linux-toradex.git/drivers/tty/serial/serial_core.c, branch v4.2.1

serial: core: Fix crashes while echoing when closing

2015-07-24T01:08:28+00:00

While closing, new rx data may be received after the input buffers
have been flushed but before stop_rx() halts receiving [1]. The
new data might not be processed by flush_to_ldisc() until after
uart_shutdown() and normal input processing is re-enabled (ie.,
tty->closing = 0). The race is outlined below:

CPU 0                         | CPU 1
                              |
uart_close()                  |
   tty_port_close_start()     |
      tty->closing = 1        |
      tty_ldisc_flush()       |
                              | => IRQ
                              |   while (LSR & data ready)
                              |      uart_insert_char()
                              |   tty_flip_buffer_push()
                              | <= EOI
   stop_rx()                  |   .
   uart_shutdown()            |   .
      free xmit.buf           |   .
   tty_port_tty_set(NULL)     |   .
   tty->closing = 0           |   .
                              | flush_to_ldisc()
                              |   n_tty_receive_buf_common()
                              |      __receive_buf()
                              |         ...
                              |         commit_echoes()
                              |            uart_flush_chars()
                              |               __uart_start()
                              | ** OOPS on port.tty deref **
   tty_ldisc_flush()          |

Input processing must be prevented from echoing (tty->closing = 1)
until _after_ the input buffers have been flushed again at the end
of uart_close().

[1] In fact, some input may actually be buffered _after_ stop_rx()
since the rx interrupt may have already triggered but not yet been
handled when stop_rx() disables rx interrupts.

Fixes: 2e758910832d ("serial: core: Flush ldisc after dropping port
mutex in uart_close()")
Reported-by: Robert Elliott 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: cleanup in uart_get_baud_rate()

2015-06-13T00:34:36+00:00

Align with coding guidelines:
Replaced a chain of "else if" by a switch case.

Signed-off-by: Joakim Nordell 
Signed-off-by: Greg Kroah-Hartman

serial: earlycon: Add support for big-endian MMIO accesses

2015-05-31T21:55:12+00:00

Support command line parameters of the form:
earlycon=,io|mmio|mmio32|mmio32be,,

This commit seem to be needed even after commit:
serial: 8250: Add support for big-endian MMIO accesses
c627f2ceb692e8a9358b64ac2d139314e7bb0d17

Signed-off-by: Noam Camus 
Signed-off-by: Greg Kroah-Hartman

tty: remove buf parameter from tty_name()

2015-05-06T20:26:57+00:00

tty_name no longer uses the buf parameter, so remove it along with all
the 64 byte stack buffers that used to be passed in.

Mostly generated by the coccinelle script

@depends on patch@
identifier buf;
constant C;
expression tty;
@@
- char buf[C];
  <+...
- tty_name(tty, buf)
+ tty_name(tty)
  ...+>

allmodconfig compiles, so I'm fairly confident the stack buffers
weren't used for other purposes as well.

Signed-off-by: Rasmus Villemoes 
Reviewed-by: Peter Hurley 
Acked-by: Jesper Nilsson 
Acked-by: Dmitry Torokhov 
Signed-off-by: Greg Kroah-Hartman

serial: core: Fix kernel-doc build warnings

2015-04-28T12:26:21+00:00

Fix uart_console_write() kernel-doc build warnings.

Warning(drivers/tty/serial/serial_core.c:1778): No description found for parameter 'putchar'
Warning(drivers/tty/serial/serial_core.c:1778): Excess function parameter 'write' description in 'uart_console_write'

Fixes: 1cfe42b7fd29 ("serial: core: Fix kernel doc for uart_console_write()")
Reported-by: Fengguang Wu 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Fix kernel doc for uart_console_write()

2015-03-26T15:16:20+00:00

'/**' is required to start a kernel-doc comment block.

Acked-by: Rob Herring 
Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: Add minor field to uart_port

2015-03-26T15:10:11+00:00

UART drivers that share ttyS namespace cannot trivially compute the
ttyS index from the port->line value since the minor_start may be
offset from minor 64. Further, to do so requires a pointer to the
uart driver since there is no back pointer from uart_port to
uart_driver.

Rather than have UART drivers computing the minor value by themselves,
encapsulate within the serial core at port registration time.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: earlycon: Refactor parse_options into serial core

2015-03-07T02:55:07+00:00

Prepare to support console-defined matching; refactor the command
line parameter string processing from parse_options() into a
new core function, uart_parse_earlycon(), which decodes command line
parameters of the form:
   earlycon=,io|mmio|mmio32,,
   console=,io|mmio|mmio32,,
   earlycon=,0x,
   console=,0x,

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman

serial: core: replace current->state by __set_current_state()

2015-03-07T02:08:42+00:00

Use helper functions to access current->state.
Direct assignments are prone to races and therefore buggy.

Thanks to Peter Zijlstra for the exact definition of the problem.

Suggested-By: Peter Zijlstra 
Signed-off-by: Fabian Frederick 
Signed-off-by: Greg Kroah-Hartman

serial: core: Rework hw-assisted flow control support

2015-02-02T18:11:28+00:00

hw-assisted flow control support was added to the serial core
in v3.8 with commits,
dba05832cbe4f ("SERIAL: core: add hardware assisted h/w flow control support")
2cbacafd7af0f ("SERIAL: core: add hardware assisted s/w flow control support")
9aba8d5b01119 ("SERIAL: core: add throttle/unthrottle callbacks for hardware
                assisted flow control")
Since then, additional requirements for serial core support have arisen.
Specifically,
1. Separate tx and rx flow control settings for UARTs which only support
   tx flow control (ie., autoCTS).
2. Disable sw-assisted CTS flow control in autoCTS mode
3. Support for RTS flow control by serial core and userspace in autoRTS mode

Distinguish mode from capability; introduce UPSTAT_AUTORTS, UPSTAT_AUTOCTS
and UPSTAT_AUTOXOFF which, when set by the uart driver, enable serial core
support for hw-assisted rx, hw-assisted tx and hw-assisted in-band/IXOFF
rx flow control, respectively. [Note: hw-assisted in-band/IXON tx flow
control does not require serial core support/intervention and can be
enabled by the uart driver when required.]

These modes must be set/reset in the driver's set_termios() method, based
on termios settings, and thus can be safely queried in any context in which
one of the port lock, port mutex or termios rwsem are held. Set these modes
in the 2 in-tree drivers, omap-serial and 8250_omap, which currently
use UPF_HARD_FLOW/UPF_SOFT_FLOW support.

Retain UPF_HARD_FLOW and UPF_SOFT_FLOW as capabilities; re-define
UPF_HARD_FLOW as both UPF_AUTO_RTS and UPF_AUTO_CTS to allow for distinct
and separate rx and tx flow control capabilities.

Disable sw-assisted CTS flow control when UPSTAT_AUTOCTS is enabled.

Signed-off-by: Peter Hurley 
Signed-off-by: Greg Kroah-Hartman