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de4ed391ae
linux/drivers
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Helmut Grohne de4ed391ae serial: xuartps: reduce hardware TX race condition 
After sending data to the uart, the driver was waiting until the TX
FIFO was empty (for every single char written). After that, TX was
disabled by writing the original TX state to the status register. At
that time however, the state machine could still be shifting
characters. Not waiting can result in strange hardware states,
especially when coupled with calls to cdns_uart_set_termios, whose
symptom generally is garbage characters being received from uart or a
hang.

According to UG585, the TACTIVE bit of the channel status register
indicates the shifter operation and we should be waiting for that bit
to clear.

Sending characters does not require the TX FIFO to be empty, but merely
to not be full. So cdns_uart_console_putchar is updated accordingly.

During tests with an instrumented kernel and an oscilloscope, we could
determine that the chance of a race is reduced by this patch. It is not
removed entirely. On the oscilloscope, one can see that disabling the
transmitter early can result in the transmission hanging in the middle
of a character for a tiny duration. This hiccup is enough to
desynchronize with a remote device for a sequence of characters until a
data bit doesn't match the start or stop bits anymore.

Link: https://www.spinics.net/lists/linux-serial/msg23156.html
Link: https://www.spinics.net/lists/linux-serial/msg26139.html
Signed-off-by: Helmut Grohne <h.grohne@intenta.de>
Acked-by: Sören Brinkmann <soren.brinkmann@xilinx.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
2018-06-28 21:23:44 +09:00
..
accessibility
acpi Merge branches 'acpi-soc' and 'acpi-processor' 2018-06-21 14:19:08 +02:00
amba Merge branch 'for-linus' of git://git.armlinux.org.uk/~rmk/linux-arm 2018-06-06 13:49:25 -07:00
android treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
ata treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
atm treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
auxdisplay treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
base Power management changes for 4.18-rc2 2018-06-22 05:57:36 +09:00
bcma dma-mapping updates for 4.18: 2018-06-04 10:58:12 -07:00
block for-linus-20180623 2018-06-24 06:33:54 +08:00
bluetooth bluetooth: hci_nokia: Don't include linux/unaligned/le_struct.h directly. 2018-06-17 08:38:55 +09:00
bus - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
cdrom treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
char Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-06-24 06:31:54 +08:00
clk docs: Fix some broken references 2018-06-15 18:10:01 -03:00
clocksource Merge branch 'timers-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2018-06-24 19:16:42 +08:00
connector Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
cpufreq cpufreq: intel_pstate: Fix scaling max/min limits with Turbo 3.0 2018-06-19 10:40:29 +02:00
cpuidle powerpc updates for 4.18 2018-06-07 10:23:33 -07:00
crypto Merge branch 'linus' of git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6 2018-06-24 06:31:54 +08:00
dax libnvdimm for 4.18 2018-06-08 17:21:52 -07:00
dca
devfreq treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
dio
dma fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
dma-buf
edac treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
eisa
extcon treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
firewire treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
firmware efi/libstub/tpm: Initialize efi_physical_addr_t vars to zero for mixed mode 2018-06-22 10:58:27 +02:00
fmc treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
fpga fpga: clarify that unregister functions also free 2018-05-25 18:23:56 +02:00
fsi
gpio treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
gpu Fixes for v4.18-rc2: 2018-06-22 11:03:43 +10:00
hid Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/hid 2018-06-20 16:42:39 +09:00
hsi
hv treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
hwmon hwmon: (nct6775) Fix loop limit 2018-06-16 16:40:36 -07:00
hwspinlock hwspinlock updates for v4.18 2018-06-11 12:09:19 -07:00
hwtracing treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
i2c Merge branch 'i2c/for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2018-06-14 16:21:46 +09:00
ide treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
idle
iio treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
infiniband 4.18-rc 2018-06-21 07:22:30 +09:00
input docs: Fix some broken references 2018-06-15 18:10:01 -03:00
iommu - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
ipack treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
irqchip irqchip/gic-v3-its: Fix reprogramming of redistributors on CPU hotplug 2018-06-22 14:22:02 +02:00
isdn treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
