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

From: Daniel Lezcano
Date: Fri Jan 09 2015 - 08:38:53 EST

On 01/09/2015 02:33 PM, Thierry Reding wrote:
On Fri, Jan 09, 2015 at 02:24:24PM +0100, Daniel Lezcano wrote:
On 01/09/2015 01:21 PM, Thierry Reding wrote:
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.

Yes, that is exactly what I was thinking about after sending the previous
email. And by this way, you also fixed the Kconfig option selection logic.

Great. Will you give your Acked-by so that I can take that patch through
the Tegra tree to resolve the build dependency?

Acked-by: Daniel Lezcano <daniel.lezcano@xxxxxxxxxx>


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