linux-sg2042/Documentation
Mark Rutland 4155fc07fa Doc: dt: arch_timer: discourage clock-frequency use
The ARM Generic Timer (AKA the architected timer, arm_arch_timer)
features a CPU register (CNTFRQ) which firmware is intended to
initialize, and non-secure software can read to determine the frequency
of the timer. On CPUs with secure state, this register cannot be written
from non-secure states.

The firmware of early SoCs featuring the timer did not correctly
initialize CNTFRQ correctly on all CPUs, requiring the frequency to be
described in DT as a workaround. This workaround is not complete however
as it is exposed to all software in a privileged non-secure mode
(including guests running under a hypervisor). The firmware and DTs for
recent SoCs have followed the example set by these early SoCs.

This patch updates the arch timer binding documentation to make it
clearer that the use of the clock-frequency property is a poor
work-around. The MMIO generic timer binding is similarly updated, though
this is less of a concern as there is generally no need to expose the
MMIO timers to guest OSs.

Signed-off-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Acked-by: Marc Zyngier <marc.zyngier@arm.com>
Acked-by: Olof Johansson <olof@lixom.net>
Acked-by: Stephen Boyd <sboyd@codeaurora.org>
Cc: Rob Herring <robh+dt@kernel.org>
Cc: Will Deacon <will.deacon@arm.com>
Signed-off-by: Rob Herring <robh@kernel.org>
2015-04-16 09:08:45 -05:00
..
ABI platform-drivers-x86 for 3.20 2015-02-19 10:56:51 -08:00
DocBook KGDB/KDB New: 2015-02-20 15:13:29 -08:00
EDID
PCI
RCU
accounting
acpi
aoe
arm ARM: SoC platform changes 2015-02-17 09:27:54 -08:00
arm64
auxdisplay
backlight
blackfin Documentation: fix blackfin gptimers-example build errors 2015-01-28 12:07:58 -07:00
block
blockdev
bus-devices
cdrom
cgroups mm: memcontrol: use "max" instead of "infinity" in control knobs 2015-02-28 09:57:51 -08:00
connector
console
cpu-freq intel_pstate: Add num_pstates to sysfs 2015-01-30 01:52:17 +01:00
cpuidle
cris
crypto
development-process
device-mapper dm crypt: add 'submit_from_crypt_cpus' option 2015-02-16 11:11:15 -05:00
devicetree Doc: dt: arch_timer: discourage clock-frequency use 2015-04-16 09:08:45 -05:00
dmaengine Merge branch 'for-linus' of git://git.infradead.org/users/vkoul/slave-dma 2015-02-18 08:49:20 -08:00
driver-model Staging drivers patches for 3.20-rc1 2015-02-15 11:30:39 -08:00
dvb
early-userspace
extcon
fault-injection
fb
filesystems ocfs2: update web page + git tree in documentation 2015-02-28 09:57:50 -08:00
firmware_class
fmc
frv
gpio gpio: board.txt: Fix the gpio name example 2015-01-28 11:14:00 -07:00
hid
hwmon
i2c i2c: fix reference to functionality constants definition 2015-02-19 16:57:48 +01:00
i2o
ia64 virtual: Documentation: simplify and generalize paravirt_ops.txt 2015-02-13 17:15:44 +10:30
ide
infiniband
input Input: ALPS - move v7 packet info to Documentation and v6 packet info 2015-02-15 16:04:23 -08:00
ioctl
isdn
ja_JP
kbuild Merge branch 'misc' of git://git.kernel.org/pub/scm/linux/kernel/git/mmarek/kbuild 2015-02-19 10:31:37 -08:00
kdump
ko_KR
laptops
leds
locking Documentation changes for 3.20 2015-02-11 13:03:11 -08:00
m68k
memory-devices
metag
mic
mips
misc-devices Documentation/misc-devices/mei: Fix indentation of embedded code. 2015-01-29 12:56:20 -07:00
mmc
mn10300
mtd
namespaces
netlabel
networking Documentation changes for 3.20 2015-02-11 13:03:11 -08:00
nfc
nios2
parisc
pcmcia
phy
platform
power genirq / PM: describe IRQF_COND_SUSPEND 2015-03-06 01:28:14 +01:00
