linux-stable.git/drivers/tty, branch v3.2.31

pch_uart: Add eg20t_port lock field, avoid recursive spinlocks

2012-10-10T02:31:12+00:00

commit 2588aba002d14e938c2f56d299ecf3e7ce1302a5 upstream.

pch_uart_interrupt() takes priv->port.lock which leads to two recursive
spinlock calls if low_latency==1 or CONFIG_PREEMPT_RT_FULL=y (one
otherwise):

pch_uart_interrupt
  spin_lock_irqsave(priv->port.lock, flags)
  case PCH_UART_IID_RDR_TO (data ready)
  handle_rx_to
    push_rx
      tty_port_tty_get
        spin_lock_irqsave(&port->lock, flags) <--- already hold this lock
        ...
      tty_flip_buffer_push
        ...
        flush_to_ldisc
          spin_lock_irqsave(&tty->buf.lock)
            spin_lock_irqsave(&tty->buf.lock)
            disc->ops->receive_buf(tty, char_buf)
              n_tty_receive_buf
                tty->ops->flush_chars()
                uart_flush_chars
                  uart_start
                    spin_lock_irqsave(&port->lock) <--- already hold this lock

Avoid this by using a dedicated lock to protect the eg20t_port structure
and IO access to its membase. This is more consistent with the 8250
driver.  Ensure priv->lock is always take prior to priv->port.lock when
taken at the same time.

V2: Remove inadvertent whitespace change.
V3: Account for oops_in_progress for the private lock in
    pch_console_write().

Note: Like the 8250 driver, if a printk is introduced anywhere inside
      the pch_console_write() critical section, the kernel will hang
      on a recursive spinlock on the private lock. The oops case is
      handled by using a trylock in the oops_in_progress case.

Signed-off-by: Darren Hart 
CC: Tomoya MORINAGA 
CC: Feng Tang 
CC: Alexander Stein 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.2:
 - Adjust context
 - Drop changes to pch_console_write()]
Signed-off-by: Ben Hutchings

tty: serial: imx: don't reinit clock in imx_setup_ufcr()

2012-09-19T14:05:14+00:00

commit 7be0670f7b9198382938a03ff3db7f47ef6b4780 upstream.

Remove the clock configuration from imx_setup_ufcr(). This
isn't needed here and will cause garbage output if done.

To be be sure that we only touch the bits we want (TXTL and RXTL)
we have to mask out all other bits of the UFCR register. Add
one non-existing bit macro for this, too (bit 6, DCEDTE on i.MX6).

Signed-off-by: Dirk Behme 
CC: Shawn Guo 
CC: Sascha Hauer 
CC: Troy Kisky 
CC: Xinyu Chen 
Acked-by: Shawn Guo 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.2: deleted code in imx_setup_ufcr() refers to
 sport->clk not sport->clk_per]
Signed-off-by: Ben Hutchings

tty: serial: imx: console write routing is unsafe on SMP

2012-09-19T14:05:14+00:00

commit 9ec1882df244c4ee1baa692676fef5e8b0f5487d upstream.

The console feature's write routing is unsafe on SMP with
the startup/shutdown call.

There could be several consumers of the console
* the kernel printk
* the init process using /dev/kmsg to call printk to show log
* shell, which open /dev/console and write with sys_write()

The shell goes into the normal uart open/write routing,
but the other two go into the console operations.
The open routing calls imx serial startup, which will write USR1/2
register without any lock and critical with imx_console_write call.

Add a spin_lock for startup/shutdown/console_write routing.

This patch is a port from Freescale's Android kernel.

Signed-off-by: Xinyu Chen 
Tested-by: Dirk Behme 
CC: Sascha Hauer 
Acked-by: Shawn Guo 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.2: adjust context]
Signed-off-by: Ben Hutchings

pmac_zilog,kdb: Fix console poll hook to return instead of loop

2012-09-12T02:37:34+00:00

commit 38f8eefccf3a23c4058a570fa2938a4f553cf8e0 upstream.

kdb <-> kgdb transitioning does not work properly with this UART
driver because the get character routine loops indefinitely as opposed
to returning NO_POLL_CHAR per the expectation of the KDB I/O driver
API.

The symptom is a kernel hang when trying to switch debug modes.

Cc: Alan Cox 
Signed-off-by: Jason Wessel 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

pch_uart: Fix parity setting issue

2012-08-09T23:25:19+00:00

commit 38bd2a1ac736901d1cf4971c78ef952ba92ef78b upstream.

Parity Setting value is reverse.
E.G. In case of setting ODD parity, EVEN value is set.
This patch inverts "if" condition.

Signed-off-by: Tomoya MORINAGA 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

pch_uart: Fix rx error interrupt setting issue

2012-08-09T23:25:18+00:00

commit 9539dfb7ac1c84522fe1f79bb7dac2990f3de44a upstream.

Rx Error interrupt(E.G. parity error) is not enabled.
So, when parity error occurs, error interrupt is not occurred.
As a result, the received data is not dropped.

This patch adds enable/disable rx error interrupt code.

Signed-off-by: Tomoya MORINAGA 
Acked-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman 
[Backported by Tomoya MORINGA: adjusted context]
Signed-off-by: Ben Hutchings

pch_uart: Fix missing break for 16 byte fifo

2012-08-09T23:25:17+00:00

commit 9bc03743fff0770dc5a5324ba92e67cc377f16ca upstream.

Otherwise we fall back to the wrong value.

Reported-by: 
Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=44091
Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

tty: Allow uart_register/unregister/register

2012-05-30T23:43:42+00:00

commit 1e66cded334e6cea596c72f6f650eec351b1e959 upstream.

This is legitimate but because we don't clear the drv->state pointer in the
unregister code causes a bogus BUG().

Resolves-bug: https://bugzilla.kernel.org/show_bug.cgi?id=42880
Signed-off-by: Alan Cox 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

Add missing call to uart_update_timeout()

2012-05-30T23:43:36+00:00

commit 8b979f7c6bf13a57e7b6002f1175312a44773960 upstream.

This patch fixes a problem reported here:
http://article.gmane.org/gmane.linux.ports.arm.kernel/155242/match=auart

Signed-off-by: Lothar Waßmann 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

8250.c: less than 2400 baud fix.

2012-05-30T23:43:34+00:00

commit f9a9111b540fd67db5dab332f4b83d86c90e27b1 upstream.

We noticed that we were loosing data at speed less than 2400 baud.
It turned out our (TI16750 compatible) uart with 64 byte outgoing fifo
was truncated to 16 byte (bit 5 sets fifo len) when modifying the fcr
reg.
The input code still fills the buffer with 64 bytes if I remember
correctly and thus data is lost.
Our fix was to remove whiping of the fcr content and just add the
TRIGGER_1 which we want for latency.
I can't see why this would not work on less than 2400 always, for all
uarts ...
Otherwise one would have to make sure the filling of the fifo re-checks
the current state of available fifo size (urrk).

Signed-off-by: Christian Melki 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.2: adjust filename; replace *port with up->port]
Signed-off-by: Ben Hutchings