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ARM: bL_switcher: synchronize the outbound with the inbound

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Let's wait for the inbound CPU to come up and snoop some of the outbound
CPU cache before bringing the outbound CPU down.  That should be more
efficient than going down right away.

Possible improvements might involve some monitoring of the CCI event
counters.

Signed-off-by: Nicolas Pitre <nico@linaro.org>
This commit is contained in:
Nicolas Pitre 2012-10-23 01:39:08 -04:00
parent 0577fee283
commit 108a9640ab
1 changed files with 22 additions and 2 deletions
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24
arch/arm/common/bL_switcher.c
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@ -55,9 +55,10 @@ static int read_mpidr(void)
* bL switcher core code.
*/
static void bL_do_switch(void *_unused)
static void bL_do_switch(void *_arg)
{
unsigned ib_mpidr, ib_cpu, ib_cluster;
long volatile handshake, **handshake_ptr = _arg;
pr_debug("%s\n", __func__);
@ -65,6 +66,13 @@ static void bL_do_switch(void *_unused)
ib_cpu = MPIDR_AFFINITY_LEVEL(ib_mpidr, 0);
ib_cluster = MPIDR_AFFINITY_LEVEL(ib_mpidr, 1);
/* Advertise our handshake location */
if (handshake_ptr) {
handshake = 0;
*handshake_ptr = &handshake;
} else
handshake = -1;
/*
* Our state has been saved at this point. Let's release our
* inbound CPU.
@ -83,6 +91,14 @@ static void bL_do_switch(void *_unused)
* we have none.
*/
/*
* Let's wait until our inbound is alive.
*/
while (!handshake) {
wfe();
smp_mb();
}
/* Let's put ourself down. */
mcpm_cpu_power_down();
@ -130,6 +146,7 @@ static int bL_switch_to(unsigned int new_cluster_id)
unsigned int ob_mpidr, ob_cpu, ob_cluster, ib_mpidr, ib_cpu, ib_cluster;
struct tick_device *tdev;
enum clock_event_mode tdev_mode;
long volatile *handshake_ptr;
int ret;
this_cpu = smp_processor_id();
@ -198,7 +215,7 @@ static int bL_switch_to(unsigned int new_cluster_id)
cpu_logical_map(that_cpu) = ob_mpidr;
/* Let's do the actual CPU switch. */
ret = cpu_suspend(0, bL_switchpoint);
ret = cpu_suspend((unsigned long)&handshake_ptr, bL_switchpoint);
if (ret > 0)
panic("%s: cpu_suspend() returned %d\n", __func__, ret);
@ -220,6 +237,9 @@ static int bL_switch_to(unsigned int new_cluster_id)
local_fiq_enable();
local_irq_enable();
*handshake_ptr = 1;
dsb_sev();
if (ret)
pr_err("%s exiting with error %d\n", __func__, ret);
return ret;