Re: Uartlite - ulite_transmit

From: Michal Simek
Date: Mon Jan 17 2011 - 10:18:07 EST

Peter Korsgaard wrote:
"Michal" == Michal Simek <monstr@xxxxxxxxx> 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.

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?

Last week I have also implemented simple ioctl function for uartlite - just printk to see what happen. Look at the second log below.



If there is defined uartlite ioctl function (but always returns -ENOIOCTLCMD)

Sending select for 192.168.0.100...
Lease of 192.168.0.100 obtaulite_ioctl 5401 bf9b1ed8
n_tty_ioctl
ined, lease time 7200
adding dns 172.16.0.5
adding dns 172.16.10.1
Stuart_open(0) called
arting portmap:

Welcome to
ulite_ioctl 5401 bf9f8a8c
n_tty_ioctl
ulite_ioctl 5402 bf9f8a70
n_tty_ioctl
_____ _ uart_close(0) called, port->count 2
************ 210 362
_ _
| ___ \ | | | | (_)
| |_/ / ___ | |_ __ _ | | _ _ __ _ _ __ __
| __/ / _ \| __| / _` || | | || '_ \ | | | |\ \/ /
| | | __/| |_ | (_| || |____| || | | || |_| | > <
\_| \___| \__| \__,_|\_____/|_||_| |_| \__,_|/_/\_\

on Xilinx-SP605-LTP-full-WB-pc-msr-next-22-watch-wt-mdm

************
uart_open(0) called
ulite_ioctl 5401 bff76a18
n_tty_ioctl
ulite_ioctl 540b 2
n_tty_ioctl
n_tty_ioctl_helper TCFLSH
tty_perform_flush TCIOFLUSH
tty_perform_flush TCOFLUSH
tty_driver_flush_buffer
uart_flush_buffer(0) called
ulite_ioctl 5402 bff769a4
n_tty_ioctl
ulite_ioctl 540b 0
n_tty_ioctl
n_tty_ioctl_helper TCFLSH
tty_perform_flush TCIFLUSH
ulite_ioctl 5401 bff76558
n_tty_ioctl

Xilinx-SP605-LTP-full-WB-pc-msr-next-22-watch-wt-mdm login:


If uarlite ioctl is defined: (cases: TCFLSH, TCGETS, TCSETS) - return 0;
It is interested but maybe implement that function could be enough. What do you think?

Thanks,
Michal


NET: Registered protocol family 17
uart_open(0) called
ulite_startup ------------------------
Freeing unused kernel memory: 11218k freed
ulite_ioctl 5600 bf9d1bc8
n_tty_ioctl
ulite_ioctl TCGETS bf9d1b1c
ulite_ioctl TCSETS bf9d1b00
ulite_ioctl TCGETS bf9d1a8c
ulite_ioctl TCSETS bf9d1a70
ulite_ioctl TCGETS bff204d0
Mounting proc:
Mounting var:
Populatinulite_ioctl TCGETS bfd8b4c0
g /var:
Runningulite_ioctl TCGETS bf87e4c0
local start scripts.
Mounting sysfs:
mdev: initialising /dev
ulite_ioctl TCGETS bf8164c0
Mounting /etc/config:
Populating /etc/culite_ioctl TCGETS bf95a4c0
onfig:
flatfsd:ulite_ioctl TCGETS bf9744c0
Created 8 configulite_ioctl TCGETS bf9434c0
uration files (168 bytes)
Mounting devpts:
Setting hostname:
Bringing up network interfaces:
net eth0: Promiscuous mode disabled.
udhcpc (v1.14.3) started
Sending discover...
Sending select for 192.168.0.100...
Lease of 192.168.0.100 obtaulite_ioctl TCGETS bfa3bed8
ined, lease time 7200
adding dns 172.16.0.5
adding uart_open(0) called
ulite_ioctl TCGETS bf9d1a8c
ulite_ioctl TCSETS bf9d1a70
uart_close(0) called, port->count 2
************ 1dd 362

Starting portmap:

Welcome to
_____ _ _ _
| ___ \ | | | | (_)
| |_/ / ___ | |_ __ _ | | _ _ __ _ _ __ __
| __/ / _ \| __| / _` || | | || '_ \ | | | |\ \/ /
| | | __/| |_ | (_| || |____| || | | || |_| | > <
\_| \___| \__| \__,_|\_____/|_||_| |_| \__,_|/_/\_\

on Xilinx-SP605-LTP-full-WB-pc-msr-next-22-watch-wt-mdm

************
uart_open(0) called
ulite_ioctl TCGETS bfd98a18
ulite_ioctl TCFLSH 2
ulite_ioctl TCSETS bfd989a4
ulite_ioctl TCFLSH 0
ulite_ioctl TCGETS bfd98558

Xilinx-SP605-LTP-full-WB-pc-msr-next-22-watch-wt-mdm login:


--
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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