serial: 8250_dw: always set baud rate in dw8250_set_termios
Subsystems (3)
PATCH 1/1 serial: 8250_dw: always set baud rate in dw8250_set_termios
dw8250_set_termios() doesn't set baud rate if the arg "old ktermios" is NULL. This happens during resume.
Call Trace: ... [ 54.928108] dw8250_set_termios+0x162/0x170 [ 54.928114] serial8250_set_termios+0x17/0x20 [ 54.928117] uart_change_speed+0x64/0x160 [ 54.928119] uart_resume_port
...
So the baud rate is not restored after S3 and breaks the apps who use UART, for example, console and bluetooth etc.
We address this issue by setting the baud rate irrespective of arg "old", just like the drivers for other 8250 IPs. This is tested with Intel Broxton platform.
---
We found UART based apps such as console and bluetooth etc. are broken after S3 on Intel Broxton platform. The further debug shows that the baud rate of all UARTs are different with our settings after S3. During S3, the 8250 related IPs may lose power and thus lose the OS's baud rate setting. The driver should restore it during resume. However, Desinware 8250's driver doesn't restore the baud if the arg "old ktermios" is NULL. Unfortunely, it get a NULL arg from serial_core and skips this step in resume path.
Andy guide me that he doesn't see other 8250 IPs judge old==NULL to set baud.
With the modification in this email, the baud rate is OK after S3. A local quick test doesn't show any error. Report the issue here and hope some serial experts can present formal patch to fix.
drivers/tty/serial/8250/8250_dw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)
drivers/tty/serial/8250/8250_dw.c +1 -1
@@ -250,7 +250,7 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios,long rate;int ret; -if (IS_ERR (d->clk) || !old) +if (IS_ERR (d->clk)) goto out;clk_disable_unprepare (d->clk);
Signature · 1 line
2.13.0
Quoted 9 lines · Chen Hu
dw8250_set_termios()doesn't set baud rate if the arg "old ktermios" is
NULL. This happens during resume.Call Trace: ... [ 54.928108] dw8250_set_termios+0x162/0x170 [ 54.928114] serial8250_set_termios+0x17/0x20 [ 54.928117] uart_change_speed+0x64/0x160 [ 54.928119] uart_resume_port
Quoted 8 lines
...
So the baud rate is not restored after S3 and breaks the apps who use UART, for example, console and bluetooth etc.
We address this issue by setting the baud rate irrespective of arg "old", just like the drivers for other 8250 IPs. This is tested with Intel Broxton platform.
You forgot to add
platforms")
Cc: Heikki Krogerus <[email protected]>
The change itself LGTM,
Quoted 43 lines
Signed-off-by Chen Hu <[email protected]>---
We found UART based apps such as console and bluetooth etc. are broken after S3
on Intel Broxton platform. The further debug shows that the baud rate of all
UARTs are different with our settings after S3. During S3, the 8250 related IPs
may lose power and thus lose the OS's baud rate setting. The driver should
restore it during resume. However, Desinware 8250's driver doesn't restore the
baud if the arg "old ktermios" is NULL. Unfortunely, it get a NULL arg fromserial_coreand skips this step in resume path.Andy guide me that he doesn't see other 8250 IPs judge old==NULL to set baud.
With the modification in this email, the baud rate is OK after S3. A local
quick test doesn't show any error. Report the issue here and hope some serial
experts can present formal patch to fix.drivers/tty/serial/8250/8250_dw.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)drivers/tty/serial/8250/8250_dw.c +1
-1@@ -250,7 +250,7 @@ static void dw8250_set_termios(struct uart_port *p, struct ktermios *termios, long rate;int ret; -if (IS_ERR (d->clk) || !old) +if (IS_ERR (d->clk)) goto out;
clk_disable_unprepare(d->clk);
Signature · 2 lines
Andy Shevchenko <[email protected]> Intel Finland Oy