<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-stable.git/drivers/clocksource/Kconfig, branch linux-3.19.y</title>
<subtitle>Linux kernel stable tree</subtitle>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/'/>
<entry>
<title>Merge branch 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus</title>
<updated>2014-12-12T01:56:37+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-12-12T01:56:37+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=c0222ac086669a631814bbf857f8c8023452a4d7'/>
<id>c0222ac086669a631814bbf857f8c8023452a4d7</id>
<content type='text'>
Pull MIPS updates from Ralf Baechle:
 "This is an unusually large pull request for MIPS - in parts because
  lots of patches missed the 3.18 deadline but primarily because some
  folks opened the flood gates.

   - Retire the MIPS-specific phys_t with the generic phys_addr_t.
   - Improvments for the backtrace code used by oprofile.
   - Better backtraces on SMP systems.
   - Cleanups for the Octeon platform code.
   - Cleanups and fixes for the Loongson platform code.
   - Cleanups and fixes to the firmware library.
   - Switch ATH79 platform to use the firmware library.
   - Grand overhault to the SEAD3 and Malta interrupt code.
   - Move the GIC interrupt code to drivers/irqchip
   - Lots of GIC cleanups and updates to the GIC code to use modern IRQ
     infrastructures and features of the kernel.
   - OF documentation updates for the GIC bindings
   - Move GIC clocksource driver to drivers/clocksource
   - Merge GIC clocksource driver with clockevent driver.
   - Further updates to bring the GIC clocksource driver up to date.
   - R3000 TLB code cleanups
   - Improvments to the Loongson 3 platform code.
   - Convert pr_warning to pr_warn.
   - Merge a bunch of small lantiq and ralink fixes that have been
     staged/lingering inside the openwrt tree for a while.
   - Update archhelp for IP22/IP32
   - Fix a number of issues for Loongson 1B.
   - New clocksource and clockevent driver for Loongson 1B.
   - Further work on clk handling for Loongson 1B.
   - Platform work for Broadcom BMIPS.
   - Error handling cleanups for TurboChannel.
   - Fixes and optimization to the microMIPS support.
   - Option to disable the FTLB.
   - Dump more relevant information on machine check exception
   - Change binfmt to allow arch to examine PT_*PROC headers
   - Support for new style FPU register model in O32
   - VDSO randomization.
   - BCM47xx cleanups
   - BCM47xx reimplement the way the kernel accesses NVRAM information.
   - Random cleanups
   - Add support for ATH25 platforms
   - Remove pointless locking code in some PCI platforms.
   - Some improvments to EVA support
   - Minor Alchemy cleanup"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (185 commits)
  MIPS: Add MFHC0 and MTHC0 instructions to uasm.
  MIPS: Cosmetic cleanups of page table headers.
  MIPS: Add CP0 macros for extended EntryLo registers
  MIPS: Remove now unused definition of phys_t.
  MIPS: Replace use of phys_t with phys_addr_t.
  MIPS: Replace MIPS-specific 64BIT_PHYS_ADDR with generic PHYS_ADDR_T_64BIT
  PCMCIA: Alchemy Don't select 64BIT_PHYS_ADDR in Kconfig.
  MIPS: lib: memset: Clean up some MIPS{EL,EB} ifdefery
  MIPS: iomap: Use __mem_{read,write}{b,w,l} for MMIO
  MIPS: &lt;asm/types.h&gt; fix indentation.
  MAINTAINERS: Add entry for BMIPS multiplatform kernel
  MIPS: Enable VDSO randomization
  MIPS: Remove a temporary hack for debugging cache flushes in SMTC configuration
  MIPS: Remove declaration of obsolete arch_init_clk_ops()
  MIPS: atomic.h: Reformat to fit in 79 columns
  MIPS: Apply `.insn' to fixup labels throughout
  MIPS: Fix microMIPS LL/SC immediate offsets
  MIPS: Kconfig: Only allow 32-bit microMIPS builds
  MIPS: signal.c: Fix an invalid cast in ISA mode bit handling
  MIPS: mm: Only build one microassembler that is suitable
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull MIPS updates from Ralf Baechle:
 "This is an unusually large pull request for MIPS - in parts because
  lots of patches missed the 3.18 deadline but primarily because some
  folks opened the flood gates.

