First, checking tty->receive_room to signalize whether there is enough space
in the tty buffers does not make much sense. Provided the tty buffers
are in tty_port and those are not checked at all.
Second, if the rx path is throttled, with CRTSCTS, RTS is deasserted,
but is never asserted again. This leads to port "lockup", not accepting
any more input.
So:
1) stty -F /dev/ttyMI0 crtscts # the mxser port
2) stty -F /dev/ttyS6 crtscts # the connected port
3) cat /dev/ttyMI0
4) "write in a loop" to /dev/ttyS6
5) cat from 3) produces the bytes from 4)
6) killall -STOP cat (the 3)'s one)
7) wait for RTS to drop on /dev/ttyMI0
8) killall -CONT cat (again the 3)'s one)
cat erroneously produces no more output now (i.e. no data sent from
ttyS6 to ttyMI can be seen).
Note that the step 7) is performed twice: once from n_tty by
tty_throttle_safe(), once by mxser_stoprx() from the receive path. Then
after step 7), n_tty correctly unthrottles the input, but mxser calls
mxser_stoprx() again as there is still only a little space in n_tty
buffers (tty->receive_room mentioned at the beginning), but the device's
FIFO is/can be already filled.
After this patch, the output is correctly resumed, i.e. n_tty both
throttles and unthrottles without interfering with mxser's attempts.
This allows us to get rid of the non-standard ldisc_stop_rx flag from
struct mxser_port.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-15-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
I fail to see the point of calling mxser_flush_buffer() from
mxser_close():
1) The SW xmit buffer is freed in mxser_shutdown_port() right after the
call to mxser_flush_buffer(). And all 'cnt', 'head', and 'tail' are
properly initialized to 0 in mxser_activate().
2) The HW buffer is flushed in mxser_shutdown_port() via
mxser_disable_and_clear_FIFO() too.
So the effect of doing it by mxser_flush_buffer() in mxser_close() is
none. Hence remove it, so that when we use tty_port_close() later, the
code is 1:1 identical.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-10-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mxser_stop_rx() should be called from mxser_shutdown_port() for several
reasons:
1) info->slock is held while manipulating IER (as on other places),
2) hangup now stops rx too,
3) mxser_close() will use tty_port_close() and there is no place except
tty_port_operations::shutdown() where this can be done,
4) this is the same sequence as serial_core does. So we can map this
code 1:1 when switching the driver to it.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-9-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The port->icount.tx is handled in a too complicated manner. Instead of
remembering the original count and subtracting the new one from it,
simply increase tx for each character in the loop. No need for cnt
variable then.
Change also the "X = X & Y" assignment to simpler "X &= Y".
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The others are superfluous with tty refcounting in place now. And they
are racy in fact:
* tty_port_initialized() reports false for a small moment after
interrupts are enabled.
* closing is 1 while the port is still alive.
The queues are flushed later during close anyway. So there is no need
for this special handling. Actually, the ISR should not flush the
queues. It should behave as every other driver, just queue the chars
into tty buffer and go on. But this will be changed later. There is
still a lot code depending on having tty in ISR (and not only tty_port).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mxser_close() behaves like this:
-> tty_port_close_start()
-> tty_wait_until_sent()
-> mxser_wait_until_sent()
-> mxser_close_port
-> wait for TEMT
So it is already waited for TEMT through mxser_wait_until_sent() and
there is another round of waiting in mxser_close_port(). The latter one
is superfluous as nothing could be filled into the output FIFO. Remove
the call.
This helps unification among drivers (so that all behave the same) and
future use of tty_port_close().
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20211118073125.12283-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
We force the FCR contents on many places in the code instead of writing
what was actually set in mxser_change_speed() (by ->activate() or
->set_serial_info()).
So introduce mxser_port::FCR to hold the proper contents and bitwise-OR
the value to what needs to be set on all those locations. That is,
clearing RX and/or TX FIFOs. Those flags are self-clearing, so no need
to set them to mxser_port::FCR.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210922075938.31390-7-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The UART_FCR register is write-only. When reading it, one gets contents
of (read-only) UART_IIR instead as they are shared. This mistake was
performed in mxser_flush_buffer() to clear FIFOs.
Actually FCR handling throughout the driver is completely broken. On
many places, it respects neither mu860 settings, nor FIFO (16450 vs
16550) setting. This patch doesn't help to fix this, it actually does
the same. We will introduce a mxser_port::FCR in the next patch to fix
this issue.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210922075938.31390-6-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Provided FIFO is always enabled for MUST chips, move its FCR setting out
of PORT_8250/PORT_16450 special case in mxser_change_speed(). Now, we
can pre-set fcr to zero and invert the condition of the 'if'.
This makes the code more readable (no functional change intended).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210922075938.31390-4-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
mxser_receive_chars_old() is used whenever MOXA_MUST_LSR_RERR is set in
status no matter the HW ID (the last 'if'). So there is no need for
another check of MOXA_MUST_LSR_RERR _with_ hwid == MOXA_MUST_MU860_HWID
(the third 'if'). Hence remove this subcase. That allows us to check
status on a single line with both UART_LSR_BRK_ERROR_BITS (from the
second 'if') and MOXA_MUST_LSR_RERR (the last 'if').
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210922075938.31390-2-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
If a user tries to set a too high rate, it fails due to check in
mxser_set_baud(). But the high rate remains set in termios, so the user
might think everything went smooth. Restore the baud rate from the
old_termios if this happens, so that user knows nothing was changed in
fact.
It used to behave the correct way many years ago, but somehow the
restoration vanished with commit 1c45607ad3 (Char: mxser, remove it)
-- the commit removed mxser's older clone.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210922075938.31390-1-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Starting and stopping TX is performed on many places in the driver. It
is repeated outb and info->IER modification. Create few helpers
(__mxser_start_tx, mxser_start_tx, __mxser_stop_tx) and use them in the
code instead of open coding.
This should be a base for an uart driver for this device in the future.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-60-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
TX is not supposed to be started from tty_operations::put_char. Line
disciplines ought to call tty_operations::put_char several times and
then do a single tty_operations::flush_chars to start TX.
Fix this in mxser by removing TX startup from mxser_put_char.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-58-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Many boards have only 2 ports. But we always allocate 8 ports (struct
mxser_port) in each struct mxser_board.
Switch this to an empty/variable sized array ([]) and allocate the
needed number of ports using struct_size helper in ->probe.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-54-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
There is no need to preallocate an array of four struct mxser_board's.
In most cases a single board or two will be present in a machine. So
allocate struct mxser_board as needed in ->probe.
This makes mxser_boards a bit array. There we store which indexes are
free (unallocated).
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-53-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Rename process_txrx_fifo to mxser_process_txrx_fifo and:
* remove useless parentheses
* return from the 'if's true branch and process the rest in normal code
flow (shift the code one level left)
All this to make the code more readable.
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
Link: https://lore.kernel.org/r/20210618061516.662-50-jslaby@suse.cz
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
