Re: [RFC PATCH] tty: serial: msm_serial: Don't reset uart on set_termios

[Stephen Boyd]

On 06/13/2016 12:02 PM, Bjorn Andersson wrote:
> Upon opening the tty, uart_open() ends up calling msm_set_baud_rate()
> which resets the uart block. If this happens as we're coming out of
> msm_console_write() a full fifo worth of console output will be
> discarded.
>
> Cc: Stephen Boyd 
> Signed-off-by: Bjorn Andersson 
> ---
>
> As reported here:
> https://bugs.96boards.org/show_bug.cgi?id=378

Urgh. As mentioned in commit a12f1b406f2d (tty: serial: msm: Reset
uartdm after baud rate change, 2014-10-29) we actually need to reset the
hardware sometimes. Perhaps as discussed over IRC we need to take a
different approach here and only reset the hardware if the baud actually
changes? One way to test this would be to try running a getty on the
console and see if input still works.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [RFC PATCH] tty: serial: msm_serial: Don't reset uart on set_termios

[Stephen Boyd]

On 06/13/2016 12:02 PM, Bjorn Andersson wrote:
> Upon opening the tty, uart_open() ends up calling msm_set_baud_rate()
> which resets the uart block. If this happens as we're coming out of
> msm_console_write() a full fifo worth of console output will be
> discarded.
>
> Cc: Stephen Boyd 
> Signed-off-by: Bjorn Andersson 
> ---
>
> As reported here:
> https://bugs.96boards.org/show_bug.cgi?id=378

Urgh. As mentioned in commit a12f1b406f2d (tty: serial: msm: Reset
uartdm after baud rate change, 2014-10-29) we actually need to reset the
hardware sometimes. Perhaps as discussed over IRC we need to take a
different approach here and only reset the hardware if the baud actually
changes? One way to test this would be to try running a getty on the
console and see if input still works.

-- 
Qualcomm Innovation Center, Inc. is a member of Code Aurora Forum,
a Linux Foundation Collaborative Project

Re: [RFC PATCH] tty: serial: msm_serial: Don't reset uart on set_termios

[Pramod Gurav]

On 14 June 2016 at 00:32, Bjorn Andersson  wrote:
> Upon opening the tty, uart_open() ends up calling msm_set_baud_rate()
> which resets the uart block. If this happens as we're coming out of
> msm_console_write() a full fifo worth of console output will be
> discarded.
>
> Cc: Stephen Boyd 
> Signed-off-by: Bjorn Andersson 
> ---
>
> As reported here:
> https://bugs.96boards.org/show_bug.cgi?id=378
>
>  drivers/tty/serial/msm_serial.c | 18 --
>  1 file changed, 18 deletions(-)

Thanks for the patch.

I no longer see these corruptions with this patch. This is what I used
to see on my DB410C with debain FS:
http://paste.ubuntu.com/17319106/

Tested-by: Pramod Gurav 

Regards,
Pramod

Re: [RFC PATCH] tty: serial: msm_serial: Don't reset uart on set_termios

[Pramod Gurav]

On 14 June 2016 at 00:32, Bjorn Andersson  wrote:
> Upon opening the tty, uart_open() ends up calling msm_set_baud_rate()
> which resets the uart block. If this happens as we're coming out of
> msm_console_write() a full fifo worth of console output will be
> discarded.
>
> Cc: Stephen Boyd 
> Signed-off-by: Bjorn Andersson 
> ---
>
> As reported here:
> https://bugs.96boards.org/show_bug.cgi?id=378
>
>  drivers/tty/serial/msm_serial.c | 18 --
>  1 file changed, 18 deletions(-)

Thanks for the patch.

I no longer see these corruptions with this patch. This is what I used
to see on my DB410C with debain FS:
http://paste.ubuntu.com/17319106/

Tested-by: Pramod Gurav 

Regards,
Pramod