   - Retire the MIPS-specific phys_t with the generic phys_addr_t.
   - Improvments for the backtrace code used by oprofile.
   - Better backtraces on SMP systems.
   - Cleanups for the Octeon platform code.
   - Cleanups and fixes for the Loongson platform code.
   - Cleanups and fixes to the firmware library.
   - Switch ATH79 platform to use the firmware library.
   - Grand overhault to the SEAD3 and Malta interrupt code.
   - Move the GIC interrupt code to drivers/irqchip
   - Lots of GIC cleanups and updates to the GIC code to use modern IRQ
     infrastructures and features of the kernel.
   - OF documentation updates for the GIC bindings
   - Move GIC clocksource driver to drivers/clocksource
   - Merge GIC clocksource driver with clockevent driver.
   - Further updates to bring the GIC clocksource driver up to date.
   - R3000 TLB code cleanups
   - Improvments to the Loongson 3 platform code.
   - Convert pr_warning to pr_warn.
   - Merge a bunch of small lantiq and ralink fixes that have been
     staged/lingering inside the openwrt tree for a while.
   - Update archhelp for IP22/IP32
   - Fix a number of issues for Loongson 1B.
   - New clocksource and clockevent driver for Loongson 1B.
   - Further work on clk handling for Loongson 1B.
   - Platform work for Broadcom BMIPS.
   - Error handling cleanups for TurboChannel.
   - Fixes and optimization to the microMIPS support.
   - Option to disable the FTLB.
   - Dump more relevant information on machine check exception
   - Change binfmt to allow arch to examine PT_*PROC headers
   - Support for new style FPU register model in O32
   - VDSO randomization.
   - BCM47xx cleanups
   - BCM47xx reimplement the way the kernel accesses NVRAM information.
   - Random cleanups
   - Add support for ATH25 platforms
   - Remove pointless locking code in some PCI platforms.
   - Some improvments to EVA support
   - Minor Alchemy cleanup"

* 'upstream' of git://git.linux-mips.org/pub/scm/ralf/upstream-linus: (185 commits)
  MIPS: Add MFHC0 and MTHC0 instructions to uasm.
  MIPS: Cosmetic cleanups of page table headers.
  MIPS: Add CP0 macros for extended EntryLo registers
  MIPS: Remove now unused definition of phys_t.
  MIPS: Replace use of phys_t with phys_addr_t.
  MIPS: Replace MIPS-specific 64BIT_PHYS_ADDR with generic PHYS_ADDR_T_64BIT
  PCMCIA: Alchemy Don't select 64BIT_PHYS_ADDR in Kconfig.
  MIPS: lib: memset: Clean up some MIPS{EL,EB} ifdefery
  MIPS: iomap: Use __mem_{read,write}{b,w,l} for MMIO
  MIPS: &lt;asm/types.h&gt; fix indentation.
  MAINTAINERS: Add entry for BMIPS multiplatform kernel
  MIPS: Enable VDSO randomization
  MIPS: Remove a temporary hack for debugging cache flushes in SMTC configuration
  MIPS: Remove declaration of obsolete arch_init_clk_ops()
  MIPS: atomic.h: Reformat to fit in 79 columns
  MIPS: Apply `.insn' to fixup labels throughout
  MIPS: Fix microMIPS LL/SC immediate offsets
  MIPS: Kconfig: Only allow 32-bit microMIPS builds
  MIPS: signal.c: Fix an invalid cast in ISA mode bit handling
  MIPS: mm: Only build one microassembler that is suitable
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>clocksource: mips-gic: Add device-tree support</title>
<updated>2014-11-24T06:45:30+00:00</updated>
<author>
<name>Andrew Bresticker</name>
<email>abrestic@chromium.org</email>
</author>
<published>2014-11-12T19:43:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e12aa828ff42bae894e4eb7350d4dbf46eb19084'/>
<id>e12aa828ff42bae894e4eb7350d4dbf46eb19084</id>
<content type='text'>
Parse the GIC timer frequency and interrupt from the device-tree.