leds treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
lightnvm for-linus-20180623 2018-06-24 06:33:54 +08:00
macintosh powerpc updates for 4.18 2018-06-07 10:23:33 -07:00
mailbox treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
mcb
md docs: Fix some broken references 2018-06-15 18:10:01 -03:00
media Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
memory - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
memstick treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
message treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
mfd Merge branch 'i2c/for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2018-06-14 16:21:46 +09:00
misc Merge branch 'i2c/for-4.18' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux 2018-06-14 16:21:46 +09:00
mmc treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
mtd - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
mux
net Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net 2018-06-21 07:13:42 +09:00
nfc treewide: devm_kmalloc() -> devm_kmalloc_array() 2018-06-12 16:19:22 -07:00
ntb - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
nubus Char/Misc driver patches for 4.18-rc1 2018-06-05 16:20:22 -07:00
nvdimm Merge branch 'for-4.18/mcsafe' into libnvdimm-for-next 2018-06-08 15:16:44 -07:00
nvme nvme-pci: limit max IO size and segments to avoid high order allocations 2018-06-21 18:59:46 +02:00
nvmem treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
of - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
opp PM / OPP: Update voltage in case freq == old_freq 2018-06-19 15:53:32 +05:30
oprofile treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
parisc dma-mapping updates for 4.18: 2018-06-04 10:58:12 -07:00
parport docs: Fix some broken references 2018-06-15 18:10:01 -03:00
pci - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
pcmcia treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
perf drivers/bus: arm-cci: fix build warnings 2018-05-29 16:38:16 +01:00
phy Merge git://git.kernel.org/pub/scm/linux/kernel/git/davem/net-next 2018-06-06 18:39:49 -07:00
pinctrl pinctrl: mt7622: fix a kernel panic when pio don't work as EINT controller 2018-06-18 07:55:57 +02:00
platform fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
pnp media updates for v4.18-rc1 2018-06-07 12:34:37 -07:00
power treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
powercap treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
pps
ps3
ptp ptp: replace getnstimeofday64() with ktime_get_real_ts64() 2018-06-20 07:59:53 +09:00
pwm pwm: Changes for v4.18-rc1 2018-06-14 16:25:43 +09:00
rapidio treewide: Use array_size() in vmalloc() 2018-06-12 16:19:22 -07:00
ras
regulator treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
remoteproc treewide: use PHYS_ADDR_MAX to avoid type casting ULLONG_MAX 2018-06-15 07:55:25 +09:00
reset - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
rpmsg rpmsg: smd: do not use mananged resources for endpoints and channels 2018-06-04 12:35:03 -07:00
rtc - New Device Support 2018-06-11 07:20:17 -07:00
s390 Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/s390/linux 2018-06-19 07:44:51 +09:00
sbus fix a series of Documentation/ broken file name references 2018-06-15 18:10:01 -03:00
scsi for-linus-20180623 2018-06-24 06:33:54 +08:00
sfi
sh treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
siox
slimbus treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
sn
soc treewide: use PHYS_ADDR_MAX to avoid type casting ULLONG_MAX 2018-06-15 07:55:25 +09:00
soundwire docs: Fix more broken references 2018-06-15 18:11:26 -03:00
spi treewide: devm_kzalloc() -> devm_kcalloc() 2018-06-12 16:19:22 -07:00
spmi
ssb
staging media: v4l: fix broken video4linux docs locations 2018-06-15 18:10:01 -03:00
target treewide: Use array_size() in vzalloc() 2018-06-12 16:19:22 -07:00
tc
tee
thermal - Error path bug fix for overflow tests (Dan) 2018-06-12 18:28:00 -07:00
thunderbolt
tty serial: xuartps: reduce hardware TX race condition 2018-06-28 21:23:44 +09:00
uio treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
usb vfs/y2038: inode timestamps conversion to timespec64 2018-06-15 07:31:07 +09:00
uwb treewide: kmalloc() -> kmalloc_array() 2018-06-12 16:19:22 -07:00
vfio VFIO updates for v4.18 2018-06-12 13:11:26 -07:00
vhost virtio, vhost: features, fixes 2018-06-16 06:35:02 +09:00
video Solve a series of broken links for files under Documentation: 2018-06-17 05:25:18 +09:00
virt treewide: kzalloc() -> kcalloc() 2018-06-12 16:19:22 -07:00
virtio virtio, vhost: features, fixes 2018-06-16 06:35:02 +09:00
visorbus
vlynq
vme
w1 Char/Misc driver patches for 4.18-rc1 2018-06-05 16:20:22 -07:00
watchdog MIPS changes for 4.18 2018-06-12 12:56:02 -07:00
xen xen: fixes for 4.18-rc2 2018-06-23 20:44:11 +08:00
zorro - Introduce arithmetic overflow test helper functions (Rasmus) 2018-06-06 17:27:14 -07:00
Kconfig
Makefile