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authorRussell King <rmk+kernel@armlinux.org.uk>2018-12-13 17:02:48 +0300
committerRussell King <rmk+kernel@armlinux.org.uk>2019-02-02 01:05:23 +0300
commit6213f70e7c10fd4a01b65bad3826648fc78df8a8 (patch)
treec1296d53776c9668057f570485285754c2424ab5 /arch/arm/mach-prima2
parent70678554c4c40f2cf8de5e7cd53fdd2c73387e51 (diff)
downloadlinux-6213f70e7c10fd4a01b65bad3826648fc78df8a8.tar.xz
ARM: smp: remove arch-provided "pen_release"
Consolidating the "pen_release" stuff amongst the various SoC implementations gives credence to having a CPU holding pen for secondary CPUs. However, this is far from the truth. Many SoC implementations cargo-cult copied various bits of the pen release implementation from the initial Realview/Versatile Express implementation without understanding what it was or why it existed. The reason it existed is because these are _development_ platforms, and some board firmware is unable to individually control the startup of secondary CPUs. Moreover, they do not have a way to power down or reset secondary CPUs for hot-unplug. Hence, the pen_release implementation was designed for ARM Ltd's development platforms to provide a working implementation, even though it is very far from what is required. It was decided a while back to reduce the duplication by consolidating the "pen_release" variable, but this only made the situation worse - we have ended up with several implementations that read this variable but do not write it - again, showing the cargo-cult mentality at work, lack of proper review of new code, and in some cases a lack of testing. While it would be preferable to remove pen_release entirely from the kernel, this is not possible without help from the SoC maintainers, which seems to be lacking. However, I want to remove pen_release from arch code to remove the credence that having it gives. This patch removes pen_release from the arch code entirely, adding private per-SoC definitions for it instead, and explicitly stating that write_pen_release() is cargo-cult copied and should not be copied any further. Rename write_pen_release() in a similar fashion as well. Signed-off-by: Russell King <rmk+kernel@armlinux.org.uk>
Diffstat (limited to 'arch/arm/mach-prima2')
-rw-r--r--arch/arm/mach-prima2/common.h2
-rw-r--r--arch/arm/mach-prima2/headsmp.S2
-rw-r--r--arch/arm/mach-prima2/hotplug.c3
-rw-r--r--arch/arm/mach-prima2/platsmp.c17
4 files changed, 15 insertions, 9 deletions
diff --git a/arch/arm/mach-prima2/common.h b/arch/arm/mach-prima2/common.h
index 6d77b622d168..457eb7b18160 100644
--- a/arch/arm/mach-prima2/common.h
+++ b/arch/arm/mach-prima2/common.h
@@ -15,6 +15,8 @@
#include <asm/mach/time.h>
#include <asm/exception.h>
+extern volatile int prima2_pen_release;
+
extern const struct smp_operations sirfsoc_smp_ops;
extern void sirfsoc_secondary_startup(void);
extern void sirfsoc_cpu_die(unsigned int cpu);
diff --git a/arch/arm/mach-prima2/headsmp.S b/arch/arm/mach-prima2/headsmp.S
index 209d9fc5c16c..6cf4fc60347b 100644
--- a/arch/arm/mach-prima2/headsmp.S
+++ b/arch/arm/mach-prima2/headsmp.S
@@ -34,4 +34,4 @@ ENDPROC(sirfsoc_secondary_startup)
.align
1: .long .
- .long pen_release
+ .long prima2_pen_release
diff --git a/arch/arm/mach-prima2/hotplug.c b/arch/arm/mach-prima2/hotplug.c
index a728c78b996f..b6cf1527e330 100644
--- a/arch/arm/mach-prima2/hotplug.c
+++ b/arch/arm/mach-prima2/hotplug.c
@@ -11,6 +11,7 @@
#include <linux/smp.h>
#include <asm/smp_plat.h>
+#include "common.h"
static inline void platform_do_lowpower(unsigned int cpu)
{
@@ -18,7 +19,7 @@ static inline void platform_do_lowpower(unsigned int cpu)
for (;;) {
__asm__ __volatile__("dsb\n\t" "wfi\n\t"
: : : "memory");
- if (pen_release == cpu_logical_map(cpu)) {
+ if (prima2_pen_release == cpu_logical_map(cpu)) {
/*
* OK, proper wakeup, we're done
*/
diff --git a/arch/arm/mach-prima2/platsmp.c b/arch/arm/mach-prima2/platsmp.c
index 75ef5d4be554..d1f8b5168083 100644
--- a/arch/arm/mach-prima2/platsmp.c
+++ b/arch/arm/mach-prima2/platsmp.c
@@ -24,13 +24,16 @@ static void __iomem *clk_base;
static DEFINE_SPINLOCK(boot_lock);
+/* XXX prima2_pen_release is cargo culted code - DO NOT COPY XXX */
+volatile int prima2_pen_release = -1;
+
static void sirfsoc_secondary_init(unsigned int cpu)
{
/*
* let the primary processor know we're out of the
* pen, then head off into the C entry point
*/
- pen_release = -1;
+ prima2_pen_release = -1;
smp_wmb();
/*
@@ -80,13 +83,13 @@ static int sirfsoc_boot_secondary(unsigned int cpu, struct task_struct *idle)
/*
* The secondary processor is waiting to be released from
* the holding pen - release it, then wait for it to flag
- * that it has been released by resetting pen_release.
+ * that it has been released by resetting prima2_pen_release.
*
- * Note that "pen_release" is the hardware CPU ID, whereas
+ * Note that "prima2_pen_release" is the hardware CPU ID, whereas
* "cpu" is Linux's internal ID.
*/
- pen_release = cpu_logical_map(cpu);
- sync_cache_w(&pen_release);
+ prima2_pen_release = cpu_logical_map(cpu);
+ sync_cache_w(&prima2_pen_release);
/*
* Send the secondary CPU SEV, thereby causing the boot monitor to read
@@ -97,7 +100,7 @@ static int sirfsoc_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 (prima2_pen_release == -1)
break;
udelay(10);
@@ -109,7 +112,7 @@ static int sirfsoc_boot_secondary(unsigned int cpu, struct task_struct *idle)
*/
spin_unlock(&boot_lock);
- return pen_release != -1 ? -ENOSYS : 0;
+ return prima2_pen_release != -1 ? -ENOSYS : 0;
}
const struct smp_operations sirfsoc_smp_ops __initconst = {