Signed-off-by: Andrew Bresticker &lt;abrestic@chromium.org&gt;
Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Cc: Rob Herring &lt;robh+dt@kernel.org&gt;
Cc: Pawel Moll &lt;pawel.moll@arm.com&gt;
Cc: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Ian Campbell &lt;ijc+devicetree@hellion.org.uk&gt;
Cc: Kumar Gala &lt;galak@codeaurora.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Jason Cooper &lt;jason@lakedaemon.net&gt;
Cc: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Cc: John Crispin &lt;blogic@openwrt.org&gt;
Cc: David Daney &lt;ddaney.cavm@gmail.com&gt;
Cc: Qais Yousef &lt;qais.yousef@imgtec.com&gt;
Cc: James Hogan &lt;james.hogan@imgtec.com&gt;
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8421/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Parse the GIC timer frequency and interrupt from the device-tree.

Signed-off-by: Andrew Bresticker &lt;abrestic@chromium.org&gt;
Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Cc: Rob Herring &lt;robh+dt@kernel.org&gt;
Cc: Pawel Moll &lt;pawel.moll@arm.com&gt;
Cc: Mark Rutland &lt;mark.rutland@arm.com&gt;
Cc: Ian Campbell &lt;ijc+devicetree@hellion.org.uk&gt;
Cc: Kumar Gala &lt;galak@codeaurora.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Jason Cooper &lt;jason@lakedaemon.net&gt;
Cc: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Cc: John Crispin &lt;blogic@openwrt.org&gt;
Cc: David Daney &lt;ddaney.cavm@gmail.com&gt;
Cc: Qais Yousef &lt;qais.yousef@imgtec.com&gt;
Cc: James Hogan &lt;james.hogan@imgtec.com&gt;
Cc: linux-mips@linux-mips.org
Cc: devicetree@vger.kernel.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8421/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>MIPS: Move GIC clocksource driver to drivers/clocksource/</title>
<updated>2014-11-24T06:45:14+00:00</updated>
<author>
<name>Andrew Bresticker</name>
<email>abrestic@chromium.org</email>
</author>
<published>2014-10-20T19:03:58+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=fa5635a277171021d364f6a3fab4addce8f358d2'/>
<id>fa5635a277171021d364f6a3fab4addce8f358d2</id>
<content type='text'>
Move the GIC clocksource driver to drivers/clocksource/mips-gic-timer.c.

Signed-off-by: Andrew Bresticker &lt;abrestic@chromium.org&gt;
Cc: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Jason Cooper &lt;jason@lakedaemon.net&gt;
Cc: Paul Burton &lt;paul.burton@imgtec.com&gt;
Cc: Qais Yousef &lt;qais.yousef@imgtec.com&gt;
Cc: John Crispin &lt;blogic@openwrt.org&gt;
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8133/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Move the GIC clocksource driver to drivers/clocksource/mips-gic-timer.c.

