2015-02-16 0:43 GMT+01:00 Andreas F?rber [off-list ref]:

Am 12.02.2015 um 18:45 schrieb Maxime Coquelin:

quoted

This patch adds clocksource support for ARMv7-M's System timer,
also known as SysTick.

Signed-off-by: Maxime Coquelin <mcoquelin.stm32@gmail.com>
---
 .../devicetree/bindings/arm/system_timer.txt       | 15 +++++
 drivers/clocksource/Kconfig                        |  7 ++
 drivers/clocksource/Makefile                       |  1 +
 drivers/clocksource/arm_system_timer.c             | 74 ++++++++++++++++++++++
 4 files changed, 97 insertions(+)
 create mode 100644 Documentation/devicetree/bindings/arm/system_timer.txt
 create mode 100644 drivers/clocksource/arm_system_timer.c

diff --git a/Documentation/devicetree/bindings/arm/system_timer.txt b/Documentation/devicetree/bindings/arm/system_timer.txt
new file mode 100644
index 0000000..35268b7
--- /dev/null
+++ b/Documentation/devicetree/bindings/arm/system_timer.txt

@@ -0,0 +1,15 @@
+* ARM System Timer
+
+ARMv7-M includes a system timer, known as SysTick. Current driver only
+implements the clocksource feature.
+
+Required properties:
+- compatible : Should be "arm,armv7m-systick"
+- reg             : The address range of the timer
+- clocks     : The input clock of the timer
+
+systick: system-timer {
+     compatible = "arm,armv7m-systick";
+     reg = <0xe000e010 0x10>;
+     clocks = <&clk_systick>;
+};

Binding documentation is supposed to go into its own patch:
https://git.kernel.org/cgit/linux/kernel/git/next/linux-next.git/tree/Documentation/devicetree/bindings/submitting-patches.txt

Ok, will change this in the v2.

...

I've used a SysTick based implementation on my stm32 branch myself, but
looking at efm32 I got the impression that it would be better to use one
of the 32-bit TIM2/TIM5 as clocksource and the other as clockevents?

Still this implementation will be handy to have, also for other targets.

My view is that we should use as much generic parts of the Cortex-M as possible.
Moreover, doing, that, we can keep one more IP instance under reset
with associated clock gated,
and so maybe reduce the power consumption a little (I haven't done any
measurements)

Do you see a case where it could be better to use the STM32 timers?


Thanks,
Maxime

Regards,
Andreas

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