Re: [PATCH RFC 6/7] ARM: shmobile: Do additional settings for L2shutdown mode

[Khiem Nguyen <khiem.nguyen.xt@renesas.com>]

Hi Geert-san,

On 9/26/2014 6:30 PM, Geert Uytterhoeven wrote:
> Hi Khiem-san,
> 
> On Fri, Sep 26, 2014 at 4:40 AM, Khiem Nguyen
> <khiem.nguyen.xt@renesas.com> wrote:
>> According to Cortex-A15 TRM, some additional settings are needed.
>> Although the procedure was not completely same as in TRM, it was
>> referred to vexpress implementation to arrange order of additional
>> settings.
>>
>> Signed-off-by: Khiem Nguyen <khiem.nguyen.xt@renesas.com>
>> ---
>>  arch/arm/mach-shmobile/platsmp-apmu.c |   25 +++++++++++++++++++++++++
>>  1 file changed, 25 insertions(+)
>>
>> diff --git a/arch/arm/mach-shmobile/platsmp-apmu.c b/arch/arm/mach-shmobile/platsmp-apmu.c
>> index dfa8a18..0dedb13 100644
>> --- a/arch/arm/mach-shmobile/platsmp-apmu.c
>> +++ b/arch/arm/mach-shmobile/platsmp-apmu.c
>> @@ -161,8 +161,32 @@ int shmobile_smp_apmu_boot_secondary(unsigned int cpu, struct task_struct *idle)
>>
>>  #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_SUSPEND) || \
>>  defined(CONFIG_CPU_IDLE)
>> +static void do_l2shutdown_settings(void)
>> +{
>> +       unsigned int v;
>> +
>> +       /* Disable L2$ prefetches */
>> +       asm volatile(
>> +       "       mrc     p15, 1, %0, c15, c0, 3\n"
>> +       "       orr     %0, %0, %1\n"
>> +       "       mcr     p15, 1, %0, c15, c0, 3\n"
>> +               : "=&r" (v)
>> +               : "Ir" (0x400)
>> +               : "cc");
>> +       isb();
>> +       dsb();
>> +
>> +       flush_cache_all();
>> +
>> +       /* Set Double lock control bit */
>> +       __asm__ __volatile__("mcr p14, 0, %0, c1, c3, 4" : : "r" (0x1));
>> +}
>> +
>>  static inline void cpu_enter_lowpower_a15(void)
>>  {
>> +       if (is_a15_l2shutdown)
>> +               do_l2shutdown_settings();
>> +
>>         v7_exit_coherency_flush(louis);
>>  }
>>
>> @@ -245,6 +269,7 @@ static int shmobile_smp_apmu_enter_suspend(suspend_state_t state)
>>
>>         writel_relaxed(0x0, cpucmcr);
>>         rcar_sysc_clear_event_status();
>> +       is_a15_l2shutdown = 0;
> 
> What's the purpose of clearing is_a15_l2shutdown here?

As this bit was set in suspend processing,
it should be cleared in resume processing.
And this is to make sure L2shutdown setting is only executed within Suspend-to-RAM,
not CPUIdle/Core-Standby or CPU hotplug. :)

>>
>>         return 0;
>>  }
> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 

-- 
Best regards,
KHIEM Nguyen