linux-kernel - Re: [PATCH v5 08/13] ARM: sunxi: Add initialization of CNTVOFF

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Date:   Wed, 4 Apr 2018 09:45:15 +0200
From:   Maxime Ripard <maxime.ripard@...tlin.com>
To:     Mylène Josserand <mylene.josserand@...tlin.com>
Cc:     linux@...linux.org.uk, wens@...e.org, marc.zyngier@....com,
        mark.rutland@....com, robh+dt@...nel.org,
        devicetree@...r.kernel.org, clabbe.montjoie@...il.com,
        quentin.schulz@...tlin.com, thomas.petazzoni@...tlin.com,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH v5 08/13] ARM: sunxi: Add initialization of CNTVOFF

On Tue, Apr 03, 2018 at 10:06:28PM +0200, Mylène Josserand wrote:
> Hello,
> 
> Thank you for the review.
> 
> On Tue, 3 Apr 2018 11:12:18 +0200
> Maxime Ripard <maxime.ripard@...tlin.com> wrote:
> 
> > On Tue, Apr 03, 2018 at 08:18:31AM +0200, Mylène Josserand wrote:
> > > Add the initialization of CNTVOFF for sun8i-a83t.
> > > 
> > > For boot CPU, Create a new machine that handles this
> > > function's call in an "init_early" callback.
> > > For secondary CPUs, add this function into secondary_startup
> > > assembly entry.
> > > 
> > > Signed-off-by: Mylène Josserand <mylene.josserand@...tlin.com>
> > > ---
> > >  arch/arm/mach-sunxi/headsmp.S |  1 +
> > >  arch/arm/mach-sunxi/sunxi.c   | 18 +++++++++++++++++-
> > >  2 files changed, 18 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/arch/arm/mach-sunxi/headsmp.S b/arch/arm/mach-sunxi/headsmp.S
> > > index 79890fbe5613..b586b7cf803a 100644
> > > --- a/arch/arm/mach-sunxi/headsmp.S
> > > +++ b/arch/arm/mach-sunxi/headsmp.S
> > > @@ -71,6 +71,7 @@ ENDPROC(sunxi_mc_smp_cluster_cache_enable)
> > >  
> > >  ENTRY(sunxi_mc_smp_secondary_startup)
> > >  	bl	sunxi_mc_smp_cluster_cache_enable
> > > +	bl	smp_init_cntvoff
> > >  	b	secondary_startup
> > >  ENDPROC(sunxi_mc_smp_secondary_startup)
> > >  
> > > diff --git a/arch/arm/mach-sunxi/sunxi.c b/arch/arm/mach-sunxi/sunxi.c
> > > index 5e9602ce1573..090784108c0a 100644
> > > --- a/arch/arm/mach-sunxi/sunxi.c
> > > +++ b/arch/arm/mach-sunxi/sunxi.c
> > > @@ -16,6 +16,7 @@
> > >  #include <linux/platform_device.h>
> > >  
> > >  #include <asm/mach/arch.h>
> > > +#include <asm/smp_cntvoff.h>
> > >  
> > >  static const char * const sunxi_board_dt_compat[] = {
> > >  	"allwinner,sun4i-a10",
> > > @@ -62,7 +63,6 @@ MACHINE_END
> > >  static const char * const sun8i_board_dt_compat[] = {
> > >  	"allwinner,sun8i-a23",
> > >  	"allwinner,sun8i-a33",
> > > -	"allwinner,sun8i-a83t",
> > >  	"allwinner,sun8i-h2-plus",
> > >  	"allwinner,sun8i-h3",
> > >  	"allwinner,sun8i-r40",
> > > @@ -75,6 +75,22 @@ DT_MACHINE_START(SUN8I_DT, "Allwinner sun8i Family")
> > >  	.dt_compat	= sun8i_board_dt_compat,
> > >  MACHINE_END
> > >  
> > > +void __init sun8i_cntvoff_init(void)
> > > +{
> > > +	smp_init_cntvoff();  
> > 
> > Can't this be moved to the SMP setup code?
> 
> I tried to put it in the first lines of "sunxi_mc_smp_init" function
> but it did not work. I tried to find some callbacks to have an
> early "init" and I only found the "init_early"'s one. There is probably
> another way to handle that so do not hesitate to tell me any ideas.

It's hard to say without more context about why it doesn't work. Have
you checked the order between early_initcall, the timer initialization
function and init_early?

> > > +}
> > > +
> > > +static const char * const sun8i_cntvoff_board_dt_compat[] = {
> > > +	"allwinner,sun8i-a83t",
> > > +	NULL,
> > > +};
> > > +
> > > +DT_MACHINE_START(SUN8I_CNTVOFF_DT, "Allwinner sun8i boards needing cntvoff")  
> > 
> > All of the SoCs need CNTVOFF, so that doesn't really make sense. Why
> > not just calling it for what it is: an A83t?
> 
> Sure, I will update it.

Looking back at that code, I guess you want to change also the
smp_init_cntvoff function. It's not really related to SMP either.

Maxime

-- 
Maxime Ripard, Bootlin (formerly Free Electrons)
Embedded Linux and Kernel engineering
https://bootlin.com

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