Re: [PATCH] Revert serial 8250 console fixes

[Kumar Gala <galak@kernel.crashing.org>]

On Feb 6, 2006, at 1:38 PM, Alan Cox wrote:

> On Llu, 2006-02-06 at 13:14 -0600, Kumar Gala wrote:
>> Can you explain further why you had to change wait_for_xmitr() from
>> testing BOTH_EMPTY to UART_LSR_THRE.
>
> Because you want to wait for the uart to show that it is ready to  
> accept
> a character, not that the byte has been clocked out entirely. Thats
> essential for working with virtual serial ports on servers as they use
> the fact there is no pending character to work out how to packetize it
> as a TCP stream.
>
>
>> Also, what exactly would you be looking for in a register dump?
>
> When it gets stuck what state are the serial chip registers in and  
> where
> is the OS hanging ?

The following seems to make things better for me.  Can you take a  
look and let me know what you thing.  If it looks good, I'll send  
Russell a clean patch:

- kumar

diff --git a/drivers/serial/8250.c b/drivers/serial/8250.c
index 179c1f0..b1fc97d 100644
--- a/drivers/serial/8250.c
+++ b/drivers/serial/8250.c
@@ -2229,6 +2229,7 @@ serial8250_console_write(struct console
          *      and restore the IER
          */
         wait_for_xmitr(up, BOTH_EMPTY);
+       up->ier |= UART_IER_THRI;
         serial_out(up, UART_IER, ier | UART_IER_THRI);
}