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

[Daniel Lezcano]

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.


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