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powerpc/book3e: More doorbell cleanups. Sample the PIR register

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The doorbells use the content of the PIR register to match messages
from other CPUs. This may or may not be the same as our linux CPU
number, so using that as the "target" is no right.

Instead, we sample the PIR register at boot on every processor
and use that value subsequently when sending IPIs.

We also use a per-cpu message mask rather than a global array which
should limit cache line contention.

Note: We could use the CPU number in the device-tree instead of
the PIR register, as they are supposed to be equivalent. This
might prove useful if doorbells are to be used to kick CPUs out
of FW at boot time, thus before we can sample the PIR. This is
however not the case now and using the PIR just works.

Signed-off-by: Benjamin Herrenschmidt <benh@kernel.crashing.org>
This commit is contained in:
Benjamin Herrenschmidt 2010-07-09 15:29:53 +10:00
parent e3145b387a
commit b9f1cd71db
3 changed files with 40 additions and 18 deletions
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7
arch/powerpc/include/asm/dbell.h
View File

@ -27,10 +27,9 @@ enum ppc_dbell {
PPC_G_DBELL_MC = 4, /* guest mcheck doorbell */
};
#ifdef CONFIG_SMP
extern unsigned long dbell_smp_message[NR_CPUS];
extern void smp_dbell_message_pass(int target, int msg);
#endif
extern void doorbell_message_pass(int target, int msg);
extern void doorbell_exception(struct pt_regs *regs);
extern void doorbell_setup_this_cpu(void);
static inline void ppc_msgsnd(enum ppc_dbell type, u32 flags, u32 tag)
{

47
arch/powerpc/kernel/dbell.c
View File

@ -13,45 +13,66 @@
#include <linux/kernel.h>
#include <linux/smp.h>
#include <linux/threads.h>
#include <linux/percpu.h>
#include <asm/dbell.h>
#ifdef CONFIG_SMP
unsigned long dbell_smp_message[NR_CPUS];
struct doorbell_cpu_info {
unsigned long messages; /* current messages bits */
unsigned int tag; /* tag value */
};
void smp_dbell_message_pass(int target, int msg)
static DEFINE_PER_CPU(struct doorbell_cpu_info, doorbell_cpu_info);
void doorbell_setup_this_cpu(void)
{
struct doorbell_cpu_info *info = &__get_cpu_var(doorbell_cpu_info);
info->messages = 0;
info->tag = mfspr(SPRN_PIR) & 0x3fff;
}
void doorbell_message_pass(int target, int msg)
{
struct doorbell_cpu_info *info;
int i;
if(target < NR_CPUS) {
set_bit(msg, &dbell_smp_message[target]);
ppc_msgsnd(PPC_DBELL, 0, target);
if (target < NR_CPUS) {
info = &per_cpu(doorbell_cpu_info, target);
set_bit(msg, &info->messages);
ppc_msgsnd(PPC_DBELL, 0, info->tag);
}
else if(target == MSG_ALL_BUT_SELF) {
else if (target == MSG_ALL_BUT_SELF) {
for_each_online_cpu(i) {
if (i == smp_processor_id())
continue;
set_bit(msg, &dbell_smp_message[i]);
ppc_msgsnd(PPC_DBELL, 0, i);
info = &per_cpu(doorbell_cpu_info, i);
set_bit(msg, &info->messages);
ppc_msgsnd(PPC_DBELL, 0, info->tag);
}
}
else { /* target == MSG_ALL */
for_each_online_cpu(i)
set_bit(msg, &dbell_smp_message[i]);
for_each_online_cpu(i) {
info = &per_cpu(doorbell_cpu_info, i);
set_bit(msg, &info->messages);
}
ppc_msgsnd(PPC_DBELL, PPC_DBELL_MSG_BRDCAST, 0);
}
}
void doorbell_exception(struct pt_regs *regs)
{
int cpu = smp_processor_id();
struct doorbell_cpu_info *info = &__get_cpu_var(doorbell_cpu_info);
int msg;
if (num_online_cpus() < 2)
/* Warning: regs can be NULL when called from irq enable */
if (!info->messages || (num_online_cpus() < 2))
return;
for (msg = 0; msg < 4; msg++)
if (test_and_clear_bit(msg, &dbell_smp_message[cpu]))
if (test_and_clear_bit(msg, &info->messages))
smp_message_recv(msg);
}

4
arch/powerpc/platforms/85xx/smp.c
View File

@ -99,6 +99,8 @@ static void __init
smp_85xx_setup_cpu(int cpu_nr)
{
mpic_setup_this_cpu();
if (cpu_has_feature(CPU_FTR_DBELL))
doorbell_setup_this_cpu();
}
struct smp_ops_t smp_85xx_ops = {
@ -117,7 +119,7 @@ void __init mpc85xx_smp_init(void)
}
if (cpu_has_feature(CPU_FTR_DBELL))
smp_85xx_ops.message_pass = smp_dbell_message_pass;
smp_85xx_ops.message_pass = doorbell_message_pass;
BUG_ON(!smp_85xx_ops.message_pass);