1/2] serial: imx: fix detach/attach of serial console

[Uwe Kleine-König]

[-- Attachment #1.1: Type: text/plain, Size: 5543 bytes --]

On Wed, Oct 20, 2021 at 09:26:42PM +0200, Francesco Dolcini wrote:
> From: Stefan Agner <stefan@agner.ch>
> 
> If the device used as a serial console gets detached/attached at runtime,
> register_console() will try to call imx_uart_setup_console(), but this
> is not possible since it is marked as __init.
> 
> For instance
> 
>   # cat /sys/devices/virtual/tty/console/active
>   tty1 ttymxc0
>   # echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
>   # echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
> 
> [   73.166649] 8<--- cut here ---
> [   73.167005] Unable to handle kernel paging request at virtual address c154d928
> [   73.167601] pgd = 55433e84
> [   73.167875] [c154d928] *pgd=8141941e(bad)
> [   73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
> [   73.168429] Modules linked in:
> [   73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
> [   73.168675] Hardware name: Freescale i.MX6 Ultralite (Device Tree)
> [   73.168791] PC is at imx_uart_console_setup+0x0/0x238
> [   73.168927] LR is at try_enable_new_console+0x98/0x124
> [   73.169056] pc : [<c154d928>]    lr : [<c0196f44>]    psr: a0000013
> [   73.169178] sp : c2ef5e70  ip : 00000000  fp : 00000000
> [   73.169281] r10: 00000000  r9 : c02cf970  r8 : 00000000
> [   73.169389] r7 : 00000001  r6 : 00000001  r5 : c1760164  r4 : c1e0fb08
> [   73.169512] r3 : c154d928  r2 : 00000000  r1 : efffcbd1  r0 : c1760164
> [   73.169641] Flags: NzCv  IRQs on  FIQs on  Mode SVC_32  ISA ARM  Segment none
> [   73.169782] Control: 10c5387d  Table: 8345406a  DAC: 00000051
> [   73.169895] Register r0 information: non-slab/vmalloc memory
> [   73.170032] Register r1 information: non-slab/vmalloc memory
> [   73.170158] Register r2 information: NULL pointer
> [   73.170273] Register r3 information: non-slab/vmalloc memory
> [   73.170397] Register r4 information: non-slab/vmalloc memory
> [   73.170521] Register r5 information: non-slab/vmalloc memory
> [   73.170647] Register r6 information: non-paged memory
> [   73.170771] Register r7 information: non-paged memory
> [   73.170892] Register r8 information: NULL pointer
> [   73.171009] Register r9 information: non-slab/vmalloc memory
> [   73.171142] Register r10 information: NULL pointer
> [   73.171259] Register r11 information: NULL pointer
> [   73.171375] Register r12 information: NULL pointer
> [   73.171494] Process sh (pid: 536, stack limit = 0xcd1ba82f)
> [   73.171621] Stack: (0xc2ef5e70 to 0xc2ef6000)
> [   73.171731] 5e60:                                     ???????? ???????? ???????? ????????
> [   73.171899] 5e80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172059] 5ea0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172217] 5ec0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172377] 5ee0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172537] 5f00: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172698] 5f20: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.172856] 5f40: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173016] 5f60: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173177] 5f80: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173336] 5fa0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173496] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173654] 5fe0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
> [   73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
> [   73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)
> [   73.174470] [<c0383718>] (kernfs_fop_write_iter) from [<c02cf5f4>] (vfs_write+0x31c/0x548)
> [   73.174679] [<c02cf5f4>] (vfs_write) from [<c02cf970>] (ksys_write+0x60/0xec)
> [   73.174863] [<c02cf970>] (ksys_write) from [<c0100080>] (ret_fast_syscall+0x0/0x1c)
> [   73.175052] Exception stack(0xc2ef5fa8 to 0xc2ef5ff0)
> [   73.175167] 5fa0:                   ???????? ???????? ???????? ???????? ???????? ????????
> [   73.175327] 5fc0: ???????? ???????? ???????? ???????? ???????? ???????? ???????? ????????
> [   73.175486] 5fe0: ???????? ???????? ???????? ????????
> [   73.175608] Code: 00000000 00000000 00000000 00000000 (00000000)
> [   73.175744] ---[ end trace 9b75121265109bf1 ]---
> 
> A similar issue could be triggered unbinding/binding the serial console
> device [*].
> 
> Drop __init so that imx_uart_setup_console() can be safely called at
> runtime.
> 
> [*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/
> 
> Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

-- 
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Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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Re: [PATCH v2 1/2] serial: imx: fix detach/attach of serial console

[Andy Shevchenko]

On Wed, Oct 20, 2021 at 10:27 PM Francesco Dolcini
<francesco.dolcini@toradex.com> wrote:
>
> From: Stefan Agner <stefan@agner.ch>
>
> If the device used as a serial console gets detached/attached at runtime,
> register_console() will try to call imx_uart_setup_console(), but this
> is not possible since it is marked as __init.