powerpc
pps
prctl
pti
ptp
rapidio
s390
scheduler doc: brief user documentation for completion 2015-01-30 11:19:25 -07:00
scsi
security
serial
sh
sound
spi
sysctl Merge branch 'akpm' (patches from Andrew) 2015-02-11 18:23:28 -08:00
target
thermal
timers
tpm
trace Char / Misc patches for 3.20-rc1 2015-02-15 10:48:44 -08:00
usb Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/jikos/trivial 2015-02-10 18:57:15 -08:00
vDSO
video4linux MODULE_DEVICE_TABLE: fix some callsites 2015-02-13 21:21:40 -08:00
virtual OK, this has the big virtio 1.0 implementation, as specified by OASIS. 2015-02-18 09:24:01 -08:00
vm mm:add KPF_ZERO_PAGE flag for /proc/kpageflags 2015-02-11 17:06:00 -08:00
w1
watchdog
wimax
x86 Merge branch 'x86-urgent-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip 2015-02-21 10:41:29 -08:00
xtensa
zh_CN
00-INDEX
BUG-HUNTING
Changes
CodeOfConflict Code of Conflict 2015-02-27 11:44:24 -08:00
CodingStyle CodingStyle: enable emacs display of trailing whitespace 2015-01-28 12:05:46 -07:00
DMA-API-HOWTO.txt
DMA-API.txt
DMA-ISA-LPC.txt
DMA-attributes.txt
HOWTO
IPMI.txt
IRQ-affinity.txt
IRQ-domain.txt
IRQ.txt
Intel-IOMMU.txt
Makefile
ManagementStyle
SAK.txt
SM501.txt
SecurityBugs
SubmitChecklist
SubmittingDrivers
SubmittingPatches Merge branch 'doc/sp-update' into docs-next 2015-01-29 13:11:58 -07:00
VGA-softcursor.txt
applying-patches.txt
assoc_array.txt
atomic_ops.txt
bad_memory.txt
basic_profiling.txt
bcache.txt
binfmt_misc.txt
braille-console.txt
bt8xxgpio.txt
btmrvl.txt
bus-virt-phys-mapping.txt
cachetlb.txt rmap: drop support of non-linear mappings 2015-02-10 14:30:31 -08:00
circular-buffers.txt
clk.txt clk: Add rate constraints to clocks 2015-02-02 14:23:42 -08:00
coccinelle.txt
cpu-hotplug.txt
cpu-load.txt
cputopology.txt
crc32.txt
dcdbas.txt
debugging-modules.txt
debugging-via-ohci1394.txt
dell_rbu.txt
devices.txt
digsig.txt
dma-buf-sharing.txt
dontdiff
dynamic-debug-howto.txt
edac.txt
efi-stub.txt
eisa.txt
email-clients.txt
flexible-arrays.txt
futex-requeue-pi.txt
gcov.txt
gdb-kernel-debugging.txt scripts/gdb: add basic documentation 2015-02-17 14:34:54 -08:00
highuid.txt
hsi.txt
hw_random.txt
hwspinlock.txt
init.txt
initrd.txt
intel_txt.txt
io-mapping.txt
io_ordering.txt
iostats.txt
irqflags-tracing.txt
isapnp.txt
java.txt
kasan.txt kasan: enable instrumentation of global variables 2015-02-13 21:21:42 -08:00
kernel-doc-nano-HOWTO.txt
kernel-docs.txt
kernel-parameters.txt TTY/Serial driver patches for 3.20-rc1 2015-02-15 11:37:02 -08:00
kernel-per-CPU-kthreads.txt
kmemcheck.txt
kmemleak.txt
kobject.txt
kprobes.txt Documentation: add description for FTRACE probe status 2015-02-04 16:05:44 -05:00
kref.txt
kselftest.txt
ldm.txt
local_ops.txt
lockup-watchdogs.txt
logo.gif
logo.txt
lzo.txt
magic-number.txt
mailbox.txt
md.txt
media-framework.txt
memory-barriers.txt
memory-hotplug.txt
module-signing.txt
mono.txt
nommu-mmap.txt
numastat.txt
oops-tracing.txt
padata.txt
parport-lowlevel.txt
parport.txt
percpu-rw-semaphore.txt
phy.txt
pi-futex.txt
pinctrl.txt
pnp.txt
preempt-locking.txt
printk-formats.txt
pwm.txt
ramoops.txt
rbtree.txt
remoteproc.txt
rfkill.txt
robust-futex-ABI.txt
robust-futexes.txt
rpmsg.txt
rtc.txt
serial-console.txt
sgi-ioc4.txt
smsc_ece1099.txt
sparse.txt
stable_api_nonsense.txt
stable_kernel_rules.txt
static-keys.txt
svga.txt
sysfs-rules.txt
sysrq.txt
this_cpu_ops.txt
unaligned-memory-access.txt
unicode.txt
unshare.txt
vfio.txt
vgaarbiter.txt
video-output.txt
vme_api.txt
volatile-considered-harmful.txt
workqueue.txt
xillybus.txt
xz.txt
zorro.txt