ARM: shmobile: sh73a0: CPU1 failed to come online (Re: [PATCH 0/4] ARM: shmobile: r8a7740/armadillo: Migrate to generic l2c OF)

[Russell King - ARM Linux]

On Mon, Nov 17, 2014 at 02:57:46PM +0100, Geert Uytterhoeven wrote:
> I tried to convert sh73a0, but it doesn't work, due to problems
> bringing up the second
> CPU core.
> 
> Details:
>   - l2x0_of_init() is called much earlier than l2x0_init().
>     When the L2 cache is enabled, initialization of the second CPU core of
>     sh73a0 (Dual-core Cortex-A9) fails.

Missing L2 cache flushes for (any) the secondary core data/trampoline?

>   - As jiffies are not yet incrementing at that point (they are on r8a7791?),
>     timeouts don't work, and the kernel hangs at the
>     wait_for_completion_timeout() call in arch/arm/kernel/smp.c:__cpu_up().

That sounds bad:

start_kernel() -> rest_init() -> kernel_thread(kernel_init)

kernel_init() -> kernel_init_freeable() -> smp_init() -> (for each CPU) cpu_up()

By the time we get to rest_init(), init_IRQ(), time_init(),
local_irq_enable(), late_time_init(), calibrate_delay(), etc have all
been called, so if jiffies is not incrementing in __cpu_up(), that's
a big problem.

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