On 26/04/16 20:35, Grygorii Strashko wrote:
On 04/26/2016 07:02 PM, Liviu Dudau wrote:
On Tue, Apr 26, 2016 at 06:28:52PM +0300, Grygorii Strashko wrote:
Hi Grygorii,
First time I'm seeing this patch, so I have a few questions, mostly
related to the commit message:
Hm. You are in cc for RFC.
Sry, forgot to add link [1].
This patch intended to fix following cases:
- SoC-A has ARM GT, defines DT node for ARM GT and selects
ARM_GLOBAL_TIMER statically in Kconfig file. SoC-B has ARM GT and
defines DT node for ARM GT, but do not selects ARM_GLOBAL_TIMER
statically in Kconfig file. In case of multiplatform build ARM GT will
be implicitly enabled for SoC-B.
Well, SoC-B has the GT *and* the DT node, so what is the problem with
enabling it for SoC-B? If there are reasons not to use the Global Timer
on SoC-B, surely a better option would be to mark it in DT with status = "disabled";
This was rejected [2]. DT describes HW and if it is functional the status = "disabled"
is not good choice.
ARM GT can't be used as clocksource/sched_clock/clockevent when CPUFreq or
CPUIdle are enabled :(, and this is Linux specific functionality and
not HW description.
It sounds to me like the cleanest option might then be to address it
within the Linux-specific driver itself. How feasible would it be for
the GT driver to detect at runtime whether CPUfreq/idle will be used and
simply refuse to register as a clocksource if so? (I guess there are
probably horrible initialisation order issues, at least...)
Robin.
- There is no way to disable ARM GT without modifying Kconfig file,
once ARM_GLOBAL_TIMER is selected statically in Kconfig file.
What about disabling the DT node?
Not sure I properly understand the problem you are trying to solve here.
I'd like to have way to enable/disable ARM GT without modifying Kernel sources
(Kconfig specifically) which is now impossible.
Hence, fix above case by defining both HAVE_ARM_GLOBAL_TIMER and
ARM_GLOBAL_TIMER as recommended by 'Adding common features and make
the usage configurable' section in kconfig-language.txt. All places in
ARM folder where ARM_GLOBAL_TIMER was used now replaced on
HAVE_ARM_GLOBAL_TIMER.
I'm OK with the way you have changed ARM_GLOBAL_TIMER from a sticky config
option to a selectable one, but I would like more details on the problem
this was causing you.
The same HW (board) could be used with PM features enabled (power saving)
and disabled (-RT). Without this change it will require to have
and maintain two branches, but with it - just separate defconfig.
[1] http://lists.infradead.org/pipermail/linux-rockchip/2016-February/007159.html
[2] http://www.spinics.net/lists/devicetree/msg102918.html
Cc: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>
Cc: Florian Fainelli <f.fainelli@xxxxxxxxx>
Cc: Russell King <linux@xxxxxxxxxxxxxxxx>
Cc: Wei Xu <xuwei5@xxxxxxxxxxxxx>
Cc: Shawn Guo <shawnguo@xxxxxxxxxx>
Cc: Sascha Hauer <kernel@xxxxxxxxxxxxxx>
Cc: Srinivas Kandagatla <srinivas.kandagatla@xxxxxxxxx>
Cc: Maxime Coquelin <maxime.coquelin@xxxxxx>
Cc: Masahiro Yamada <yamada.masahiro@xxxxxxxxxxxxx>
Cc: Liviu Dudau <liviu.dudau@xxxxxxx>
Cc: Sudeep Holla <sudeep.holla@xxxxxxx>
Cc: Jun Nie <jun.nie@xxxxxxxxxx>
Cc: Michal Simek <michal.simek@xxxxxxxxxx>
Cc: Jesper Nilsson <jesper.nilsson@xxxxxxxx>
Cc: Lars Persson <lars.persson@xxxxxxxx>
Cc: Mike Looijmans <mike.looijmans@xxxxxxxx>
Acked-by: Sören Brinkmann <soren.brinkmann@xxxxxxxxxx>
Acked-by: Moritz Fischer <moritz.fischer@xxxxxxxxx>
Signed-off-by: Grygorii Strashko <grygorii.strashko@xxxxxx>
---
Changes is v1:
- updated mach-artpec
- rebased on top of tip: timers/core
commit: 86d3473 time: Introduce do_sys_settimeofday64()
arch/arm/mach-artpec/Kconfig | 2 +-
arch/arm/mach-bcm/Kconfig | 4 ++--
arch/arm/mach-hisi/Kconfig | 2 +-
arch/arm/mach-imx/Kconfig | 2 +-
arch/arm/mach-rockchip/Kconfig | 2 +-
arch/arm/mach-sti/Kconfig | 2 +-
arch/arm/mach-uniphier/Kconfig | 2 +-
arch/arm/mach-vexpress/Kconfig | 2 +-
arch/arm/mach-zx/Kconfig | 2 +-
arch/arm/mach-zynq/Kconfig | 2 +-
drivers/clocksource/Kconfig | 7 ++++++-
11 files changed, 17 insertions(+), 12 deletions(-)
diff --git a/arch/arm/mach-artpec/Kconfig b/arch/arm/mach-artpec/Kconfig
index 6cbe5a2..6cbca77 100644
--- a/arch/arm/mach-artpec/Kconfig
+++ b/arch/arm/mach-artpec/Kconfig
@@ -9,7 +9,7 @@ config MACH_ARTPEC6
depends on ARCH_MULTI_V7
select ARM_AMBA
select ARM_GIC
- select ARM_GLOBAL_TIMER
[...]
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