linux-toradex.git/drivers/tty/serial/sh-sci.c, branch v3.0.79

serial: sh-sci: fix a race of DMA submit_tx on transfer

2012-04-02T16:27:22+00:00

commit 49d4bcaddca977fffdea8b0b71f6e5da96dac78e upstream.

When DMA is enabled, sh-sci transfer begins with
 uart_start()
  sci_start_tx()
    if (cookie_tx < 0) schedule_work()
Then, starts DMA when wq scheduled, -- (A)
 process_one_work()
  work_fn_rx()
   cookie_tx = desc->submit_tx()
And finishes when DMA transfer ends, -- (B)
 sci_dma_tx_complete()
  async_tx_ack()
  cookie_tx = -EINVAL
  (possible another schedule_work())

This A to B sequence is not reentrant, since controlling variables
(for example, cookie_tx above) are not queues nor lists. So, they
must be invoked as A B A B..., otherwise results in kernel crash.

To ensure the sequence, sci_start_tx() seems to test if cookie_tx < 0
(represents "not used") to call schedule_work().
But cookie_tx will not be set (to a cookie, also means "used") until
in the middle of work queue scheduled function work_fn_tx().

This gap between the test and set allows the breakage of the sequence
under the very frequently call of uart_start().
Another gap between async_tx_ack() and another schedule_work() results
in the same issue, too.

This patch introduces a new condition "cookie_tx == 0" just to mark
it is "busy" and assign it within spin-locked region to fill the gaps.

Signed-off-by: Takashi Yoshii 
Reviewed-by: Guennadi Liakhovetski 
Signed-off-by: Paul Mundt 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'sh-latest' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6

2011-05-24T04:24:07+00:00

* 'sh-latest' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6: (23 commits)
  sh: Ignore R_SH_NONE module relocations.
  SH: SE7751: Fix pcibios_map_platform_irq prototype.
  sh: remove warning and warning_symbol from struct stacktrace_ops
  sh: wire up sys_sendmmsg.
  clocksource: sh_tmu: Runtime PM support
  clocksource: sh_tmu: __clocksource_updatefreq_hz() update
  clocksource: sh_cmt: Runtime PM support
  clocksource: sh_cmt: __clocksource_updatefreq_hz() update
  dmaengine: shdma: synchronize RCU before freeing, simplify spinlock
  dmaengine: shdma: add runtime- and system-level power management
  dmaengine: shdma: fix locking
  sh: sh-sci: sh7377 and sh73a0 build fixes
  sh: cosmetic improvement: use an existing pointer
  serial: sh-sci: suspend/resume wakeup support V2
  serial: sh-sci: Runtime PM support
  sh: select IRQ_FORCED_THREADING.
  sh: intc: Set virtual IRQs as nothread.
  sh: fixup fpu.o compile order
  i2c: add a module alias to the sh-mobile driver
  ALSA: add a module alias to the FSI driver
  ...

serial: sh-sci: suspend/resume wakeup support V2

2011-05-23T03:22:09+00:00

This patch adds wakeup support to the sh-sci driver. The serial
core deals with all details but defaults to wakeup disabled. So
to make use of this feature enable wakeup in sysfs:

echo enabled > /sys/class/tty/ttySC0/power/wakeup

Signed-off-by: Magnus Damm 
Signed-off-by: Paul Mundt

serial: sh-sci: Runtime PM support

2011-05-23T03:22:04+00:00

Add support for Runtime PM in the sh-sci driver.

Signed-off-by: Magnus Damm 
Signed-off-by: Paul Mundt

tty: remove invalid location line in file header

2011-04-19T23:33:36+00:00

remove invalid location line in each file header after location
moved from driver/char to driver/tty

Signed-off-by: Jovi Zhang 
Signed-off-by: Greg Kroah-Hartman

Merge branch 'sh-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6

2011-04-07T19:48:45+00:00

* 'sh-fixes-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/lethal/sh-2.6:
  sh: select ARCH_NO_SYSDEV_OPS.
  sh: fix build error in board-sh7757lcr.c
  sh: landisk: Remove whitespace
  sh: landisk: Remove mv_nr_irqs
  sh: sh-sci: Fix double initialization by serial_console_setup
  serial: sh-sci: prevent setup of uninitialized serial console
  dma: shdma: add checking the DMAOR_AE in sh_dmae_err

Fix common misspellings

2011-03-31T14:26:23+00:00

Fixes generated by 'codespell' and manually reviewed.

Signed-off-by: Lucas De Marchi

sh: sh-sci: Fix double initialization by serial_console_setup

2011-03-31T05:33:24+00:00

The driver is initialized in a state with an unknown value by
serial_console_setup. And initialization fails.

This is caused by the initialization by sci_console_init.
This function does not seem to be necessary for the present sh-sci driver.

Signed-off-by: Nobuhiro Iwamatsu 
Signed-off-by: Paul Mundt

serial: sh-sci: prevent setup of uninitialized serial console

2011-03-31T05:33:22+00:00

Commit 906b17dc089f7fa87e37a9cfe6ee185efc90e0da introduced a condition
where the kernel will crash unless a earlyprintk parameter is specified.

Without this parameter, sci_console_init is called during early console
setup without any port being initialized, and the kernel crashes a
little bit later when uart_set_options attemps to invoke set_termios on a
port with an ops member equal to NULL.

This patch just checks in sci_console_init that the port is properly
initialized, and aborts the early console setup if it is not.

Signed-off-by: Alexandre Courbot 
Signed-off-by: Paul Mundt

serial: sh-sci: fix deadlock when resuming from S3 sleep

2011-03-04T06:57:10+00:00

S3 sleep invokes the shutdown callback of the sh-sci driver, which
suspends the clocks until they are reactivated by a call to startup.
However, before the latter is invoked, sci_set_termios may be called on
the port by uart_resume_port. In such cases it will endlessly wait for
the TEND bit to raise, which will never happen since the clocks are
disabled.

This patch ensures that clocks are enabled when ports registers are
manipulated within sci_set_termios.

Signed-off-by: Alexandre Courbot 
Signed-off-by: Paul Mundt