[2/9] ARM64: get rid of arch_cpu_idle_prepare()

ARM and ARM64 are the only two architectures implementing
arch_cpu_idle_prepare() simply to call local_fiq_enable().

We have secondary_start_kernel() already calling local_fiq_enable() and
this is done a second time in arch_cpu_idle_prepare() in that case. And
enabling FIQs has nothing to do with idling the CPU to start with.

So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
at late_initcall time but this shouldn't make a difference in practice
given that FIQs are not currently used on ARM64.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
---
 arch/arm64/kernel/process.c | 5 -----
 arch/arm64/kernel/setup.c   | 7 +++++++
 2 files changed, 7 insertions(+), 5 deletions(-)

On 01/27/2014 07:08 AM, Nicolas Pitre wrote:
> ARM and ARM64 are the only two architectures implementing
> arch_cpu_idle_prepare() simply to call local_fiq_enable().
>
> We have secondary_start_kernel() already calling local_fiq_enable() and
> this is done a second time in arch_cpu_idle_prepare() in that case. And
> enabling FIQs has nothing to do with idling the CPU to start with.
>
> So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
> CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
> at late_initcall time but this shouldn't make a difference in practice
> given that FIQs are not currently used on ARM64.
>
> Signed-off-by: Nicolas Pitre <nico@linaro.org>

Reviewed-by: Daniel Lezcano <daniel.lezcano@linaro.org>

> ---
>   arch/arm64/kernel/process.c | 5 -----
>   arch/arm64/kernel/setup.c   | 7 +++++++
>   2 files changed, 7 insertions(+), 5 deletions(-)
>
> diff --git a/arch/arm64/kernel/process.c b/arch/arm64/kernel/process.c
> index de17c89985..f6c733da67 100644
> --- a/arch/arm64/kernel/process.c
> +++ b/arch/arm64/kernel/process.c
> @@ -84,11 +84,6 @@ EXPORT_SYMBOL_GPL(pm_power_off);
>   void (*arm_pm_restart)(enum reboot_mode reboot_mode, const char *cmd);
>   EXPORT_SYMBOL_GPL(arm_pm_restart);
>
> -void arch_cpu_idle_prepare(void)
> -{
> -	local_fiq_enable();
> -}
> -
>   /*
>    * This is our default idle handler.
>    */
> diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c
> index bd9bbd0e44..259557983a 100644
> --- a/arch/arm64/kernel/setup.c
> +++ b/arch/arm64/kernel/setup.c
> @@ -255,6 +255,13 @@ static int __init arm64_device_init(void)
>   }
>   arch_initcall(arm64_device_init);
>
> +static int __init init_fiq_boot_cpu(void)
> +{
> +	local_fiq_enable();
> +	return 0;
> +}
> +late_initcall(init_fiq_boot_cpu);
> +
>   static DEFINE_PER_CPU(struct cpu, cpu_data);
>
>   static int __init topology_init(void)
>

On Mon, Jan 27, 2014 at 06:08:17AM +0000, Nicolas Pitre wrote:
> ARM and ARM64 are the only two architectures implementing
> arch_cpu_idle_prepare() simply to call local_fiq_enable().
> 
> We have secondary_start_kernel() already calling local_fiq_enable() and
> this is done a second time in arch_cpu_idle_prepare() in that case. And
> enabling FIQs has nothing to do with idling the CPU to start with.
> 
> So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
> CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
> at late_initcall time but this shouldn't make a difference in practice
> given that FIQs are not currently used on ARM64.
> 
> Signed-off-by: Nicolas Pitre <nico@linaro.org>

For arm64, we could simply remove any reference to FIQs. I'm not aware
of anyone using them.

On Mon, 27 Jan 2014, Catalin Marinas wrote:

> On Mon, Jan 27, 2014 at 06:08:17AM +0000, Nicolas Pitre wrote:
> > ARM and ARM64 are the only two architectures implementing
> > arch_cpu_idle_prepare() simply to call local_fiq_enable().
> > 
> > We have secondary_start_kernel() already calling local_fiq_enable() and
> > this is done a second time in arch_cpu_idle_prepare() in that case. And
> > enabling FIQs has nothing to do with idling the CPU to start with.
> > 
> > So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
> > CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
> > at late_initcall time but this shouldn't make a difference in practice
> > given that FIQs are not currently used on ARM64.
> > 
> > Signed-off-by: Nicolas Pitre <nico@linaro.org>
> 
> For arm64, we could simply remove any reference to FIQs. I'm not aware
> of anyone using them.

OK. What if I sumply remove arch_cpu_idle_prepare() and let you do the 
remove the rest?

IMHO I'd simply remove local_fiq_{enable/disable}() from 
arm64/kernel/smp.c and leave the infrastructure in place in case someone 
needs it eventually.  In which case I could include that into my patch 
as well.


Nicolas

On Mon, Jan 27, 2014 at 03:51:02PM +0000, Nicolas Pitre wrote:
> On Mon, 27 Jan 2014, Catalin Marinas wrote:
> 
> > On Mon, Jan 27, 2014 at 06:08:17AM +0000, Nicolas Pitre wrote:
> > > ARM and ARM64 are the only two architectures implementing
> > > arch_cpu_idle_prepare() simply to call local_fiq_enable().
> > > 
> > > We have secondary_start_kernel() already calling local_fiq_enable() and
> > > this is done a second time in arch_cpu_idle_prepare() in that case. And
> > > enabling FIQs has nothing to do with idling the CPU to start with.
> > > 
> > > So let's introduce init_fiq_boot_cpu() to take care of FIQs on the boot
> > > CPU and remove arch_cpu_idle_prepare(). This is now done a bit earlier
> > > at late_initcall time but this shouldn't make a difference in practice
> > > given that FIQs are not currently used on ARM64.
> > > 
> > > Signed-off-by: Nicolas Pitre <nico@linaro.org>
> > 
> > For arm64, we could simply remove any reference to FIQs. I'm not aware
> > of anyone using them.
> 
> OK. What if I sumply remove arch_cpu_idle_prepare() and let you do the 
> remove the rest?
> 
> IMHO I'd simply remove local_fiq_{enable/disable}() from 
> arm64/kernel/smp.c and leave the infrastructure in place in case someone 
> needs it eventually.  In which case I could include that into my patch 
> as well.

Sounds good. We can keep the local_fiq_*() functions but remove about 4
calling sites (process.c and smp.c) until needed.

Thanks.