linux-stable.git/drivers/tty/serial/sh-sci.c, branch v3.16.40

serial: sh-sci: Remove cpufreq notifier to fix crash/deadlock

2016-04-30T22:06:11+00:00

commit ff1cab374ad98f4b9f408525ca9c08992b4ed784 upstream.

The BSP team noticed that there is spin/mutex lock issue on sh-sci when
CPUFREQ is used.  The issue is that the notifier function may call
mutex_lock() while the spinlock is held, which can lead to a BUG().
This may happen if CPUFREQ is changed while another CPU calls
clk_get_rate().

Taking the spinlock was added to the notifier function in commit
e552de2413edad1a ("sh-sci: add platform device private data"), to
protect the list of serial ports against modification during traversal.
At that time the Common Clock Framework didn't exist yet, and
clk_get_rate() just returned clk->rate without taking a mutex.
Note that since commit d535a2305facf9b4 ("serial: sh-sci: Require a
device per port mapping."), there's no longer a list of serial ports to
traverse, and taking the spinlock became superfluous.

To fix the issue, just remove the cpufreq notifier:
  1. The notifier doesn't work correctly: all it does is update the
     stored clock rate; it does not update the divider in the hardware.
     The divider will only be updated when calling sci_set_termios().
     I believe this was broken back in 2004, when the old
     drivers/char/sh-sci.c driver (where the notifier did update the
     divider) was replaced by drivers/serial/sh-sci.c (where the
     notifier just updated port->uartclk).
     Cfr. full-history-linux commits 6f8deaef2e9675d9 ("[PATCH] sh: port
     sh-sci driver to the new API") and 3f73fe878dc9210a ("[PATCH]
     Remove old sh-sci driver").
  2. On modern SoCs, the sh-sci parent clock rate is no longer related
     to the CPU clock rate anyway, so using a cpufreq notifier is
     futile.

Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Ben Hutchings

Merge tag 'tty-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty

2014-04-01T23:55:57+00:00

Pull tty/serial driver update from Greg KH:
 "Here's the big tty/serial driver update for 3.15-rc1.

  Nothing major, a number of serial driver updates and a few tty core
  fixes as well.

  All have been in linux-next for a while"

* tag 'tty-3.15-rc1' of git://git.kernel.org/pub/scm/linux/kernel/git/gregkh/tty: (71 commits)
  tty/serial: omap: empty the RX FIFO at the end of half-duplex TX
  tty/serial: omap: fix RX interrupt enable/disable in half-duplex TX
  serial: sh-sci: Neaten dev_ uses
  serial: sh-sci: Replace hardcoded 3 by UART_PM_STATE_OFF
  serial: sh-sci: Add more register documentation
  serial: sh-sci: Remove useless casts
  serial: sh-sci: Replace printk() by pr_*()
  serial_core: Avoid NULL pointer dereference in uart_close()
  serial_core: Get a reference for port->tty in uart_remove_one_port()
  serial: clps711x: Give a chance to perform useful tasks during wait loop
  serial_core: Grammar s/ports/port's/
  serial_core: Spelling s/contro/control/
  serial: efm32: properly namespace location property
  serial: max310x: Add missing #include 
  synclink: fix info leak in ioctl
  serial: 8250: Clean up the locking for -rt
  serial: 8250_pci: change BayTrail default uartclk
  serial: 8250_pci: more BayTrail error-free bauds
  serial: sh-sci: Add missing call to uart_remove_one_port() in failure path
  serial_core: Unregister console in uart_remove_one_port()
  ...

cpufreq: remove unused notifier: CPUFREQ_{SUSPENDCHANGE|RESUMECHANGE}

2014-03-19T13:10:24+00:00

Two cpufreq notifiers CPUFREQ_RESUMECHANGE and CPUFREQ_SUSPENDCHANGE have
not been used for some time, so remove them to clean up code a bit.

Signed-off-by: Viresh Kumar 
Reviewed-by: Srivatsa S. Bhat 
[rjw: Changelog]
Signed-off-by: Rafael J. Wysocki

serial: sh-sci: Neaten dev_ uses

2014-03-17T23:20:49+00:00

Add missing newlines and coalesce formats.
Realign arguments.

Signed-off-by: Joe Perches 
Acked-by: Geert Uytterhoeven 
Acked-by: Simon Horman 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Replace hardcoded 3 by UART_PM_STATE_OFF

2014-03-17T23:20:49+00:00

Signed-off-by: Geert Uytterhoeven 
Acked-by: Simon Horman 
Acked-by: Laurent Pinchart 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Add more register documentation

2014-03-17T23:20:49+00:00

Signed-off-by: Geert Uytterhoeven 
Acked-by: Simon Horman 
Acked-by: Laurent Pinchart 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Remove useless casts

2014-03-17T23:20:49+00:00

Signed-off-by: Geert Uytterhoeven 
Acked-by: Simon Horman 
Acked-by: Laurent Pinchart 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Replace printk() by pr_*()

2014-03-17T23:20:49+00:00

Make banner const while we're at it

Signed-off-by: Geert Uytterhoeven 
Acked-by: Simon Horman 
Acked-by: Laurent Pinchart 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Add missing call to uart_remove_one_port() in failure path

2014-03-01T00:39:38+00:00

If cpufreq_register_notifier() fails, we have to remove the port added by
sci_probe_single(), which is not done by sci_cleanup_single().

Else the serial port stays active from the point of view of the serial
subsystem, and it may crash when userspace getty is started, or when the
loadable driver module is unloaded.

This was introduced by commit 6dae14216c85eea13db7b12c469475c5d30e5499
("serial: sh-sci: Fix probe error paths").

Signed-off-by: Geert Uytterhoeven 
Signed-off-by: Greg Kroah-Hartman

serial: sh-sci: Fix cast warning

2014-02-13T17:17:31+00:00

Fix the following compile warning about cast to pointer from
integer of different size.

drivers/tty/serial/sh-sci.c:2021:19: warning: cast to pointer from integer of different size [-Wint-to-pointer-cast]

Signed-off-by: Jingoo Han 
Acked-by: Laurent Pinchart 
Signed-off-by: Greg Kroah-Hartman