| Message ID | 20230601141445.11321-1-tony@atomide.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | serial: core: Fix probing serial_base_bus devices | expand |
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
* Greg Kroah-Hartman <gregkh@linuxfoundation.org> [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
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
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
On Thu, Jun 01, 2023 at 06:07:06PM +0300, Tony Lindgren wrote: > * Greg Kroah-Hartman <gregkh@linuxfoundation.org> [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
* Marek Szyprowski <m.szyprowski@samsung.com> [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);
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 @@ -17,6 +17,8 @@ #include "serial_base.h" +static bool serial_base_initialized; + static int serial_base_match(struct device *dev, struct device_driver *drv) { int len = strlen(drv->name); @@ -48,6 +50,11 @@ static int serial_base_device_init(struct uart_port *port, void (*release)(struct device *dev), int id) { + if (!serial_base_initialized) { + dev_err(port->dev, "uart_add_one_port() called before arch_initcall()?\n"); + return -EPROBE_DEFER; + } + device_initialize(dev); dev->type = type; dev->parent = parent_dev; @@ -175,6 +182,8 @@ static int serial_base_init(void) if (ret) goto err_ctrl_exit; + serial_base_initialized = true; + return 0; err_ctrl_exit: @@ -185,7 +194,7 @@ static int serial_base_init(void) return ret; } -module_init(serial_base_init); +arch_initcall(serial_base_init); static void serial_base_exit(void) {
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(). Let's also return an error if a driver attempts to call uart_add_one_port() too early. Reported-by: Marek Szyprowski <m.szyprowski@samsung.com> Closes: https://lore.kernel.org/linux-serial/20230601132012.GB14287@atomide.com/T/#m6a40440fc04d551d27b147da8602e065c982a115 Fixes: 84a9582fd203 ("serial: core: Start managing serial controllers to enable runtime PM") Signed-off-by: Tony Lindgren <tony@atomide.com> --- drivers/tty/serial/serial_base_bus.c | 11 ++++++++++- 1 file changed, 10 insertions(+), 1 deletion(-)