linux-stable.git/drivers/tty/serial/sh-sci.c, branch v3.16.78

serial: sh-sci: disable DMA for uart_console

2019-10-05T15:19:40+00:00

commit 099506cbbc79c0bd52b19cb6b930f256dabc3950 upstream.

As noted in commit 84b40e3b57ee ("serial: 8250: omap: Disable DMA for
console UART"), UART console lines use low-level PIO only access functions
which will conflict with use of the line when DMA is enabled, e.g. when
the console line is also used for systemd messages. So disable DMA
support for UART console lines.

Reported-by: Michael Rodin 
Link: https://patchwork.kernel.org/patch/10929511/
Tested-by: Eugeniu Rosca 
Reviewed-by: Simon Horman 
Reviewed-by: Wolfram Sang 
Reviewed-by: Geert Uytterhoeven 
Signed-off-by: George G. Davis 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

serial: sh-sci: Fix setting SCSCR_TIE while transferring data

2019-08-13T11:38:47+00:00

commit 93bcefd4c6bad4c69dbc4edcd3fbf774b24d930d upstream.

We disable transmission interrupt (clear SCSCR_TIE) after all data has been transmitted
(if uart_circ_empty(xmit)). While transmitting, if the data is still in the tty buffer,
re-enable the SCSCR_TIE bit, which was done at sci_start_tx().
This is unnecessary processing, wasting CPU operation if the data transmission length is large.
And further, transmit end, FIFO empty bits disabling have also been performed in the step above.

Signed-off-by: Hoan Nguyen An 
Signed-off-by: Greg Kroah-Hartman 
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings

serial: sh-sci: prevent lockup on full TTY buffers

2018-06-16T21:22:29+00:00

commit 7842055bfce4bf0170d0f61df8b2add8399697be upstream.

When the TTY buffers fill up to the configured maximum, a system lockup
occurs:

[  598.820128] INFO: rcu_preempt detected stalls on CPUs/tasks:
[  598.825796]  0-...!: (1 GPs behind) idle=5a6/2/0 softirq=1974/1974 fqs=1
[  598.832577]  (detected by 3, t=62517 jiffies, g=296, c=295, q=126)
[  598.838755] Task dump for CPU 0:
[  598.841977] swapper/0       R  running task        0     0      0 0x00000022
[  598.849023] Call trace:
[  598.851476]  __switch_to+0x98/0xb0
[  598.854870]            (null)

This can be prevented by doing a dummy read of the RX data register.

This issue affects both HSCIF and SCIF ports. Reported for R-Car H3 ES2.0;
reproduced and fixed on H3 ES1.1. Probably affects other R-Car platforms
as well.

Reported-by: Yoshihiro Shimoda 
Signed-off-by: Ulrich Hecht 
Reviewed-by: Geert Uytterhoeven 
Tested-by: Nguyen Viet Dung 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

serial: sh-sci: Fix panic when serial console and DMA are enabled

2017-08-26T01:14:24+00:00

commit 3c9101766b502a0163d1d437fada5801cf616be2 upstream.

This patch fixes an issue that kernel panic happens when DMA is enabled
and we press enter key while the kernel booting on the serial console.

* An interrupt may occur after sci_request_irq().
* DMA transfer area is initialized by setup_timer() in sci_request_dma()
  and used in interrupt.

If an interrupt occurred between sci_request_irq() and setup_timer() in
sci_request_dma(), DMA transfer area has not been initialized yet.
So, this patch changes the order of sci_request_irq() and
sci_request_dma().

Fixes: 73a19e4c0301 ("serial: sh-sci: Add DMA support.")
Signed-off-by: Takatoshi Akiyama 
[Shimoda changes the commit log]
Signed-off-by: Yoshihiro Shimoda 
Signed-off-by: Greg Kroah-Hartman 
Signed-off-by: Ben Hutchings

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