Thank you for fixing this!

> For instance
>
>   # cat /sys/devices/virtual/tty/console/active
>   tty1 ttymxc0
>   # echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
>   # echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console

Can we leave only something like below in the commit message?

> [   73.167005] Unable to handle kernel paging request at virtual address c154d928
> [   73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
> [   73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
  ...
> [   73.168791] PC is at imx_uart_console_setup+0x0/0x238
> [   73.168927] LR is at try_enable_new_console+0x98/0x124
  ...
> [   73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
> [   73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
> [   73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)

> A similar issue could be triggered unbinding/binding the serial console

on unbinding/binding

> device [*].
>
> Drop __init so that imx_uart_setup_console() can be safely called at
> runtime.
>
> [*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/

Make it Link: tag?

> Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
> Signed-off-by: Stefan Agner <stefan@agner.ch>
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>

With above nit-picks addressed, FWIW,
Reviewed-by: Andy Shevchenko <andy.shevchenko@gmail.com>

-- 
With Best Regards,
Andy Shevchenko

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Re: [PATCH v2 1/2] serial: imx: fix detach/attach of serial console

[Greg Kroah-Hartman]

On Wed, Oct 20, 2021 at 10:54:26PM +0300, Andy Shevchenko wrote:
> On Wed, Oct 20, 2021 at 10:27 PM Francesco Dolcini
> <francesco.dolcini@toradex.com> wrote:
> >
> > From: Stefan Agner <stefan@agner.ch>
> >
> > If the device used as a serial console gets detached/attached at runtime,
> > register_console() will try to call imx_uart_setup_console(), but this
> > is not possible since it is marked as __init.
> 
> Thank you for fixing this!
> 
> > For instance
> >
> >   # cat /sys/devices/virtual/tty/console/active
> >   tty1 ttymxc0
> >   # echo -n N > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
> >   # echo -n Y > /sys/devices/virtual/tty/console/subsystem/ttymxc0/console
> 
> Can we leave only something like below in the commit message?
> 
> > [   73.167005] Unable to handle kernel paging request at virtual address c154d928
> > [   73.168304] Internal error: Oops: 8000000d [#1] SMP ARM
> > [   73.168522] CPU: 0 PID: 536 Comm: sh Not tainted 5.15.0-rc6-00056-g3968ddcf05fb #3
>   ...
> > [   73.168791] PC is at imx_uart_console_setup+0x0/0x238
> > [   73.168927] LR is at try_enable_new_console+0x98/0x124
>   ...
> > [   73.173826] [<c0196f44>] (try_enable_new_console) from [<c01984a8>] (register_console+0x10c/0x2ec)
> > [   73.174053] [<c01984a8>] (register_console) from [<c06e2c90>] (console_store+0x14c/0x168)
> > [   73.174262] [<c06e2c90>] (console_store) from [<c0383718>] (kernfs_fop_write_iter+0x110/0x1cc)
> 
> > A similar issue could be triggered unbinding/binding the serial console
> 
> on unbinding/binding
> 
> > device [*].
> >
> > Drop __init so that imx_uart_setup_console() can be safely called at
> > runtime.
> >
> > [*] https://lore.kernel.org/all/20181114174940.7865-3-stefan@agner.ch/
> 
> Make it Link: tag?
> 
> > Fixes: a3cb39d258ef ("serial: core: Allow detach and attach serial device for console")
> > Signed-off-by: Stefan Agner <stefan@agner.ch>
> > Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
> 
> With above nit-picks addressed, FWIW,

Those are not a big deal, I'll edit the changelog text...

thanks,

greg k-h

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Re: [PATCH v2 2/2] serial: imx: disable console clocks on unregister

[Uwe Kleine-König]

[-- Attachment #1.1: Type: text/plain, Size: 765 bytes --]

On Wed, Oct 20, 2021 at 09:26:43PM +0200, Francesco Dolcini wrote:
> During console setup imx_uart_console_setup() enables clocks, but they
> are never disabled when the console is unregistered, this leads to
> clk_prepare_enable() being called multiple times without a matching
> clk_disable_unprepare() in case of console unregister.
> 
> Ensure that clock enable/disable are balanced adding
> clk_disable_unprepare() in the console exit callback.
> 
> Signed-off-by: Francesco Dolcini <francesco.dolcini@toradex.com>
Acked-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>

Thanks
Uwe

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Industrial Linux Solutions                 | https://www.pengutronix.de/ |

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