On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> If a physical serial port device driver uses arch_initcall() we fail to
> probe the serial_base_bus devices and the serial port tx fails. This is
> because as serial_base_bus uses module_initcall().
>
> Let's fix the issue by changing serial_base_bus to use arch_initcall().
This will only work if the linking order is such that this will always
come before the drivers. Is that the case here?
thanks,
greg k-h
On 01.06.2023 16:21, Greg Kroah-Hartman wrote:
> On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
>> If a physical serial port device driver uses arch_initcall() we fail to
>> probe the serial_base_bus devices and the serial port tx fails. This is
>> because as serial_base_bus uses module_initcall().
>>
>> Let's fix the issue by changing serial_base_bus to use arch_initcall().
> This will only work if the linking order is such that this will always
> come before the drivers. Is that the case here?
Yes, serial_base_bus is linked as a second object, just after the
serial_core. Device drivers come later.
Best regards
--
Marek Szyprowski, PhD
Samsung R&D Institute Poland
* Greg Kroah-Hartman <[email protected]> [230601 14:21]:
> On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> > If a physical serial port device driver uses arch_initcall() we fail to
> > probe the serial_base_bus devices and the serial port tx fails. This is
> > because as serial_base_bus uses module_initcall().
> >
> > Let's fix the issue by changing serial_base_bus to use arch_initcall().
>
> This will only work if the linking order is such that this will always
> come before the drivers. Is that the case here?
I guess based on Makefile. And also if serial drivers are modules as we
export uart_add_one_port() from serial_base.ko. But yeah this is pretty
fragile potentially.
Hmm maybe we could keep module_init() and then also call serial_base_init()
on uart_add_one_port() path if not yet initialized?
Probably the module_init() should be still there for case when no serial
port device drivers are loaded and serial_base is unloaded..
Regards,
Tony
* Marek Szyprowski <[email protected]> [230601 15:09]:
> On 01.06.2023 16:21, Greg Kroah-Hartman wrote:
> > On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> >> If a physical serial port device driver uses arch_initcall() we fail to
> >> probe the serial_base_bus devices and the serial port tx fails. This is
> >> because as serial_base_bus uses module_initcall().
> >>
> >> Let's fix the issue by changing serial_base_bus to use arch_initcall().
> > This will only work if the linking order is such that this will always
> > come before the drivers. Is that the case here?
>
> Yes, serial_base_bus is linked as a second object, just after the
> serial_core. Device drivers come later.
If we don't want to rely on the Makefile order here, we could do something
like the patch below.
Regards,
Tony
8< ---------------------
diff --git a/drivers/tty/serial/serial_base_bus.c b/drivers/tty/serial/serial_base_bus.c
--- a/drivers/tty/serial/serial_base_bus.c
+++ b/drivers/tty/serial/serial_base_bus.c
@@ -11,12 +11,18 @@
#include <linux/container_of.h>
#include <linux/device.h>
#include <linux/module.h>
+#include <linux/mutex.h>
#include <linux/serial_core.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
#include "serial_base.h"
+static bool serial_base_initialized;
+static DEFINE_MUTEX(serial_base_lock);
+
+static int serial_base_init(void);
+
static int serial_base_match(struct device *dev, struct device_driver *drv)
{
int len = strlen(drv->name);
@@ -48,6 +54,12 @@ static int serial_base_device_init(struct uart_port *port,
void (*release)(struct device *dev),
int id)
{
+ /*
+ * Initialize bus if not yet initialized. Some drivers are using
+ * arch_initcall()
+ */
+ serial_base_init();
+
device_initialize(dev);
dev->type = type;
dev->parent = parent_dev;
@@ -163,6 +175,14 @@ static int serial_base_init(void)
{
int ret;
+ mutex_lock(&serial_base_lock);
+
+ /* Also called from serial_base_device_init() in some cases */
+ if (serial_base_initialized) {
+ ret = 0;
+ goto out_unlock;
+ }
+
ret = bus_register(&serial_base_bus_type);
if (ret)
return ret;
@@ -175,6 +195,10 @@ static int serial_base_init(void)
if (ret)
goto err_ctrl_exit;
+ serial_base_initialized = true;
+
+ mutex_unlock(&serial_base_lock);
+
return 0;
err_ctrl_exit:
@@ -183,15 +207,21 @@ static int serial_base_init(void)
err_bus_unregister:
bus_unregister(&serial_base_bus_type);
+out_unlock:
+ mutex_unlock(&serial_base_lock);
+
return ret;
}
module_init(serial_base_init);
static void serial_base_exit(void)
{
+ mutex_lock(&serial_base_lock);
serial_base_port_exit();
serial_base_ctrl_exit();
bus_unregister(&serial_base_bus_type);
+ serial_base_initialized = false;
+ mutex_unlock(&serial_base_lock);
}
module_exit(serial_base_exit);
--
2.40.1
On Thu, Jun 01, 2023 at 06:07:06PM +0300, Tony Lindgren wrote:
> * Greg Kroah-Hartman <[email protected]> [230601 14:21]:
> > On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> > > If a physical serial port device driver uses arch_initcall() we fail to
> > > probe the serial_base_bus devices and the serial port tx fails. This is
> > > because as serial_base_bus uses module_initcall().
> > >
> > > Let's fix the issue by changing serial_base_bus to use arch_initcall().
> >
> > This will only work if the linking order is such that this will always
> > come before the drivers. Is that the case here?
>
> I guess based on Makefile. And also if serial drivers are modules as we
> export uart_add_one_port() from serial_base.ko. But yeah this is pretty
> fragile potentially.
It's fine, and normal, the Makefile is the ordering here so all is good.
> Hmm maybe we could keep module_init() and then also call serial_base_init()
> on uart_add_one_port() path if not yet initialized?
>
> Probably the module_init() should be still there for case when no serial
> port device drivers are loaded and serial_base is unloaded..
I'll leave this as-is, it looks correct, and I'll queue it up now,
thanks.
greg k-h
On Thu, Jun 01, 2023 at 05:09:52PM +0200, Marek Szyprowski wrote:
> On 01.06.2023 16:21, Greg Kroah-Hartman wrote:
> > On Thu, Jun 01, 2023 at 05:14:44PM +0300, Tony Lindgren wrote:
> >> If a physical serial port device driver uses arch_initcall() we fail to
> >> probe the serial_base_bus devices and the serial port tx fails. This is
> >> because as serial_base_bus uses module_initcall().
> >>
> >> Let's fix the issue by changing serial_base_bus to use arch_initcall().
> > This will only work if the linking order is such that this will always
> > come before the drivers. Is that the case here?
>
> Yes, serial_base_bus is linked as a second object, just after the
> serial_core. Device drivers come later.
Oh good, I guess it wouldn't work at all as the serial_core is needed by
all of those drivers first too, so this should work, thanks for
checking.
greg k-h