Re: s3c24xx : TIOCM_CTS handling problem

Re: s3c24xx : TIOCM_CTS handling problem

[Matthieu CASTET]

Matthieu CASTET a écrit :
> Hi,
> 
> there is a problem in samsung soc serial driver with the report of
> TIOCM_CTS in get_mctrl.
> 
> The uart layer check the status of the TIOCM_CTS in the open or
> set_termios function and cache the result in the tty->hw_stopped flag.
> 
> Then when sending data, in the function uart_start, it check
> tty->hw_stopped flag before calling the start_tx uart driver callback.
> 
> 
> For the samsung uart driver it means :
> - if the other side is not connected or in a reset state, then CTS
> signal is not activated
> - we open and configure the uart. get_mctrl don't report TIOCM_CTS flag.
> uart layer set tty->hw_stopped flag.
> - we connect or start the other side. CTS signal become activated.
> - we send some characters on the uart. This call uart_write which fill
> uart tx queue and call uart_start. uart_start doesn't call driver
> start_tx because tty->hw_stopped flag is set.
> - because driver start_tx is never call, the data is never send on the uart.
> 
>>From what I see, working driver managing TIOCM_CTS flag (amba-pl011,
> 8250), call uart_handle_cts_change when the uart driver detect a CTS
> signal change (via a interrupt).
> 
> Because the samsung controller doesn't generate an interrupt when CTS
> signal change, we can't call uart_handle_cts_change.
> 
> And easy fix could be to always report TIOCM_CTS.
> 
Ping ?

The bug is still present on git tree and I have got no replies.


Matthieu

Re: s3c24xx : TIOCM_CTS handling problem

[Alan Cox]

> > And easy fix could be to always report TIOCM_CTS.
> > 
> Ping ?
> 
> The bug is still present on git tree and I have got no replies.

Send patches instead then ;)

If the chip can sense the CTS line then you could check on a timer event
but it might be cleaner to add the functionality needed to allow a driver
to say "always call my start_tx" method.

Re: s3c24xx : TIOCM_CTS handling problem

[Matthieu CASTET]

Hi Alan,

Alan Cox a écrit :
>>> And easy fix could be to always report TIOCM_CTS.
>>>
>> Ping ?
>>
>> The bug is still present on git tree and I have got no replies.
> 
> Send patches instead then ;)
> 
> If the chip can sense the CTS line then you could check on a timer event
May be it could be usefull to do something generic that call driver
get_mctrl instead of doing it in the driver (like it is done in
bfin_5xx, sa1100, ...)

> but it might be cleaner to add the functionality needed to allow a driver
> to say "always call my start_tx" method.
Or to say "recheck get_mctrl before my start_tx).
But have you got an idea how the driver could ask that to the serial core ?
flags in struct uart_port seems full.


Matthieu