Signed-off-by: Andrew Bresticker &lt;abrestic@chromium.org&gt;
Cc: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Cc: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Cc: Jason Cooper &lt;jason@lakedaemon.net&gt;
Cc: Paul Burton &lt;paul.burton@imgtec.com&gt;
Cc: Qais Yousef &lt;qais.yousef@imgtec.com&gt;
Cc: John Crispin &lt;blogic@openwrt.org&gt;
Cc: linux-mips@linux-mips.org
Cc: linux-kernel@vger.kernel.org
Patchwork: https://patchwork.linux-mips.org/patch/8133/
Signed-off-by: Ralf Baechle &lt;ralf@linux-mips.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>clocksource: meson6: Select CLKSRC_MMIO</title>
<updated>2014-11-18T15:41:20+00:00</updated>
<author>
<name>Beniamino Galvani</name>
<email>b.galvani@gmail.com</email>
</author>
<published>2014-11-18T15:41:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=7b6b0a455d98c7a314278e0fdca25ec6395a502a'/>
<id>7b6b0a455d98c7a314278e0fdca25ec6395a502a</id>
<content type='text'>
Select CLKSRC_MMIO when the meson6_timer driver is enabled since it
depends on clocksource MMIO functions.

Signed-off-by: Beniamino Galvani &lt;b.galvani@gmail.com&gt;
Signed-off-by: Carlo Caione &lt;carlo@caione.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Select CLKSRC_MMIO when the meson6_timer driver is enabled since it
depends on clocksource MMIO functions.

Signed-off-by: Beniamino Galvani &lt;b.galvani@gmail.com&gt;
Signed-off-by: Carlo Caione &lt;carlo@caione.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip</title>
<updated>2014-10-09T10:35:05+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-10-09T10:35:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=47137c6ba1bcde30215795f9594cea770946456b'/>
<id>47137c6ba1bcde30215795f9594cea770946456b</id>
<content type='text'>
Pull timer updates from Thomas Gleixner:
 "Nothing really exciting this time:

   - a few fixlets in the NOHZ code

   - a new ARM SoC timer abomination.  One should expect that we have
     enough of them already, but they insist on inventing new ones.

   - the usual bunch of ARM SoC timer updates.  That feels like herding
     cats"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource: arm_arch_timer: Consolidate arch_timer_evtstrm_enable
  clocksource: arm_arch_timer: Enable counter access for 32-bit ARM
  clocksource: arm_arch_timer: Change clocksource name if CP15 unavailable
  clocksource: sirf: Disable counter before re-setting it
  clocksource: cadence_ttc: Add support for 32bit mode
  clocksource: tcb_clksrc: Sanitize IRQ request
  clocksource: arm_arch_timer: Discard unavailable timers correctly
  clocksource: vf_pit_timer: Support shutdown mode
  ARM: meson6: clocksource: Add Meson6 timer support
  ARM: meson: documentation: Add timer documentation
  clocksource: sh_tmu: Document r8a7779 binding
  clocksource: sh_mtu2: Document r7s72100 binding
  clocksource: sh_cmt: Document SoC specific bindings
  timerfd: Remove an always true check
  nohz: Avoid tick's double reprogramming in highres mode
  nohz: Fix spurious periodic tick behaviour in low-res dynticks mode
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull timer updates from Thomas Gleixner:
 "Nothing really exciting this time:

   - a few fixlets in the NOHZ code

   - a new ARM SoC timer abomination.  One should expect that we have
     enough of them already, but they insist on inventing new ones.

   - the usual bunch of ARM SoC timer updates.  That feels like herding
     cats"

