linux-kernel - Re: [PATCH v6 08/11] ARM: sun9i: smp: Add is

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Date:   Tue, 17 Apr 2018 15:57:07 +0800
From:   Chen-Yu Tsai <wens@...e.org>
To:     Maxime Ripard <maxime.ripard@...tlin.com>
Cc:     Mylène Josserand <mylene.josserand@...tlin.com>,
        Russell King <linux@...linux.org.uk>,
        Marc Zyngier <marc.zyngier@....com>,
        Mark Rutland <mark.rutland@....com>,
        Rob Herring <robh+dt@...nel.org>, Simon <horms@...ge.net.au>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Magnus Damm <magnus.damm@...il.com>,
        "open list:ARM/SHMOBILE ARM..." <linux-renesas-soc@...r.kernel.org>,
        devicetree <devicetree@...r.kernel.org>,
        LABBE Corentin <clabbe.montjoie@...il.com>,
        Quentin Schulz <quentin.schulz@...tlin.com>,
        Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
        linux-arm-kernel <linux-arm-kernel@...ts.infradead.org>,
        linux-kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v6 08/11] ARM: sun9i: smp: Add is_sun8i field

On Tue, Apr 17, 2018 at 3:52 PM, Maxime Ripard
<maxime.ripard@...tlin.com> wrote:
> Hi,
>
> On Mon, Apr 16, 2018 at 11:50:29PM +0200, Mylène Josserand wrote:
>> To prepare the support of sun8i-a83t, add a field in the smp_data
>> structure to know if we are on sun9i-a80 or sun8i-a83t.
>>
>> Add also a global variable to retrieve which architecture we are
>> having.
>>
>> Signed-off-by: Mylène Josserand <mylene.josserand@...tlin.com>
>> ---
>>  arch/arm/mach-sunxi/mc_smp.c | 5 +++++
>>  1 file changed, 5 insertions(+)
>>
>> diff --git a/arch/arm/mach-sunxi/mc_smp.c b/arch/arm/mach-sunxi/mc_smp.c
>> index 03f021d0c73e..9d57ea27dacc 100644
>> --- a/arch/arm/mach-sunxi/mc_smp.c
>> +++ b/arch/arm/mach-sunxi/mc_smp.c
>> @@ -74,6 +74,7 @@ static void __iomem *sram_b_smp_base;
>>
>>  extern void sunxi_mc_smp_secondary_startup(void);
>>  extern void sunxi_mc_smp_resume(void);
>> +static int is_sun8i;
>>
>>  static bool sunxi_core_is_cortex_a15(unsigned int core, unsigned int cluster)
>>  {
>> @@ -624,6 +625,7 @@ struct sunxi_mc_smp_nodes {
>>  struct sunxi_mc_smp_data {
>>       const char *enable_method;
>>       int (*get_smp_nodes)(struct sunxi_mc_smp_nodes *nodes);
>> +     int is_sun8i;
>>  };
>>
>>  static void __init sunxi_mc_smp_put_nodes(struct sunxi_mc_smp_nodes *nodes)
>> @@ -664,6 +666,7 @@ static const struct sunxi_mc_smp_data sunxi_mc_smp_data[] __initconst = {
>>       {
>>               .enable_method  = "allwinner,sun9i-a80-smp",
>>               .get_smp_nodes  = sun9i_a80_get_smp_nodes,
>> +             .is_sun8i       = false,
>
> I'm still not convinced about the name of that flag. sun8i doesn't
> mean anything, really. What you want to discriminate against it what
> you're writing in your commit log: if it is an A80 or an A83t. The
> A33, H3, A23, you name it are also part of the sun8i family, yet they
> are completely irrelevant to this file.
>
> Also, false is the default value, you can leave it out.
>
>>       },
>>  };
>>
>> @@ -697,6 +700,8 @@ static int __init sunxi_mc_smp_init(void)
>>                       break;
>>       }
>>
>> +     is_sun8i = sunxi_mc_smp_data[i].is_sun8i;
>> +
>
> Do we really need to cache it? Can't we just have a pointer to the SMP
> data structure and use that instead?

I recommended that. We don't need any of the other fields in the SMP
data structure once we're past the init phase. This saves a dereference
or two.

ChenYu