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ARM: versatile: rename and comment SMP implementation 

Rename pen_release and boot_lock in the Versatile specific SMP
implementation, describe why these exist and state clearly that they
should not be used in production implementations.

Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
This commit is contained in:
Russell King 2018-12-13 12:54:26 +00:00
parent 830eec2467
commit d9b778e7bf
4 changed files with 38 additions and 16 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

2
arch/arm/plat-versatile/headsmp.S
View File

@ -37,5 +37,5 @@ pen: ldr r7, [r6]
.align
1: .long .
.long pen_release
.long versatile_cpu_release
ENDPROC(versatile_secondary_startup)

4
arch/arm/plat-versatile/hotplug.c
View File

@ -18,6 +18,8 @@
#include <asm/smp_plat.h>
#include <asm/cp15.h>
#include <plat/platsmp.h>
static inline void versatile_immitation_enter_lowpower(unsigned int actrl_mask)
{
unsigned int v;
@ -67,7 +69,7 @@ static inline void versatile_immitation_do_lowpower(unsigned int cpu, int *spuri
for (;;) {
wfi();
if (pen_release == cpu_logical_map(cpu)) {
if (versatile_cpu_release == cpu_logical_map(cpu)) {
/*
* OK, proper wakeup, we're done
*/

1
arch/arm/plat-versatile/include/plat/platsmp.h
View File

@ -8,6 +8,7 @@
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*/
extern volatile int versatile_cpu_release;
extern void versatile_secondary_startup(void);
extern void versatile_secondary_init(unsigned int cpu);

47
arch/arm/plat-versatile/platsmp.c
View File

@ -7,6 +7,11 @@
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This code is specific to the hardware found on ARM Realview and
* Versatile Express platforms where the CPUs are unable to be individually
* woken, and where there is no way to hot-unplug CPUs. Real platforms
* should not copy this code.
*/
#include <linux/init.h>
#include <linux/errno.h>
@ -21,18 +26,32 @@
#include <plat/platsmp.h>
/*
* Write pen_release in a way that is guaranteed to be visible to all
* observers, irrespective of whether they're taking part in coherency
* versatile_cpu_release controls the release of CPUs from the holding
* pen in headsmp.S, which exists because we are not always able to
* control the release of individual CPUs from the board firmware.
* Production platforms do not need this.
*/
volatile int versatile_cpu_release = -1;
/*
* Write versatile_cpu_release in a way that is guaranteed to be visible to
* all observers, irrespective of whether they're taking part in coherency
* or not. This is necessary for the hotplug code to work reliably.
*/
static void write_pen_release(int val)
static void versatile_write_cpu_release(int val)
{
pen_release = val;
versatile_cpu_release = val;
smp_wmb();
sync_cache_w(&pen_release);
sync_cache_w(&versatile_cpu_release);
}
static DEFINE_RAW_SPINLOCK(boot_lock);
/*
* versatile_lock exists to avoid running the loops_per_jiffy delay loop
* calibrations on the secondary CPU while the requesting CPU is using
* the limited-bandwidth bus - which affects the calibration value.
* Production platforms do not need this.
*/
static DEFINE_RAW_SPINLOCK(versatile_lock);
void versatile_secondary_init(unsigned int cpu)
{
@ -40,13 +59,13 @@ void versatile_secondary_init(unsigned int cpu)
* let the primary processor know we're out of the
* pen, then head off into the C entry point
*/
write_pen_release(-1);
versatile_write_cpu_release(-1);
/*
* Synchronise with the boot thread.
*/
raw_spin_lock(&boot_lock);
raw_spin_unlock(&boot_lock);
raw_spin_lock(&versatile_lock);
raw_spin_unlock(&versatile_lock);
}
int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
@ -57,7 +76,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
* Set synchronisation state between this boot processor
* and the secondary one
*/
raw_spin_lock(&boot_lock);
raw_spin_lock(&versatile_lock);
/*
* This is really belt and braces; we hold unintended secondary
@ -65,7 +84,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
* since we haven't sent them a soft interrupt, they shouldn't
* be there.
*/
write_pen_release(cpu_logical_map(cpu));
versatile_write_cpu_release(cpu_logical_map(cpu));
/*
* Send the secondary CPU a soft interrupt, thereby causing
@ -77,7 +96,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
timeout = jiffies + (1 * HZ);
while (time_before(jiffies, timeout)) {
smp_rmb();
if (pen_release == -1)
if (versatile_cpu_release == -1)
break;
udelay(10);
@ -87,7 +106,7 @@ int versatile_boot_secondary(unsigned int cpu, struct task_struct *idle)
* now the secondary core is starting up let it run its
* calibrations, then wait for it to finish
*/
raw_spin_unlock(&boot_lock);
raw_spin_unlock(&versatile_lock);
return pen_release != -1 ? -ENOSYS : 0;
return versatile_cpu_release != -1 ? -ENOSYS : 0;
}