linux/drivers
Rajanikanth H.V 4fd0690bb0 serial: pl011: implement workaround for CTS clear event issue
Problem Observed:
- interrupt status is set by rising or falling edge on CTS line
- interrupt status is cleared on a .0. to .1. transition of the
  interrupt-clear register bit 1.
- interrupt-clear register is reset by hardware once the interrupt
  status is .0..
  Remark: It seems not possible to read this register back by the
  CPU though, but internally this register exists.
- when simultaneous set and reset event on the interrupt status
  happens, then the set-event has priority and the status remains
  .1.. As a result the interrupt-clear register is not reset to
  .0., and no new .0. to .1. transition can be detected on it when
  writing a .1. to it.
  This implies race condition, the clear must be performed at least
  one UARTCLK the riding edge of CTS RIS interrupt.

Fix:
  Instead of resetting UART as done in commit
  c16d51a32b
  "amba pl011: workaround for uart registers lockup" do the
  following:

  write .0. and then  .1. to the interrupt-clear register to make
  sure that this transition is detected. According to the datasheet
  writing a .0. does not have any effect, but actually it allows to
  reset the internal interrupt-clear register.

  Take into account:
  The .0. needs to last at least for one clk_uart clock period
  (~ 38 MHz, 26.08ns)

This way we can do away with the tasklet and keep only a tiny
fix triggered by the variant flag introduced in this patch.

Signed-off-by: Guillaume Jaunet <guillaume.jaunet@stericsson.com>
Signed-off-by: Christophe Arnal <christophe.arnal@stericsson.com>
Signed-off-by: Matthias Locher  <Matthias.Locher@stericsson.com>
Signed-off-by: Rajanikanth H.V <rajanikanth.hv@stericsson.com>
Reviewed-by: Srinidhi Kasagar <srinidhi.kasagar@stericsson.com>
Signed-off-by: Linus Walleij <linus.walleij@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2012-04-18 15:06:38 -07:00
..
accessibility
acpi Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2012-04-06 19:56:04 -07:00
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ata
atm Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
auxdisplay
base regmap: A couple of small fixes for 3.4 2012-04-07 09:56:00 -07:00
bcma
block Two fixes for regressions: 2012-04-06 17:54:53 -07:00
bluetooth Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
cdrom
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clocksource Merge branch 'for-linus' of git://git.linaro.org/people/rmk/linux-arm 2012-03-29 16:53:48 -07:00
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cpufreq ARM: SoC fixes for 3.4-rc2 2012-04-05 22:13:39 -07:00
cpuidle Merge branches 'idle-fix' and 'misc' into release 2012-04-06 21:48:59 -04:00
crypto
dca
devfreq ARM: global cleanups 2012-03-27 16:03:32 -07:00
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eisa
firewire Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
firmware
gpio gpio: tegra: Iterate over the correct number of banks 2012-04-04 13:13:18 -06:00
gpu Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
hid simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
hsi
hv
hwmon hwmon: (ad7314) Adds missing spi_dev initialization 2012-04-03 17:08:28 -07:00
hwspinlock
i2c Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
ide Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
idle simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
ieee802154
infiniband Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
input Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/dtor/input 2012-03-29 23:17:44 -07:00
iommu Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
isdn ISDN: remove uses of isdn_tty_revision 2012-04-10 09:01:14 -07:00
leds MFD changes for 3.4 2012-03-28 13:56:35 -07:00
lguest
macintosh Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
mca
md md/raid1,raid10: don't compare excess byte during consistency check. 2012-04-03 15:39:23 +10:00
media ARM: cleanups of io includes 2012-03-29 18:02:10 -07:00
memstick
message Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
mfd Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
misc Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
mmc mmc: use really long write timeout to deal with crappy cards 2012-04-05 20:32:34 -04:00
mtd Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
net TTY: hso, use tty from tty_port 2012-04-09 11:18:36 -07:00
nfc
nubus Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
of GPIO changes for v3.4 2012-03-28 14:08:46 -07:00
oprofile simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
parisc Disintegrate and delete asm/system.h 2012-03-28 15:58:21 -07:00
parport
pci Two fixes for regressions: 2012-04-06 17:54:53 -07:00
pcmcia Merge git://git.kernel.org/pub/scm/linux/kernel/git/brodo/pcmcia 2012-03-29 16:00:48 -07:00
pinctrl
platform Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2012-03-30 16:45:39 -07:00
pnp Merge branch 'release' of git://git.kernel.org/pub/scm/linux/kernel/git/lenb/linux 2012-03-30 16:45:39 -07:00
power Various small bugfixes and enhancements, plus two new drivers: 2012-03-30 16:09:02 -07:00
pps
ps3
ptp
rapidio
regulator regulator: Fixes for -rc1 2012-04-04 10:09:30 -07:00
remoteproc simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
rpmsg
rtc Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
s390 tty: add missing tty_port_tty_get() call to raw3215_wakeup 2012-04-17 13:55:43 -07:00
sbus Remove all #inclusions of asm/system.h 2012-03-28 18:30:03 +01:00
scsi Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
sfi
sh SuperH updates for 3.4 merge window 2012-03-30 00:09:17 -07:00
sn
spi Merge branch 'akpm' (Andrew's patch-bomb) 2012-04-05 15:30:34 -07:00
ssb
staging Documentation: remove references to /etc/modprobe.conf 2012-03-30 16:03:15 -07:00
target tcm_fc: Do not free tpg structure during wq allocation failure 2012-04-06 18:57:05 -07:00
tc
thermal
tty serial: pl011: implement workaround for CTS clear event issue 2012-04-18 15:06:38 -07:00
uio
usb TTY: usb/u_serial use close_wait from tty_port 2012-04-09 12:04:30 -07:00
uwb simple_open: automatically convert to simple_open() 2012-04-05 15:25:50 -07:00
vhost
video ARM: SoC fixes for 3.4-rc2 2012-04-05 22:13:39 -07:00
virt
virtio virtio-pci: switch to PM ops macro to initialise PM functions 2012-03-31 08:09:51 +05:30
vlynq
w1
watchdog ARM: cleanups of io includes 2012-03-29 18:02:10 -07:00
xen Two fixes for regressions: 2012-04-06 17:54:53 -07:00
zorro
Kconfig Merge branch 'for-next' of git://gitorious.org/kernel-hsi/kernel-hsi 2012-04-02 09:50:40 -07:00
Makefile Merge branch 'for-next' of git://gitorious.org/kernel-hsi/kernel-hsi 2012-04-02 09:50:40 -07:00