* 'timers-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip:
  clocksource: arm_arch_timer: Consolidate arch_timer_evtstrm_enable
  clocksource: arm_arch_timer: Enable counter access for 32-bit ARM
  clocksource: arm_arch_timer: Change clocksource name if CP15 unavailable
  clocksource: sirf: Disable counter before re-setting it
  clocksource: cadence_ttc: Add support for 32bit mode
  clocksource: tcb_clksrc: Sanitize IRQ request
  clocksource: arm_arch_timer: Discard unavailable timers correctly
  clocksource: vf_pit_timer: Support shutdown mode
  ARM: meson6: clocksource: Add Meson6 timer support
  ARM: meson: documentation: Add timer documentation
  clocksource: sh_tmu: Document r8a7779 binding
  clocksource: sh_mtu2: Document r7s72100 binding
  clocksource: sh_cmt: Document SoC specific bindings
  timerfd: Remove an always true check
  nohz: Avoid tick's double reprogramming in highres mode
  nohz: Fix spurious periodic tick behaviour in low-res dynticks mode
</pre>
</div>
</content>
</entry>
<entry>
<title>ARM: meson6: clocksource: Add Meson6 timer support</title>
<updated>2014-09-28T23:50:05+00:00</updated>
<author>
<name>Carlo Caione</name>
<email>carlo@caione.org</email>
</author>
<published>2014-09-28T23:50:05+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=e4a6b378751fa8934c691816da1423e849059fad'/>
<id>e4a6b378751fa8934c691816da1423e849059fad</id>
<content type='text'>
Meson6 SoCs are equipped with 5 32-bit timers, called TIMER_A, TIMER_B,
TIMER_C, TIMER_D and TIMER_E.

The driver is providing clocksource support for the 32-bit counter using
TIMER_E. Clockevents are also supported using TIMER_A.

Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Carlo Caione &lt;carlo@caione.org&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Reviewed-by: Matthias Brugger &lt;matthias.bgg@gmail.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Meson6 SoCs are equipped with 5 32-bit timers, called TIMER_A, TIMER_B,
TIMER_C, TIMER_D and TIMER_E.

The driver is providing clocksource support for the 32-bit counter using
TIMER_E. Clockevents are also supported using TIMER_A.

Acked-by: Arnd Bergmann &lt;arnd@arndb.de&gt;
Signed-off-by: Carlo Caione &lt;carlo@caione.org&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Reviewed-by: Matthias Brugger &lt;matthias.bgg@gmail.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ARM: at91: PIT: Move the driver to drivers/clocksource</title>
<updated>2014-09-15T15:55:48+00:00</updated>
<author>
<name>Maxime Ripard</name>
<email>maxime.ripard@free-electrons.com</email>
</author>
<published>2014-09-02T16:12:35+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=b052ff30cd450c91a32e8e928979bca021462996'/>
<id>b052ff30cd450c91a32e8e928979bca021462996</id>
<content type='text'>
Now that we don't depend on anyting in the mach-at91 directory, we can just
move the driver to where it belongs.

Signed-off-by: Maxime Ripard &lt;maxime.ripard@free-electrons.com&gt;
Acked-by: Boris BREZILLON &lt;boris.brezillon@free-electrons.com&gt;
Acked-by: Alexandre Belloni &lt;alexandre.belloni@free-electrons.com&gt;
Acked-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Signed-off-by: Nicolas Ferre &lt;nicolas.ferre@atmel.com&gt;

Conflicts:
	arch/arm/mach-at91/Kconfig
	arch/arm/mach-at91/Makefile
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Now that we don't depend on anyting in the mach-at91 directory, we can just
move the driver to where it belongs.

Signed-off-by: Maxime Ripard &lt;maxime.ripard@free-electrons.com&gt;
Acked-by: Boris BREZILLON &lt;boris.brezillon@free-electrons.com&gt;
Acked-by: Alexandre Belloni &lt;alexandre.belloni@free-electrons.com&gt;
Acked-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
Signed-off-by: Nicolas Ferre &lt;nicolas.ferre@atmel.com&gt;

Conflicts:
	arch/arm/mach-at91/Kconfig
	arch/arm/mach-at91/Makefile
</pre>
</div>
</content>
</entry>
<entry>
<title>clocksource: exynos_mct: Only use 32-bits where possible</title>
<updated>2014-07-23T10:02:41+00:00</updated>
<author>
<name>Doug Anderson</name>
<email>dianders@chromium.org</email>
</author>
<published>2014-07-04T21:43:26+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=3252a646aa2cf706b2a26433a8bd9cb2e5dce410'/>
<id>3252a646aa2cf706b2a26433a8bd9cb2e5dce410</id>
<content type='text'>
The MCT has a nice 64-bit counter.  That means that we _can_ register
as a 64-bit clocksource and sched_clock.  ...but that doesn't mean we
should.

