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Subject[PATCH v2 09/12] MIPS: pm-cps: Use per-CPU variables as per-CPU, not per-core
Date
From: Paul Burton <paulburton@kernel.org>

The pm-cps code has up until now used per-CPU variables indexed by core,
rather than CPU number, in order to share data amongst sibling CPUs (ie.
VPs/threads in a core). This works fine for single cluster systems, but
with multi-cluster systems a core number is no longer unique in the
system, leading to sharing between CPUs that are not actually siblings.

Avoid this issue by using per-CPU variables as they are more generally
used - ie. access them using CPU numbers rather than core numbers.
Sharing between siblings is then accomplished by:
- Assigning the same pointer to entries for each sibling CPU for the
nc_asm_enter & ready_count variables, which allow this by virtue of
being per-CPU pointers.

- Indexing by the first CPU set in a CPUs cpu_sibling_map in the case
of pm_barrier, for which we can't use the previous approach because
the per-CPU variable is not a pointer.

Signed-off-by: Paul Burton <paulburton@kernel.org>
Signed-off-by: Dragan Mladjenovic <dragan.mladjenovic@syrmia.com>

diff --git a/arch/mips/kernel/pm-cps.c b/arch/mips/kernel/pm-cps.c
index 9bf60d7d44d3..a7bcf2b814c8 100644
--- a/arch/mips/kernel/pm-cps.c
+++ b/arch/mips/kernel/pm-cps.c
@@ -56,10 +56,7 @@ static DEFINE_PER_CPU_ALIGNED(u32*, ready_count);
/* Indicates online CPUs coupled with the current CPU */
static DEFINE_PER_CPU_ALIGNED(cpumask_t, online_coupled);

-/*
- * Used to synchronize entry to deep idle states. Actually per-core rather
- * than per-CPU.
- */
+/* Used to synchronize entry to deep idle states */
static DEFINE_PER_CPU_ALIGNED(atomic_t, pm_barrier);

/* Saved CPU state across the CPS_PM_POWER_GATED state */
@@ -118,9 +115,10 @@ int cps_pm_enter_state(enum cps_pm_state state)
cps_nc_entry_fn entry;
struct core_boot_config *core_cfg;
struct vpe_boot_config *vpe_cfg;
+ atomic_t *barrier;

/* Check that there is an entry function for this state */
- entry = per_cpu(nc_asm_enter, core)[state];
+ entry = per_cpu(nc_asm_enter, cpu)[state];
if (!entry)
return -EINVAL;

@@ -156,7 +154,7 @@ int cps_pm_enter_state(enum cps_pm_state state)
smp_mb__after_atomic();

/* Create a non-coherent mapping of the core ready_count */
- core_ready_count = per_cpu(ready_count, core);
+ core_ready_count = per_cpu(ready_count, cpu);
nc_addr = kmap_noncoherent(virt_to_page(core_ready_count),
(unsigned long)core_ready_count);
nc_addr += ((unsigned long)core_ready_count & ~PAGE_MASK);
@@ -164,7 +162,8 @@ int cps_pm_enter_state(enum cps_pm_state state)

/* Ensure ready_count is zero-initialised before the assembly runs */
WRITE_ONCE(*nc_core_ready_count, 0);
- coupled_barrier(&per_cpu(pm_barrier, core), online);
+ barrier = &per_cpu(pm_barrier, cpumask_first(&cpu_sibling_map[cpu]));
+ coupled_barrier(barrier, online);

/* Run the generated entry code */
left = entry(online, nc_core_ready_count);
@@ -635,12 +634,14 @@ static void *cps_gen_entry_code(unsigned cpu, enum cps_pm_state state)

static int cps_pm_online_cpu(unsigned int cpu)
{
- enum cps_pm_state state;
- unsigned core = cpu_core(&cpu_data[cpu]);
+ unsigned int sibling, core;
void *entry_fn, *core_rc;
+ enum cps_pm_state state;
+
+ core = cpu_core(&cpu_data[cpu]);

for (state = CPS_PM_NC_WAIT; state < CPS_PM_STATE_COUNT; state++) {
- if (per_cpu(nc_asm_enter, core)[state])
+ if (per_cpu(nc_asm_enter, cpu)[state])
continue;
if (!test_bit(state, state_support))
continue;
@@ -652,16 +653,19 @@ static int cps_pm_online_cpu(unsigned int cpu)
clear_bit(state, state_support);
}

- per_cpu(nc_asm_enter, core)[state] = entry_fn;
+ for_each_cpu(sibling, &cpu_sibling_map[cpu])
+ per_cpu(nc_asm_enter, sibling)[state] = entry_fn;
}

- if (!per_cpu(ready_count, core)) {
+ if (!per_cpu(ready_count, cpu)) {
core_rc = kmalloc(sizeof(u32), GFP_KERNEL);
if (!core_rc) {
pr_err("Failed allocate core %u ready_count\n", core);
return -ENOMEM;
}
- per_cpu(ready_count, core) = core_rc;
+
+ for_each_cpu(sibling, &cpu_sibling_map[cpu])
+ per_cpu(ready_count, sibling) = core_rc;
}

return 0;
--
2.17.1
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