[PATCH v4 07/13] ARM: shmobile: apmu: Add APMU DT support via Enable method

[Geert Uytterhoeven]

Hi Sergei,

On Sun, Jun 26, 2016 at 6:36 PM, Sergei Shtylyov
<sergei.shtylyov at cogentembedded.com> wrote:
> On 06/24/2016 10:44 AM, Geert Uytterhoeven wrote:
>>>> From: Magnus Damm <damm+renesas at opensource.se>
>>>> Allow DT configuration of the APMU hardware in the case when the APMU is
>>>> pointed out in the DTB via the enable-method. The ability to configure
>>>> the APMU via C code is still kept intact to prevent DTB breakage for
>>>> older
>>>> SoCs that do not rely on the enable-method for SMP support.
>>>>
>>>> Signed-off-by: Magnus Damm <damm+renesas at opensource.se>
>>>> [geert: Fix CONFIG_SMP=n build]
>>>> Signed-off-by: Geert Uytterhoeven <geert+renesas at glider.be>
>>>
>>> [...]
>>>
>>>> diff --git a/arch/arm/mach-shmobile/platsmp-apmu.c
>>>> b/arch/arm/mach-shmobile/platsmp-apmu.c
>>>> index c1558ef0c590dd3e..0c6bb458b7a45128 100644
>>>> --- a/arch/arm/mach-shmobile/platsmp-apmu.c
>>>> +++ b/arch/arm/mach-shmobile/platsmp-apmu.c
>>>
>>> [...]
>>>>
>>>>
>>>> +static int shmobile_smp_apmu_boot_secondary_md21(unsigned int cpu,
>>>> +                                                struct task_struct
>>>> *idle)
>>>> +{
>>>> +       /* Error out when hardware debug mode is enabled */
>>>> +       if (rcar_gen2_read_mode_pins() & BIT(21)) {
>>>> +               pr_warn("Unable to boot CPU%u when MD21 is set\n", cpu);
>>>> +               return -ENOTSUPP;
>>>> +       }
>>>> +
>>>> +       return shmobile_smp_apmu_boot_secondary(cpu, idle);
>>>> +}
>>>> +
>>>> +static struct smp_operations apmu_smp_ops __initdata = {
>>>> +       .smp_prepare_cpus       = shmobile_smp_apmu_prepare_cpus_dt,
>>>> +       .smp_boot_secondary     = shmobile_smp_apmu_boot_secondary_md21,
>>>> +#ifdef CONFIG_HOTPLUG_CPU
>>>> +       .cpu_can_disable        = shmobile_smp_cpu_can_disable,
>>>> +       .cpu_die                = shmobile_smp_apmu_cpu_die,
>>>> +       .cpu_kill               = shmobile_smp_apmu_cpu_kill,
>>>>  #endif
>>>
>>>    For the record: it turned out that I tested my non-DT SMP on
>>> R8A7792/Blanche with MD21 bit set. And I've just made sure it still works
>>> with this implementation (by commenting out the check above.
>>>    Also, I was going to try the workaround for MD21 I saw in the BSP tree
>>> --
>
>> Which workaround? I only saw the BSP removed the check, but it didn't
>> mention
>> why (because E2 and V2H don't need it, or...?).
>
>    I'm looking at the <soc>_smp_prepare_cpus() in
> arch/arm/mach-shmobile/setup-<soc>.c in the

.../smp-<soc>.c

> 'bsp/v3.10.31-ltsi/rcar-gen2-1.9.6' branch of Simon's renesas-backport.git.
> The all have the code to handle MD21 bit set (by setting some bits in
> CA{7,15}DBGRCR.
>
>>> perhaps it'll help get R8A7791 working w/MD21 set...

Thanks! I'll give that a try...

Note that for SoCs with CA7 cores, it sets undocumented bits (the 0x3330 part)?

For now we can keep the check, as the behavior is the same as on H2/M2-W
before, so it doesn't introduce a regression.

>> Does your Porter work with the other MD21 setting (and the check commented
>> out, of coutse)?
>
>    Yes, I've made sure it works now.

With or without the DBGRCR code from the BSP?

Thanks!

Gr{oetje,eeting}s,

                        Geert

--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert at 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