The 64-bit counter is read by reading two 32-bit registers.  That
means reading needs to be something like:
- Read upper half
- Read lower half
- Read upper half and confirm that it hasn't changed.

That wouldn't be terrible, but:
- THe MCT isn't very fast to access (hundreds of nanoseconds).
- The clocksource is queried _all the time_.

In total system profiles of real workloads on ChromeOS, we've seen
exynos_frc_read() taking 2% or more of CPU time even after optimizing
the 3 reads above to 2 (see below).

The MCT is clocked at ~24MHz on all known systems.  That means that
the 32-bit half of the counter rolls over every ~178 seconds.  This
inspired an optimization in ChromeOS to cache the upper half between
calls, moving 3 reads to 2.  ...but we can do better!  Having a 32-bit
timer that flips every 178 seconds is more than sufficient for Linux.
Let's just use the lower half of the MCT.

Times on 5420 to do 1000000 gettimeofday() calls from userspace:
* Original code:                      1323852 us
* ChromeOS cache upper half:          1173084 us
* ChromeOS + ldmia to optimize:       1045674 us
* Use lower 32-bit only (this code):  1014429 us

As you can see, the time used doesn't increase linearly with the
number of reads and we can make 64-bit work almost as fast as 32-bit
with a bit of assembly code.  But since there's no real gain for
64-bit, let's go with the simplest and fastest implementation.

Note: with this change roughly half the time for gettimeofday() is
spent in exynos_frc_read().  The rest is timer / system call overhead.

Also note: this patch disables the use of the MCT on ARM64 systems
until we've sorted out how to make "cycles_t" always 32-bit.  Really
ARM64 systems should be using arch timers anyway.

Signed-off-by: Doug Anderson &lt;dianders@chromium.org&gt;
Acked-by Vincent Guittot &lt;vincent.guittot@linaro.org&gt;
Signed-off-by: Kukjin Kim &lt;kgene.kim@samsung.com&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
The MCT has a nice 64-bit counter.  That means that we _can_ register
as a 64-bit clocksource and sched_clock.  ...but that doesn't mean we
should.

The 64-bit counter is read by reading two 32-bit registers.  That
means reading needs to be something like:
- Read upper half
- Read lower half
- Read upper half and confirm that it hasn't changed.

That wouldn't be terrible, but:
- THe MCT isn't very fast to access (hundreds of nanoseconds).
- The clocksource is queried _all the time_.

In total system profiles of real workloads on ChromeOS, we've seen
exynos_frc_read() taking 2% or more of CPU time even after optimizing
the 3 reads above to 2 (see below).

The MCT is clocked at ~24MHz on all known systems.  That means that
the 32-bit half of the counter rolls over every ~178 seconds.  This
inspired an optimization in ChromeOS to cache the upper half between
calls, moving 3 reads to 2.  ...but we can do better!  Having a 32-bit
timer that flips every 178 seconds is more than sufficient for Linux.
Let's just use the lower half of the MCT.

Times on 5420 to do 1000000 gettimeofday() calls from userspace:
* Original code:                      1323852 us
* ChromeOS cache upper half:          1173084 us
* ChromeOS + ldmia to optimize:       1045674 us
* Use lower 32-bit only (this code):  1014429 us

As you can see, the time used doesn't increase linearly with the
number of reads and we can make 64-bit work almost as fast as 32-bit
with a bit of assembly code.  But since there's no real gain for
64-bit, let's go with the simplest and fastest implementation.

Note: with this change roughly half the time for gettimeofday() is
spent in exynos_frc_read().  The rest is timer / system call overhead.

Also note: this patch disables the use of the MCT on ARM64 systems
until we've sorted out how to make "cycles_t" always 32-bit.  Really
ARM64 systems should be using arch timers anyway.

