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SubjectRe: Uartlite - ulite_transmit
Peter Korsgaard wrote:
>>>>>> "Michal" == Michal Simek <monstr@monstr.eu> writes:
>
> Hi,
>
> Michal> Hi Peter,
> Michal> sorry for delay. I had to look at another issue.
>
> No problem.
>
> Michal> Below is full log:
> Michal> 1. I setup baudrate to 50. (It could be possible to set it up to 0 too)
> Michal> That's why I think that doesn't matter what baudrate is setup.
>
> Michal> 2. You see where ulite_startup is called. It is called only once.
>
> Ok, good.
>
> Michal> 3. You see that there is no call __uart_wait_until_sent(). It could be
> Michal> called for ASYNC mode. The second thing is __uart_wait_until_sent
> Michal> function is checking if tx fifo is empty not circ buffer is empty.
>
> Yes, that's afaik what that function should do.
>
> Michal> 4. Next thing is that in uart_close. port->count is 2 which means that
> Michal> the executing path is
> Michal> if (port->count) {
> Michal> spin_unlock_irqrestore(&port->lock, flags);
> Michal> goto done;
> Michal> }
> Michal> which means that there is no chance to call __uart_wait_until_sent
> Michal> function anyway.
>
> And no buffer flushing, so that's fine.
>
> Michal> 5. I did one modification to add simple while loop till circ buffer is
> Michal> empty to the same location to see what happen (timouts are bogus
> Michal> values).
>
> Michal> if (port->count) {
> Michal> spin_unlock_irqrestore(&port->lock, flags);
> Michal> printk("************ %x %x\n", (&uport->state->xmit)->tail,
> Michal> (&uport->state->xmit)->head);
> Michal> while (!uart_circ_empty(&uport->state->xmit)) {
> Michal> msleep_interruptible(jiffies_to_msecs((uport->timeout - HZ/50)));
> Michal> if (signal_pending(current))
> Michal> break;
> Michal> if (time_after(jiffies, jiffies + uport->timeout))
> Michal> break;
> Michal> }
> Michal> printk("************\n");
> Michal> goto done;
> Michal> }
>
> Ok, so this shows that there's still data in the circular buffer when
> uart is closed, like expected.
>
> For me, it all looks normal:
>
> 1. serial port gets opened, uart_open -> uart_startup -> ulite_startup
> gets called, ASYNC_INITIALIZED gets set, circular buffer and hardware
> TX fifo cleared.

But ASYNC_INITIALIZED is not set.

>
> 2. Some time later serial port gets opened again, and uart_startup is a
> NOP because ASYNC_INITIALIZED is set. No circular buffer / hw fifo
> clear.
>
> 3. serial port gets closed, uart_close is a NOP because port->count > 0
>
> 4. serial port gets opened again, NOP like in 2.
>
> The problem is the uart_flush_buffer() call we see after uart_open() in
> 4. If doesn't seem to come from serial_core (only called from uart_close
> / uart_hangup), so presumably it comes from the TTY core or
> userspace. Could you add a bit more debug to figure out where exactly it
> comes from?

ok. will do.

Thanks,
Michal

>
> Michal> ************
> Michal> uart_open(0) called
> Michal> uart_flush_buffer(0) called
>


--
Michal Simek, Ing. (M.Eng)
w: www.monstr.eu p: +42-0-721842854
Maintainer of Linux kernel 2.6 Microblaze Linux - http://www.monstr.eu/fdt/
Microblaze U-BOOT custodian


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