bhupesh.sharma at freescale.com
Wed Nov 4 08:18:40 PST 2015
I am trying to build and verify a custom ARM trusted firmware like implementation with
the linux-next to verify if I can use the PSCI interface to get the CPU hotplug
to work (CPU_OFF and CPU_ON sequence).
My EL3 firmware implements the PSCI v0.2 specifications and I enable the same
as the CPU enable_method in the DTS.
Now, while I can get the secondary CPU to shutdown properly via the PSCI implementing
firmware, I cannot seem to get them back-on:
# echo 0 > /sys/devices/system/cpu/cpu2/online
psci: CPU2 killed.
# echo 1 > /sys/devices/system/cpu/cpu2/online
CPU2: failed to come online
I notice that the call to PSCI CPU_ON from kernel returns successfully,
so the EL3 FW returns PSCI_SUCCESS:
static int cpu_psci_cpu_boot(unsigned int cpu)
int err = psci_ops.cpu_on(cpu_logical_map(cpu), __pa(secondary_entry));
pr_err("failed to boot CPU%d (%d)\n", cpu, err);
However, I cannot seem to get the secondaries to enter the 'secondary_entry'
leg, i.e. I cannot see the normal 'CPU%u: Booted secondary processor' prints
* This is the secondary CPU boot entry. We're using this CPUs
* idle thread stack, but a set of temporary page tables.
asmlinkage void secondary_start_kernel(void)
struct mm_struct *mm = &init_mm;
unsigned int cpu = smp_processor_id();
* All kernel threads share the same mm context; grab a
* reference and switch to it.
current->active_mm = mm;
printk("CPU%u: Booted secondary processor\n", cpu);
So, I am wondering if my understanding is correct, as to whether the
secondaries will start execution from __pa(secondary_entry), i.e.
secondary_start_kernel and I should see the above prints in the PSCI CPU_ON case as well,
or is this path only taken in case of a cold boot.
Thanks for any pointers.
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