Signed-off-by: Doug Anderson &lt;dianders@chromium.org&gt;
Acked-by Vincent Guittot &lt;vincent.guittot@linaro.org&gt;
Signed-off-by: Kukjin Kim &lt;kgene.kim@samsung.com&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>clocksource: Kconfig: Let EM_TIMER_STI depend on HAS_IOMEM</title>
<updated>2014-07-23T10:02:33+00:00</updated>
<author>
<name>Chen Gang</name>
<email>gang.chen.5i5j@gmail.com</email>
</author>
<published>2014-07-08T12:39:40+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=40c96312dc3534d97c64d7d69acf1ea14ceff404'/>
<id>40c96312dc3534d97c64d7d69acf1ea14ceff404</id>
<content type='text'>
In 'em_sti.c', it will call devm_ioremap_resource() which need
HAS_IOMEM. So need let EM_TIMER_STI depend on HAS_IOMEM, too.

The related error (with allmodconfig under score):

  LD      init/built-in.o
em_sti.c:(.text.em_sti_probe+0x84): undefined reference to `devm_ioremap_resource'
make: *** [vmlinux] Error 1

Signed-off-by: Chen Gang &lt;gang.chen.5i5j@gmail.com&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In 'em_sti.c', it will call devm_ioremap_resource() which need
HAS_IOMEM. So need let EM_TIMER_STI depend on HAS_IOMEM, too.

The related error (with allmodconfig under score):

  LD      init/built-in.o
em_sti.c:(.text.em_sti_probe+0x84): undefined reference to `devm_ioremap_resource'
make: *** [vmlinux] Error 1

Signed-off-by: Chen Gang &lt;gang.chen.5i5j@gmail.com&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>clocksource: Add support for the Mediatek SoCs</title>
<updated>2014-07-23T10:02:31+00:00</updated>
<author>
<name>Matthias Brugger</name>
<email>matthias.bgg@gmail.com</email>
</author>
<published>2014-07-18T09:36:43+00:00</published>
<link rel='alternate' type='text/html' href='https://git.tavy.me/linux-stable.git/commit/?id=ecb3530dd59ddd5158bcc507d634e698130fd937'/>
<id>ecb3530dd59ddd5158bcc507d634e698130fd937</id>
<content type='text'>
This patch adds a clock source and clock event for the timer found
on the Mediatek SoCs.

The Mediatek General Purpose Timer block provides five 32 bit timers and
one 64 bit timer.

Two 32 bit timers are used by this driver:
TIMER1: clock events supporting periodic and oneshot events
TIMER2: clock source configured as a free running counter

The General Purpose Timer block can be run with two clocks. A 13 MHz system
clock and the RTC clock running at 32 KHz. This implementation uses the system
clock with no clock source divider.

The interrupts are shared between the different timers and have to be read back
from a register. We just enable one interrupt for the clock event. The clock
event timer is used by all cores.

Signed-off-by: Matthias Brugger &lt;matthias.bgg@gmail.com&gt;
Acked-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This patch adds a clock source and clock event for the timer found
on the Mediatek SoCs.

The Mediatek General Purpose Timer block provides five 32 bit timers and
one 64 bit timer.

Two 32 bit timers are used by this driver:
TIMER1: clock events supporting periodic and oneshot events
TIMER2: clock source configured as a free running counter

The General Purpose Timer block can be run with two clocks. A 13 MHz system
clock and the RTC clock running at 32 KHz. This implementation uses the system
clock with no clock source divider.

The interrupts are shared between the different timers and have to be read back
from a register. We just enable one interrupt for the clock event. The clock
event timer is used by all cores.

Signed-off-by: Matthias Brugger &lt;matthias.bgg@gmail.com&gt;
Acked-by: Thomas Gleixner &lt;tglx@linutronix.de&gt;
Signed-off-by: Daniel Lezcano &lt;daniel.lezcano@linaro.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
