ARM: versatile: rename and comment Versatile specific SMP implementation
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Message ID E1gXQKg-0007WS-1q@rmk-PC.armlinux.org.uk
State New
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  • ARM: versatile: rename and comment Versatile specific SMP implementation
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Commit Message

Russell King Dec. 13, 2018, 12:43 p.m. UTC
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>
---
 arch/arm/plat-versatile/headsmp.S              |  2 +-
 arch/arm/plat-versatile/hotplug.c              |  4 ++-
 arch/arm/plat-versatile/include/plat/platsmp.h |  1 +
 arch/arm/plat-versatile/platsmp.c              | 47 ++++++++++++++++++--------
 4 files changed, 38 insertions(+), 16 deletions(-)

Comments

Russell King - ARM Linux admin Dec. 13, 2018, 12:51 p.m. UTC | #1
On Thu, Dec 13, 2018 at 12:43:14PM +0000, Russell King wrote:
> 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>

With this patch in place, the pen_release prototype and definition in
the core arch code (that was IMHO inappropriately consolidated as it
gives credence to its use - but now proves to be an advantage) _could_
be marked with __deprecated as a motivation for exynos, prima2 and spear
SoC maintainers to fix their remaining uses of the pen_release stuff.

That's also three of the five remaining platforms that make use of
boot_lock.

Of course, with the change of _this_ boot_lock to a raw spinlock, this
patch will need to be updated for that change.

> ---
>  arch/arm/plat-versatile/headsmp.S              |  2 +-
>  arch/arm/plat-versatile/hotplug.c              |  4 ++-
>  arch/arm/plat-versatile/include/plat/platsmp.h |  1 +
>  arch/arm/plat-versatile/platsmp.c              | 47 ++++++++++++++++++--------
>  4 files changed, 38 insertions(+), 16 deletions(-)
> 
> diff --git a/arch/arm/plat-versatile/headsmp.S b/arch/arm/plat-versatile/headsmp.S
> index 40f27e52de75..e99396dfa6f3 100644
> --- a/arch/arm/plat-versatile/headsmp.S
> +++ b/arch/arm/plat-versatile/headsmp.S
> @@ -37,5 +37,5 @@ pen:	ldr	r7, [r6]
>  
>  	.align
>  1:	.long	.
> -	.long	pen_release
> +	.long	versatile_cpu_release
>  ENDPROC(versatile_secondary_startup)
> diff --git a/arch/arm/plat-versatile/hotplug.c b/arch/arm/plat-versatile/hotplug.c
> index e2d3e9035d0f..c974958417fe 100644
> --- a/arch/arm/plat-versatile/hotplug.c
> +++ b/arch/arm/plat-versatile/hotplug.c
> @@ -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
>  			 */
> diff --git a/arch/arm/plat-versatile/include/plat/platsmp.h b/arch/arm/plat-versatile/include/plat/platsmp.h
> index 9fff1f241c9e..1b087fbbc700 100644
> --- a/arch/arm/plat-versatile/include/plat/platsmp.h
> +++ b/arch/arm/plat-versatile/include/plat/platsmp.h
> @@ -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);
> diff --git a/arch/arm/plat-versatile/platsmp.c b/arch/arm/plat-versatile/platsmp.c
> index c2366510187a..6fee8df9591a 100644
> --- a/arch/arm/plat-versatile/platsmp.c
> +++ b/arch/arm/plat-versatile/platsmp.c
> @@ -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_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_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.
>  	 */
> -	spin_lock(&boot_lock);
> -	spin_unlock(&boot_lock);
> +	spin_lock(&versatile_lock);
> +	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
>  	 */
> -	spin_lock(&boot_lock);
> +	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
>  	 */
> -	spin_unlock(&boot_lock);
> +	spin_unlock(&versatile_lock);
>  
> -	return pen_release != -1 ? -ENOSYS : 0;
> +	return versatile_cpu_release != -1 ? -ENOSYS : 0;
>  }
> -- 
> 2.7.4
>

Patch
diff mbox series

diff --git a/arch/arm/plat-versatile/headsmp.S b/arch/arm/plat-versatile/headsmp.S
index 40f27e52de75..e99396dfa6f3 100644
--- a/arch/arm/plat-versatile/headsmp.S
+++ b/arch/arm/plat-versatile/headsmp.S
@@ -37,5 +37,5 @@  pen:	ldr	r7, [r6]
 
 	.align
 1:	.long	.
-	.long	pen_release
+	.long	versatile_cpu_release
 ENDPROC(versatile_secondary_startup)
diff --git a/arch/arm/plat-versatile/hotplug.c b/arch/arm/plat-versatile/hotplug.c
index e2d3e9035d0f..c974958417fe 100644
--- a/arch/arm/plat-versatile/hotplug.c
+++ b/arch/arm/plat-versatile/hotplug.c
@@ -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
 			 */
diff --git a/arch/arm/plat-versatile/include/plat/platsmp.h b/arch/arm/plat-versatile/include/plat/platsmp.h
index 9fff1f241c9e..1b087fbbc700 100644
--- a/arch/arm/plat-versatile/include/plat/platsmp.h
+++ b/arch/arm/plat-versatile/include/plat/platsmp.h
@@ -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);
diff --git a/arch/arm/plat-versatile/platsmp.c b/arch/arm/plat-versatile/platsmp.c
index c2366510187a..6fee8df9591a 100644
--- a/arch/arm/plat-versatile/platsmp.c
+++ b/arch/arm/plat-versatile/platsmp.c
@@ -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_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_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.
 	 */
-	spin_lock(&boot_lock);
-	spin_unlock(&boot_lock);
+	spin_lock(&versatile_lock);
+	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
 	 */
-	spin_lock(&boot_lock);
+	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
 	 */
-	spin_unlock(&boot_lock);
+	spin_unlock(&versatile_lock);
 
-	return pen_release != -1 ? -ENOSYS : 0;
+	return versatile_cpu_release != -1 ? -ENOSYS : 0;
 }