Re: [PATCH] clocksource: tegra: wrap arch/arm-specific sections in CONFIG_ARM

[Thierry Reding <thierry.reding-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

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On Fri, Jan 09, 2015 at 09:31:08AM +0100, Daniel Lezcano wrote:
> On 01/09/2015 03:09 AM, Paul Walmsley wrote:
> >Hello Daniel
> >
> >On Thu, 8 Jan 2015, Daniel Lezcano wrote:
> >
> >>On 12/09/2014 11:07 PM, Paul Walmsley wrote:
> >>>
> >>>Like several of the other files in drivers/clocksource,
> >>>tegra20_timer.c contains code that can only compile when CONFIG_ARM is
> >>>enabled.  This causes obvious problems when trying to compile this
> >>>code for NVIDIA ARM64-based SoCs, such as Tegra132.  The same timer IP
> >>>blocks exist, so it seems appropriate to provide support for them.
> >>>
> >>>So until we figure out a better way to partition this code, wrap the
> >>>delay_timer and persistent_clock support code with preprocessor tests
> >>>for CONFIG_ARM.
> >>>
> >>>  (The delay_timer code should not be needed at all on
> >>>ARM64 due to the presence of the ARMv8 architected timer.  The
> >>>persistent_clock support code could become important once power
> >>>management modes are implemented that turn off the CPU complex.)
> >>
> >>IIUC, the cpuidle driver is not yet ready, right ?
> >>
> >>If it is the case, this driver is not needed yet, no ?
> >
> >The point of the patch is to allow the hardware drivers selected by
> >CONFIG_ARCH_TEGRA to build for an arm64 kernel, just as they build for
> >32-bit ARM.
> >
> >There's nothing CPUIdle-specific about the patch - that is, this timer can
> >be selected as a clockevent and clocksource provider without the use of
> >CPUIdle - although low-power PM idle is likely to be a primary use-case.
> 
> What I meant is this timer is not needed for the moment.
> 
> >>Perhaps you can rework a bit this driver in the meantime to have a better fix
> >>than disabling the code with macros ?
> >
> >I'm happy to do that, but it would be nice to get the driver compiling
> >first for ARM64 :-)
> >
> >>Otherwise, please try at least to group the code into a minimal set of macros.
> >
> >So, would it be accurate to say that you would prefer a patch that changes
> >more lines of code, but minimizes preprocessor directives, to the current
> >patch?
> 
> Yes at least an attempt to factor out a bit the driver. Those #ifdef are
> like #if 0, which is a quick fix. I am not strongly against this patch, but
> it would be nice to take the opportunity to reorganize it a bit.

How about we do something like the attached patch instead for now. That
avoids any #ifdef'ery and still we don't attempt (and fail) to build the
driver on 64-bit ARM.

With that applied we can incrementally make the changes to untangle the
ARM-specific parts and when the driver can build on 64-bit ARM we simply
select TEGRA_TIMER via Kconfig.

Thierry

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From dccf6b8e0dcf5695eb29a8749406472e578b972e Mon Sep 17 00:00:00 2001
From: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
Date: Mon, 7 Jul 2014 15:26:30 +0200
Subject: [PATCH] clocksource: Build Tegra timer on 32-bit ARM only

Instead of directly using the ARCH_TEGRA Kconfig symbol to enable this
driver, add a new, non-user-visible Kconfig symbol (TEGRA_TIMER) which
can be selected by the various SoCs.

This is useful to disable building the driver on Tegra132 (64-bit ARM)
where it doesn't currently compile but also isn't needed (yet).

Signed-off-by: Thierry Reding <treding-DDmLM1+adcrQT0dZR+AlfA@public.gmane.org>
---
 arch/arm/mach-tegra/Kconfig  | 4 ++++
 drivers/clocksource/Kconfig  | 3 +++
 drivers/clocksource/Makefile | 2 +-
 3 files changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/arm/mach-tegra/Kconfig b/arch/arm/mach-tegra/Kconfig
index f87684e600c7..667a48e2f7d4 100644
--- a/arch/arm/mach-tegra/Kconfig
+++ b/arch/arm/mach-tegra/Kconfig
@@ -29,6 +29,7 @@ config ARCH_TEGRA_2x_SOC
 	select PINCTRL_TEGRA20
 	select PL310_ERRATA_727915 if CACHE_L2X0
 	select PL310_ERRATA_769419 if CACHE_L2X0
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra AP20 and T20 processors, based on the
 	  ARM CortexA9MP CPU and the ARM PL310 L2 cache controller
@@ -39,6 +40,7 @@ config ARCH_TEGRA_3x_SOC
 	select ARM_ERRATA_764369 if SMP
 	select PINCTRL_TEGRA30
 	select PL310_ERRATA_769419 if CACHE_L2X0
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T30 processor family, based on the
 	  ARM CortexA9MP CPU and the ARM PL310 L2 cache controller
@@ -49,6 +51,7 @@ config ARCH_TEGRA_114_SOC
 	select ARM_L1_CACHE_SHIFT_6
 	select HAVE_ARM_ARCH_TIMER
 	select PINCTRL_TEGRA114
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T114 processor family, based on the
 	  ARM CortexA15MP CPU
@@ -58,6 +61,7 @@ config ARCH_TEGRA_124_SOC
 	select ARM_L1_CACHE_SHIFT_6
 	select HAVE_ARM_ARCH_TIMER
 	select PINCTRL_TEGRA124
+	select TEGRA_TIMER
 	help
 	  Support for NVIDIA Tegra T124 processor family, based on the
 	  ARM CortexA15MP CPU
diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index fc01ec27d3c8..c062b6105d49 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -47,6 +47,9 @@ config SUN5I_HSTIMER
 	select CLKSRC_MMIO
 	bool
 
+config TEGRA_TIMER
+	bool
+
 config VT8500_TIMER
 	bool
 
diff --git a/drivers/clocksource/Makefile b/drivers/clocksource/Makefile
index 94d90b24b56b..ba9ebd868ec5 100644
--- a/drivers/clocksource/Makefile
+++ b/drivers/clocksource/Makefile
@@ -27,7 +27,7 @@ obj-$(CONFIG_ARCH_U300)		+= timer-u300.o
 obj-$(CONFIG_SUN4I_TIMER)	+= sun4i_timer.o
 obj-$(CONFIG_SUN5I_HSTIMER)	+= timer-sun5i.o
 obj-$(CONFIG_MESON6_TIMER)	+= meson6_timer.o
-obj-$(CONFIG_ARCH_TEGRA)	+= tegra20_timer.o
+obj-$(CONFIG_TEGRA_TIMER)	+= tegra20_timer.o
 obj-$(CONFIG_VT8500_TIMER)	+= vt8500_timer.o
 obj-$(CONFIG_ARCH_NSPIRE)	+= zevio-timer.o
 obj-$(CONFIG_ARCH_BCM_MOBILE)	+= bcm_kona_timer.o
-- 
2.1.3


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